Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

Resolve onboard the X-ray satellite XRISM is a cryogenic instrument with an X-ray microcalorimeter in a Dewar. A lid partially transparent to X-rays is installed at the top of the Dewar along the optical axis, which is called the gate valve (GV). Because observations will be made through the GV for the first few months, the X-ray transmission calibration of the GV is crucial for initial scientific outcomes. We present the results of our ground calibration campaign of the GV, which is composed of a Be window and a stainless steel mesh. For the stainless steel mesh, we measured its transmission using the X-ray beamline at ISAS for the first time. For the Be window, we used synchrotron facilities to measure the transmission and modeled the data with (i) photoelectric absorption and incoherent scattering of Be, (ii) photoelectric absorption of contaminants, and (iii) coherent scattering of Be. We discuss the physical interpretation of the transmission discontinuity caused by the Bragg diffraction in poly-crystal Be, which we incorporated into our phenomenological model. The measurements and the constructed model meet the calibration requirements of the GV. We also performed a spectral fitting of the Crab nebula data observed with Hitomi SXS and confirmed improvements of the model.

DOI： 10.1117/12.2559451

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Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

© 2020 SPIE The X-Ray Imaging and Spectroscopy Mission (XRISM) is the successor to the 2016 Hitomi mission that ended prematurely. Like Hitomi, the primary science goals are to examine astrophysical problems with precise high-resolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. XRISM carries a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly and a co-aligned X-ray CCD camera that covers the same energy band over a large field of view. XRISM utilizes Hitomi heritage, but all designs were reviewed. The attitude and orbit control system were improved in hardware and software. The number of star sensors were increased from two to three to improve coverage and robustness in onboard attitude determination and to obtain a wider field of view sun sensor. The fault detection, isolation, and reconfiguration (FDIR) system was carefully examined and reconfigured. Together with a planned increase of ground support stations, the survivability of the spacecraft is significantly improved.

DOI： 10.1117/12.2565812

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.cryogenics.2019.103016

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Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/1538-4357/ab2b3d

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Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/ab2b3d

Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

The accretion-induced pulse period changes of the Be/X-ray binary pulsar X Persei were investigated over the period of 1996 January to 2017 September. This study utilized the monitoring data acquired with the RXTE All-Sky Monitor in 1.5–12 keV and the MAXI Gas-Slit Camera in 2–20 keV. The source intensity changed by a factor of 5–6 over this period. The pulsar was spinning down for 1996–2003, and has been spinning up since 2003, as already reported. The spin-up/down rate and the 3–12 keV flux, determined every 250 d, showed a clear negative correlation, which can be successfully explained by the accretion torque model proposed by Ghosh and Lamb (1979, ApJ, 234, 296). When the mass, radius, and distance of the neutron star were allowed to vary over a range of 1.0–2.4 solar masses, 9.5–15 km, and 0.77–0.85 kpc, respectively, the magnetic field strength of B = (4–25) × 1013 G gave the best fits to the observations. In contrast, the observed results cannot be explained by the values of B ∼ 1012 G previously suggested for X Persei, as long as the mass, radius, and distance are required to take reasonable values. Assuming a distance of 0.81 ± 0.04 kpc as indicated by optical astrometry, the mass of the neutron star is estimated as M = 2.03 ± 0.17 solar masses.

DOI： 10.1093/pasj/psy088

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：the Astronomical Society of Japan  

We present results from the Hitomi X-ray observation of a young composite-type supernova remnant (SNR) G21.5−0.9, whose emission is dominated by the pulsar wind nebula (PWN) contribution. The X-ray spectra in the 0.8–80 keV range obtained with the Soft X-ray Spectrometer (SXS), Soft X-ray Imager, and Hard X-ray Imager (HXI) show a significant break in the continuum as previously found with the NuSTAR observation. After taking into account all known emissions from the SNR other than the PWN itself, we find that the Hitomi spectra can be fitted with a broken power law with photon indices of Γ1 = 1.74 ± 0.02 and Γ2 = 2.14 ± 0.01 below and above the break at 7.1 ± 0.3 keV, which is significantly lower than the NuSTAR result (∼9.0 keV). The spectral break cannot be reproduced by time-dependent particle injection one-zone spectral energy distribution models, which strongly indicates that a more complex emission model is needed, as suggested by recent theoretical models. We also search for narrow emission or absorption lines with the SXS, and perform a timing analysis of PSR J1833−1034 with the HXI and the Soft Gamma-ray Detector. No significant pulsation is found from the pulsar. However, unexpectedly, narrow absorption line features are detected in the SXS data at 4.2345 keV and 9.296 keV with a significance of 3.65 σ. While the origin of these features is not understood, their mere detection opens up a new field of research and was only possible with the high resolution, sensitivity, and ability to measure extended sources provided by an X-ray microcalorimeter.

DOI： 10.1093/pasj/psy027

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：the Astronomical Society of Japan,  

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DOI： 10.1117/1.JATIS.4.2.021406

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Other Link： http://orcid.org/0000-0002-2374-7073

© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). The soft x-ray spectrometer (SXS) was a cryogenic high-resolution x-ray spectrometer onboard the Hitomi (ASTRO-H) satellite that achieved energy resolution of 5 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from room temperature to the ADR heat sink was composed of two-stage Stirling cryocoolers, a4He Joule-Thomson cryocooler, and superfluid liquid helium and was installed in a dewar. It was designed to achieve a helium lifetime of more than 3 years with a minimum of 30 L. The satellite was launched on February 17, 2016, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the helium tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and the cryocoolers.

DOI： 10.1117/1.JATIS.4.1.011208

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The X-ray line diagnostic method is a powerful tool for an investigation of plasma around accretion-powered X-ray pulsars. We point out an apparent intensity modulation of emission lines, with their rotation period of neutron stars, due to the finite speed of light ( we call this effect the "finite light speed effect") if the line emission mechanism is a kind of reprocessing, such as fluorescence or recombination after ionization by X-ray irradiation from pulsars. The modulation amplitude is determined by the size of the emission region, which is in competition with the smearing effect by the light crossing time in the emission region. This is efficient if the size of the emission region is roughly comparable to that of the rotation period multiplied by the speed of light. We apply this effect to a symbiotic X-ray pulsar, GX 1+4, where a spin modulation of the intense iron line of which has been reported. The finite light speed effect can explain the observed intensity modulation if its fluorescent region is the size of similar to 10(12) cm.

DOI： 10.3847/1538-4357/aa9023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae(1). Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode(2-6). Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun(7-11), suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, highresolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations(12-14) disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near-and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment(5,15,16).

DOI： 10.1038/nature24301

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

The black hole binary Cygnus X-1 has a 5.6-d orbital period. We first detected a clear intensity modulation with the orbital period in its high/soft state with six-year MAXI data, as well as in its low/hard state. In the low/hard state, the folded light curves showed an intensity drop at the superior conjunction of the black hole by a modulation factor (MF), which is the amplitude divided by the average, of 8 +/- 1%, 4 +/- 1%, and 3 +/- 2% for 2-4, 4-10, and 10-20 keV bands, respectively, showing a spectral hardening at the superior conjunction of the black hole. Spectral analysis in the low/hard state, with a model consisting of a power law and a photoelectric absorption, showed that the hydrogen column density, NH, increased from (2.9 +/- 0.4) x 10(21) cm(-2) to (4.7 +/- 1.1) x 10(21) cm(-2) around the superior conjunction. The flux of the power-law component decreased by 6 +/- 1%. On the other hand, MFs for the folded light curves in the high/soft state, were 4 +/- 1% and 4 +/- 2% for the 2-4 keV and 4-10 keV bands, respectively. We applied a model consisting of a power law and a disk blackbody with a photoelectric absorption. A modulation of the flux of the power-law component was found to be 7 +/- 5% in MF, while the modulation of NH was less than 1 x 10(21) cm(-2). These results can be interpreted as follows: the modulation of both states can be mainly explained by scattering of X-rays by an ionized stellar wind, but, only at the superior conjunction in the low/hard state, a large photoelectric absorption appears because of the low ionization state of the wind in the line of sight at phase 0. Such a condition can be established by reasonable parameters of an inhomogeneous wind and the observed luminosities.

DOI： 10.1093/pasj/psx028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E approximate to 3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S XVI (E similar or equal to 3.44 keV rest-frame)-a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.

DOI： 10.3847/2041-8213/aa61fa

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We present results obtained from a Suzaku observation of the accretion-powered X-ray pulsar GX. 1+ 4. A broadband continuum spectrum of the pulsar was found to be better described by a simple model consisting of a blackbody component and an exponential cutoff power law than the previously used compTT continuum model. Though the pulse profile had a sharp dip in soft X-rays (< 10 keV), phase-resolved spectroscopy confirmed that the dimming was not due to an increase in photoelectric absorption. Phase-sliced spectral analysis showed the presence of a significant spectral modulation beyond 10 keV except for the dip phase. A search for the presence of a cyclotron resonance scattering feature in the Suzaku spectra yielded a negative result. Iron K-shell (Ka and Kb) emission lines from nearly neutral iron ions (< Fe III) were clearly detected in the source spectrum. A significant Ka emission line from almost neutral Ni atoms was detected for the first time in this source. We estimated an iron abundance of similar to 80% of the solar value and an Ni/Fe abundance ratio of about two times the solar value. We searched for an iron Lya emission line and found a significant improvement in the spectral fitting by inclusion of this line. We found a clear intensity modulation of the iron Ka line with the pulse phase with an amplitude of 7%. This finding favored an inhomogeneous fluorescent region with a radius much smaller than the size (similar to 3. x. 10(12) cm) estimated by an assumption of homogeneous matter.

DOI： 10.3847/1538-4357/aa6301

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Clusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes(1) of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling-a process known as active galactic nucleus feedback(2-6). Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 +/- 10 kilometres per second in the region 30-60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 +/- 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.

DOI： 10.1038/nature18627

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Astronomical Society of Japan  

© 2016 The Author. The long-term X-ray variability of the black hole binary Cygnus X-1 was studied with five years of MAXI data from 2009 to 2014, which include substantial periods of the high/soft state, as well as the low/hard state. In each state, normalized power spectrum densities (NPSDs) were calculated in three energy bands of 2-4 keV, 4-10 keV, and 10-20 keV. The NPSDs for frequencies from 10 -7 Hz to 10 -4 Hz are all approximated by a power-law function with an index -1.35-1.29. The fractional RMS variation η, calculated in the above frequency range, was found to show the following three properties: (1) η slightly decreases with energy in the low/hard state; (2) η increases towards higher energies in the high/soft state; and (3) in the 10-20 keV band, η is three times higher in the high/soft state than in the low/hard state. These properties were confirmed through studies of intensity-correlated changes of the MAXI spectra. Of these three findings, the first one is consistent with that seen in the short-term variability during the low/hard state. The latter two can be understood as a result of high variability of the hard-tail component seen in the high/soft state with the above very low frequency range, although the origin of the variability remains inconclusive.

DOI： 10.1093/pasj/psw004

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.71.1.0_509

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_367

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© 2016 SPIE. The Soft X-ray Spectrometer (SXS) is a cryogenic high-resolution X-ray spectrometer onboard the ASTRO-H satellite, that achieves energy resolution better than 7 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator. The cooling chain from room temperature to the ADR heat sink is composed of 2-stage Stirling cryocoolers, a 4He Joule-Thomson cryocooler, and super uid liquid He, and is installed in a dewar. It is designed to achieve a helium lifetime of more than 3 years with a minimum of 30 liters. The satellite was launched on 2016 February 17, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the He tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and cryocoolers.

DOI： 10.1117/12.2232933

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We present the overall design and performance of the Astro-H (Hitomi) Soft X-Ray Spectrometer (SXS). The instrument uses a 36-pixel array of x-ray microcalorimeters at the focus of a grazing-incidence x-ray mirror Soft X-Ray Telescope (SXT) for high-resolution spectroscopy of celestial x-ray sources. The instrument was designed to achieve an energy resolution better than 7 eV over the 0.3-12 keV energy range and operate for more than 3 years in orbit. The actual energy resolution of the instrument is 4-5 eV as demonstrated during extensive ground testing prior to launch and in orbit. The measured mass flow rate of the liquid helium cryogen and initial fill level at launch predict a lifetime of more than 4 years assuming steady mechanical cooler performance. Cryogen-free operation was successfully demonstrated prior to launch. The successful operation of the SXS in orbit, including the first observations of the velocity structure of the Perseus cluster of galaxies, demonstrates the viability and power of this technology as a tool for astrophysics.

DOI： 10.1117/12.2232509

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We summarize all the in-orbit operations of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H (Hitomi) satellite. The satellite was launched on 2016/02/17 and the communication with the satellite ceased on 2016/03/26. The SXS was still in the commissioning phase, in which the setups were progressively changed. This article is intended to serve as a reference of the events in the orbit to properly interpret the SXS data taken during its short life time, and as a test case for planning the in-orbit operation for future micro-calorimeter missions.

DOI： 10.1117/12.2231784

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

A rather strong mean longitudinal magnetic field of the order of a few hundred gauss was detected a few years ago in the Of?p star CPD -28 degrees 2561 using FORS2 (FOcal Reducer low dispersion Spectrograph 2) low-resolution spectropolarimetric observations. In this work, we present additional low-resolution spectropolarimetric observations obtained during several weeks in 2013 December using FORS 2 mounted at the 8-m Antu telescope of the Very Large Telescope (VLT). These observations cover a little less than half of the stellar rotation period of 73.41 d mentioned in the literature. The behaviour of the mean longitudinal magnetic field is consistent with the assumption of a single-wave variation during the stellar rotation cycle, indicating a dominant dipolar contribution to the magnetic field topology. The estimated polar strength of the surface dipole B-d is larger than 1.15 kG. Further, we compared the behaviour of the line profiles of various elements at different rotation phases associated with different magnetic field strengths. The strongest contribution of the emission component is observed at the phases when the magnetic field shows a negative or positive extremum. The comparison of the spectral behaviour of CPD -28 degrees 2561 with that of another Of?p star, HD 148937 of similar spectral type, reveals remarkable differences in the degree of variability between both stars. Finally, we present new X-ray observations obtained with the Suzaku X-ray Observatory. We report that the star is X-ray bright with log L-X/L-bol approximate to -5.7. The low-resolution X-ray spectra reveal the presence of a plasma heated up to 24 MK. We associate the 24 MK plasma in CPD -28 degrees 2561 with the presence of a kG strong magnetic field capable to confine stellar wind.

DOI： 10.1093/mnras/stu2516

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_471

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_500

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DOI： 10.1063/1.4885468

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We report on the Suzaku detection of a rapid flare-like X-ray flux amplification early in the development of the classical nova V2672 Ophiuchi. Two target-of-opportunity similar to 25 ks X-ray observations were made 12 and 22 d after the outburst. The flux amplification was found in the latter half of day 12. Time-sliced spectra are characterized by a growing supersoft excess with edge-like structures and a relatively stable optically-thin thermal component with K alpha emission lines from highly ionized Si. The observed spectral evolution is consistent with a model that has a time development of circumstellar absorption, for which we obtained a decline rate of similar to 10%-40% on a time scale of 0.2 d on day 12. Such a rapid drop of absorption and short-term flux variability on day 12 suggests inhomogeneous ejecta with dense blobs/holes in the line-of-sight. Then on day 22 the fluxes of both supersoft and thin-thermal plasma components became significantly fainter. Based on the serendipitous results we discuss the nature of this source in the context of both short- and long-term X-ray behavior.

DOI： 10.1093/pasj/psu019

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Publishing type：Research paper (international conference proceedings)  

PolariS (Polarimetry Satellite) is a Japanese small satellite mission dedicated to polarimetry of X-ray and γ-ray sources. The primary aim of the mission is to perform hard X-ray (10-80 keV) polarimetry of sources brighter than 10 mCrab. For this purpose, PolariS employs three hard X-ray telescopes and scattering type imaging polarimeters. PolariS will measure the X-ray polarization for tens of sources including extragalactic ones mostly for the first time. The second purpose of the mission is γ-ray polarimetry of transient sources, such as γ-ray bursts (GRBs). Wide field polarimeters based on similar concept as that used in the IKAROS/GAP but with higher sensitivity will be used, and polarization measurement of 10 GRBs per year is expected.

DOI： 10.1117/12.2056685

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

PolariS (Polarimetry Satellite) is a Japanese small satellite mission dedicated to polarimetry of X-ray and gamma-ray sources. The primary aim of the mission is to perform hard X-ray (10-80 keV) polarimetry of sources brighter than 10 mCrab. For this purpose, PolariS employs three hard X-ray telescopes and scattering type imaging polarimeters. PolariS will measure the X-ray polarization for tens of sources including extragalactic ones mostly for the first time. The second purpose of the mission is gamma-ray polarimetry of transient sources, such as gamma-ray bursts (GRBs). Wide field polarimeters based on similar concept as that used in the IKAROS/GAP but with higher sensitivity will be used, and polarization measurement of 10 GRBs per year is expected.

DOI： 10.1117/12.2056685

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We present the development status of the Soft X-ray Spectrometer (SXS) onboard the ASTRO-H mission. The SXS provides the capability of high energy-resolution X-ray spectroscopy of a FWHM energy resolution of < 7eV in the energy range of 0.3 - 10 keV. It utilizes an X-ray micorcalorimeter array operated at 50 mK. The SXS microcalorimeter subsystem is being developed in an EM-FM approach. The EM SXS cryostat was developed and fully tested and, although the design was generally confirmed, several anomalies and problems were found. Among them is the interference of the detector with the micro-vibrations from the mechanical coolers, which is the most difficult one to solve. We have pursued three different countermeasures and two of them seem to be effective. So far we have obtained energy resolutions satisfying the requirement with the FM cryostat.

DOI： 10.1117/12.2057199

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Language：English   Publishing type：Research paper (scientific journal)  

We report the Suzaku detection of the earliest X-ray eclipse seen in the recurrent nova U Scorpii 2010. A target-of-opportunity observation 15 days after the outburst found a 27% ± 5% dimming in the 0.2-1.0 keV energy band at the predicted center of an eclipse. In comparison with the X-ray eclipse depths seen at two later epochs by XMM-Newton, the source region shrank by about 10%-20% between days 15 and 35 after the outburst. The X-ray eclipses appear to be deeper than or similar to contemporaneous optical eclipses, suggesting the X-ray and optical source region extents are comparable on day 15. We raise the possibility of the energy dependency in the photon escape regions, and that this would be a result of the supersoft X-ray opacity being higher than the Thomson scattering opacity at the photosphere due to bound-free transitions in abundant metals that are not fully ionized. Assuming a spherically symmetric model, we constrain the mass-loss rate as a function of time. For a ratio of actual to Thomson opacity of 10-100 in supersoft X-rays, we find an ejecta mass of about 10-7-10-6 M . © 2013. The American Astronomical Society. All rights reserved..

DOI： 10.1088/2041-8205/769/1/L4

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Language：English   Publisher：Astronomical Society of Japan  

DOI： 10.1093/pasj/64.5.101

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DOI： 10.1007/s10909-012-0482-1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We report our examination of a new X-ray interferometer for observation of celestial objects and our recent work for preparation of laboratory experiments. The new X-ray interferometer is consisting of two flat mirrors and one flat beam splitter which are used as grazing incident optics. The aimed wave length is a O-K band or a C-K band. The beam splitter and the mirrors are fabricated by Mo/Si multilayer. We measured their flatness and found that the measured flatness is acceptable for the test experiment. A pin hole X-ray source is also preparing for a laboratory experiment in order to demonstrate a X-ray interference. We investigated a possible observation of accretion disks around BHs and nearby stars. With a reasonable size of the base line, we can measure their size and possibly we can obtain an evidence of a black hole shadow.

DOI： 10.1117/12.926058

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DOI： 10.1063/1.3696189

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DOI： 10.1063/1.3696209

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We report a study of a new X-ray interferometer with a beam splitter for future observation of celestial objects. A possible configuration of an interferometer is proposed. By using a beam splitter, the length of the interferometer becomes short and without a formation flight of satellites a reasonable X-ray interferometric observation can be possible. An observation of early type stars is discussed. A laboratory experiment for performance verification is also discussed.

DOI： 10.1117/12.894244

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We report on the results of a Suzaku observation of the anomalous X-ray pulsar (AXP) IE 1841-045 at the center of the supernova remnant Kes 73. We confirmed that the energy-dependent spectral models obtained by previous separate observations were also satisfied over a wide energy range from 0.4 to similar to 70 keV, simultaneously. Here, the models below similar to 10 keV were a combination of blackbody (BB) and power-law (PL) functions, or of two BBs with different temperatures at 0.6-7.0 keV (Morii et al. 2003. PASJ, 55, L45), and that above similar to 20 keV was a PL function (Kuiper et al. 2004, ApJ, 613, 1173). The combination BB + PL + PL was found to best represent the phase-averaged spectrum. Phase-resolved spectroscopy indicated the existence of two emission regions, one with a thermal and the other with a non-thermal nature. The combination BB + BB + PL was also found to represent the phase-averaged spectrum well. However, we found that this model is physically unacceptable due to an excessively large area of the emission region of the blackbody. Nonetheless, we found that the temperatures and radii of the two blackbody components showed moderate correlations in the phase-resolved spectra. The fact that the same correlations have been observed between the phase-averaged spectra of various magnetars (Nakagawa et al. 2009, PASJ, 61, 109) suggests that a self-similar function can approximate the intrinsic energy spectra of magnetars below similar to 10 keV.

DOI： 10.1093/pasj/62.5.1249

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The Soft X-ray Spectrometer (SXS) is a cryogenic high resolution X-ray spectrometer onboard the X-ray astronomy satellite Astro-H which will be launched in 2014. The detector array is cooled down to 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from the room temperature to the ADR heat-sink is composed of superfluid liquid He, a Joule-Thomson cryocooler, and double-stage Stirling cryocoolers. It is designed to keep 301 of liquid He for more than 5 years in the normal case, and longer than 3 years even if one of the cryocoolers fails. Cryogen-free operation is also possible in the normal case. It is fully redundant from the room temperature to the ADR heat-sink. (c) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.cryogenics.2010.02.004

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Aerospace Exploration Agency (JAXA)  

The 3rd Suzaku international Conference "Energetic Cosmos : from Suzaku to ASTRO-H" (June 29-July 2, 2009. Grand Park Otaru Hotel), Otaru, Hokkaido JapanWe have developed the X-ray CCD camera system for the Soft X-ray Imager (SXI) which will be launched as focal plane detectors of X-ray telescope onboard the Japanese 6th X-ray astronomical satellite, Astro-H. The X-ray CCD is back-illuminated (BI) CCD which has an Optical Blocking Layer (OBL) directly coating its X-ray illumination surface with Aluminum-Polyimide-Aluminum instead of Optical Blocking Filter (OBF). The X-ray CCD is affected by large doses of extreme ultraviolet (EUV) radiation from Earth sun-lit atmosphere (airglow) in orbit. To evaluate the performance of polyimide that cut off EUV, we measured the EUV transmission of both OBL and OBF at various energy range between 15 - 72 eV by utilizing beam line located at the Photon Factory in High Energy Accelerator Research Organization (KEK-PF) in this March and June, and obtained the EUV transmission to be 3% at 41 eV which is as same as expected transmission from the designed thickness of polyimide layer.Meeting sponsors: The University of Tokyo, The Institute of Physical and Chemical Research, The Japan Society for the Promotion of ScienceNumber of authors: 22

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Aerospace Exploration Agency (JAXA)  

The 3rd Suzaku international Conference "Energetic Cosmos : from Suzaku to ASTRO-H" (June 29-July 2, 2009. Grand Park Otaru Hotel), Otaru, Hokkaido JapanWe report the XIS calibration on the data taken with the 2 x 2 mode and window option and the current status of the XIS Non-X-ray Background (NXB) database. The 2 x 2 mode and window option are useful for bright source observations to avoid telemetry saturation and event pile-up. The NXB database provides the best-estimated NXB spectrum for any specific observations obtained with the standard mode (Normal-Clock with no Window or Burst and 5 x 5(sub -) (3 x 3(sub -) Editing mode). The data taken with the 2 x 2 mode in the "SCI-off" era are fully calibrated, and there is no practical difference from those taken with the standard mode. A calibration study for the data taken with the 2 x 2 mode in the "SCI-on" era is on-going. The calibration for the data taken with the window option was significantly improved in the HEASOFT 6.6.2 released at 2009 April 1st. In the comparison with the standard-mode data, the gain difference around 6 keV becomes less than 10 and 15 eV in XIS 0,3 and XIS 1, respectively. We have been updating the NXB database every half a year. There is no drastic change in the light curves, but steady approximately 4 % year(sup -1) level increase and decrease are found in those of XIS 0,3 and XIS 1, respectively.Meeting sponsors: The University of Tokyo, The Institute of Physical and Chemical Research, The Japan Society for the Promotion of ScienceNumber of authors: 25

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We fabricated a novel x-ray polarimeter with a transmission multilayer and measured its performance with synchrotron radiation. A self standing multilayer with seven Mo/Si bilayers was installed with an incident angle of 45 degrees in front of a back-illuminated CCD. The multilayer can be rotated around the normal direction of the CCD keeping an incident angle of 45 degrees. This polarimeter can be easily installed along the optical axis of x-ray optics. By using the CCD as a photon counting detector with a moderate energy resolution, the polarization of photons in a designed energy band can be measured along with the image. At high photon energies, where the multilayer is transparent, the polarimeter can be used for imaging and spectroscopic observations. We confirmed a modulation factor of 45% with 45% and 17% transmission for P- and S-polarization, respectively.

DOI： 10.1063/1.3294330

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Language：English   Publishing type：Research paper (international conference proceedings)  

We report experimental results of our normal-incident EUV telescope tuned to a 13.5 nm band, with an adaptive optics. The optics consists of a spherical primary mirror and a secondary deformable mirror. A laser plasma source irradiates optical and EUV lights to the system. The system also equips a reference laser, optical light from which are nearly spherical and reflected by mirrors through the light path along the objective light. We controlled the deformable mirror to correct the wave form by referring that of the reference laser. At first, we attempted a normal AO control, where we controlled deformable mirror so that the wave form of the reference laser becomes spherical. Although we verified an improvement of angular resolution with this method, the resolution is not good enough comparing with the diffraction limit. The degradation is due to the difference between the paths of objective light and the reference laser. Then we modify the target wave form to control the deformable mirror, as the EUV image becomes best. We confirmed the validity of this control and performed a 2.1 arcsec resolution in both optical and EUV lights. © 2010 Copyright SPIE - The International Society for Optical Engineering.

DOI： 10.1117/12.863535

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

TeV J2032+4130 is the first unidentified TeV gamma-ray source discovered by HEGRA. The position is coincident with OB association Cyg OB2. Recently, the Fermi Gamma-ray Space Telescope discovered a gamma-ray pulsar in this field. Subsequent radio observation also detected the pulsation, and determined the accurate position. The TeV gamma-ray emission would be originated by the pulsar wind nebula. We observed TeV J2032+4130 with Suzaku for about 40 ksec. We discovered diffuse X-ray emission at the position of the gamma-ray pulsar.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We have developed a new back-illuminated (BI) CCD which has an Optical Blocking Layer (OBL) directly coating its X-ray illumination surface with Aluminum-Polyimide-Aluminum instead of Optical Blocking Filter (OBF). OBL is composed of a thin polyimide layer sandwiched by two Al layers. Polyimide and Al has a capability to cut EUV and optical light, respectively. The X-ray CCD is affected by large doses of extreme ultraviolet (EUV) radiation from Earth sun-lit atmosphere (airglow) in orbit as well as the optical light.In order to evaluate the performance of the EUV-attenuating polyimide of the OBL, we measured the EUV transmission of both the OBL and the OBF at energies between 15-72 eV by utilizing a beam line located at the Photon Factory in High Energy Accelerator Research Organization (KEK-PF). We obtained the EUV transmission to be 3% at 41 eV which is the same as the expected transmission from the designed thickness of the polyimide layer. We also found no significant change of the EUV transmission of polyimide over the nine month interval spanned by out two experiments.We also measured the optical transmission of the OBL at wavelengths between 500-900 angstrom to evaluate the performance of the Al that attenuates optical light, and found the optical transmission to be less than 4x10(-5).

DOI： 10.1117/12.856767

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DOI： 10.1117/12.856778

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

The Soft X-ray Spectrometer (SXS) is a cryogenic high resolution X-ray spectrometer onboard the X-ray astronomy satellite ASTRO-H. The detector array is cooled down to 50 mK using a 3-stage adiabatic demagnetization refrigerator (ADR). The cooling chain from room temperature to the ADR heat-sink is composed of superfluid liquid He, a He-4 Joule-Thomson cryocooler, and 2-stage Stirling cryocoolers. It is designed to keep 30 L of liquid He for more than 3 years in the nominal case. It is also designed with redundant subsystems throughout from room temperature to the ADR heat-sink, to alleviate failure of a single cryocooler or loss of liquid He.

DOI： 10.1117/12.856909

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We present the Suzaku results of eta Carinae in the 5-50 keV range conducted twice around the apastron in 2005 August for 50 ks and in 2006 February for 20 ks. The X-ray Imaging Spectrometer (XIS) produced hard (5-12 keV) band spectra, resolving K shell lines from highly ionized Fe and Ni. The Hard X-ray Detector yielded a significant detection in the super-hard (15-50 keV) band, which was uncontaminated by near-by sources. We constrained the temperature of the optically thin thermal plasma emission dominant in the hard band to be 3-4 keV using the K-shell line features with the XIS. We found significant excess emission above the thermal emission in the super-hard band with the PIN, confirming the previous INTEGRAL ISGRI report. The entire 5-50 keV spectra were fitted by a combination of a thermal plasma model plus a flat power-law, or a very hot thermal bremsstrahlung model for the excess emission. No significant change of the excess emission was found at different epochs within the systematic and statistical uncertainties, and no flare-like flux amplification was seen in the hard band, indicating that the excess emission is a steady phenomenon. We argue that the super-hard emission is attributable to the inverse Compton of stellar UV photons by non-thermal electrons or to the thermal bremsstrahlung of very hot plasma, and not to the bremsstrahlung by non-thermal electrons colliding with cold ambient matter.

DOI： 10.1093/pasj/61.4.629

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We describe the highly variable X-ray and UV emission of V458 Vul (Nova Vul 2007), observed by Swift between 1 and 422 days after outburst. Initially bright only in the UV, V458 Vul became a variable hard X-ray source due to optically thin thermal emission at kT = 0.64 keV with an X-ray band unabsorbed luminosity of 2.3 x 10(34) erg s(-1) during days 71-140. The X-ray spectrum at this time requires a low Fe abundance (0.2(-0.1)(+ 0.3) solar), consistent with a Suzaku measurement around the same time. On day 315 we find a new X-ray spectral component which can be described by a blackbody with temperature of kT = 23(-5)(+9) eV, while the previous hard X-ray component has declined by a factor of 3.8. The spectrum of this soft X-ray component resembles those typically seen in the class of supersoft sources (SSS) which suggests that the nova ejecta were starting to clear and/or that the white dwarf photosphere is shrinking to the point at which its thermal emission reaches into the X-ray band. We find a high degree of variability in the soft component with a flare rising by an order of magnitude in count rate in 0.2 days. In the following observations on days 342.4-383.6, the soft component was not seen, only to emerge again on day 397. The hard component continued to evolve, and we found an anticorrelation between the hard X-ray emission and the UV emission, yielding a Spearman rank probability of 97%. After day 397, the hard component was still present, was variable, and continued to fade at an extremely slow rate but could not be analyzed owing to pile-up contamination from the bright SSS component.

DOI： 10.1088/0004-6256/137/5/4160

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We report the detection of superhard (&gt; 10 keV) X-ray emission extending up to 70 keV from the classical nova V2491 Cygni using the Suzaku observatory. We conducted two similar to 20 ks target-of-opportunity observations 9 and 29 days after the outburst on 2008 April 11, yielding wide energy range spectra by combining the X-ray Imaging Spectrometer and the Hard X-ray Detector. On day 9, a spectrum was obtained at 1.0-70 keV with the Fe xxv K alpha line feature and a very flat continuum, which is explained by thermal plasma with a 3 keV temperature and power-law emission with a photon index of 0.1 attenuated by a heavy extinction of 1.4 x 10(23) cm(-2). The 15-70 keV luminosity at 10.5 kpc is 6 x 10(35) erg s(-1). The superhard emission was not present on day 29. This is the highest energy at which X-rays have been detected from a classical nova. We argue a nonthermal origin for the emission, which suggests the presence of accelerated charged particles in the nova explosion.

DOI： 10.1088/0004-637X/697/1/L54

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We have searched for pulsation of the anomalous X-ray pulsar (AXP) 4U 0142+61 in the K' band (lambda(eff) = 2.11 mu m) using the fast-readout mode of Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. We found no significant signal at the pulse frequency expected by the precise ephemeris based on an X-ray monitoring observation with RXTE. Nonetheless, we obtained the best upper limit of 17% (90% C.L.) for the root-means-quare pulse fraction in the K' band. Combined with the i' band pulsation (Dhillon et a]. 2005, MNRAS, 363, 609), the slope of the pulsed component (F-nu alpha nu(alpha) in units of Jy) was constrained to alpha &gt; -0.87 (90% C.L.) for an interstellar extinction of A(V) = 3.5.

DOI： 10.1093/pasj/61.1.51

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

We report an experimental result of our normal-incident EUV telescope tuned to a 13.5 nm band, with an adaptive optics. The optics consists of a spherical primary mirror and a secondary mirror. Both are coated by Mo/Si multilayer. The diameter of the primary and the secondary mirrors are 80 mm and 55mm, respectively. The secondary mirror is a deformable mirror with 31 bimorph-piezo electrodes. The EUV from a laser plasma source was exposed to a Ni mesh with 31 micro-m wires. The image of this mesh was obtained by a backilluminated CCD. The reference wave was made by an optical laser source with 1 μm pin-hole. We measure the wave form of this reference wave and control the secondary mirror to get a good EUV image. Since the paths of EUV and the optical light for the reference were different from each other, we modify the target wave from to control the deformable mirror, as the EUV image is best. The higher order Zernike components of the target wave form, as well as the tilts and focus components, were added to the reference wave form made by simply calculated. We confirmed the validity of this control and performed a 2.1 arc-sec resolution.

DOI： 10.1117/12.824122

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Language：English   Publishing type：Research paper (international conference proceedings)  

We developed an EUV polarimeter consisting of a transmission multilayer and a back-illumination CCD. The transmission of the multilayer at an incident angle of45-deg depends on the polarization angle. We developed a polarimeter by using the transmission. Advantages of usage a transmission multilayer are as follows. 1) The mechanics is simple, because we do not need to move the detectors. 2) High energy photons, where the multilayer is transparent, can be measured as a normal observation, if we use a CCD as a photon counting. 3) By removing the multilayer from the optical axis, normal observation with a CCD can be performed. A stand alone multilayer of Mo/Si was fabricated, which consists of seven layer-pairs with a thickness of 20 nm. We evaluated the performance of the polarimeter using a synchrotron beam line. We confirmed a modulation factor of 47% around 95 eV. © 2009 Copyright SPIE - The International Society for Optical Engineering.

DOI： 10.1117/12.825074

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We conducted a target of opportunity X-ray observation of the classical nova V458 Vulpeculae 88 d after the explosion using the Suzaku satellite. With a similar to 20 ks exposure, the X-ray Imaging Spectrometer detected X-ray emission significantly harder than typical super-soft Source emission. The X-ray spectrum shows K alpha lines from N, Ne, Mg, Si, and S, and L-series emission from Fe in highly ionized states. The spectrum can be described by a single-temperature (similar to 0.64 keV) thin thermal plasma model in collisional equilibrium with a hydrogen-equivalent extinction column density of similar to 3 x 10(21) cm(-2), a flux of similar to 10(-12) erg s(-1) cm(-2), and a luminosity of similar to 6 x 10(34) erg s(-1) in the 0.3-3.0 keV band at an assumed distance of 13 kpc. We found a hint of an enhancement of N and deficiencies of O and Fe relative to other metals. The observed X-ray properties can be interpreted as the emission arising from shocks of ejecta from an ONe-type nova.

DOI： 10.1093/pasj/61.sp1.S69

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The Soft X-ray Spectrometer (SXS) onboard the NeXT (New exploration X-ray Telescope) is an X-ray spectrometer utilizing an X-ray microcalorimeter array. Combined with the soft X-ray telescope of 6 m focal length, the instrument will have a ∼ 290cm2 effective at 6.7 keV. With the large effective area and the energy resolution as good as 6 eV (FWHM), the instrument is very suited for the high-resolution spectroscopy of iron K emission line. One of the major scientific objectives of SXS is to determine turbulent and/or macroscopic motions of the hot gas in clusters of galaxies of up to z ∼ 1. The instruments will use 6 × 6 or 8 × 8 format microcalorimeter array which is similar to that of Suzaku XRS. The detector will be cooled to a cryogenic temperature of 50 mK by multi-stage cooling system consisting of adiabatic demagnetization refrigerator, super fluid He, a 3He Joule Thomson cooler, and double-stage Stirling cycle cooler.

DOI： 10.1117/12.787952

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

The black-hole binary Cygnus X-1 was observed for 17 ks with the Suzaku X-ray observatory in 2005 October, while it was in a low/hard state with a 0.7-300 keV luminosity of 4.6 x 10(37) ergs(-1). The XIS and HXD spectra, spanning 0.7-400 keV, were reproduced successfully, incorporating a cool accretion disk and a hot Comptonizing corona. The corona is characterized by an electron temperature of similar to 100 keV, and two optical depths of similar to 0.4 and similar to 1.5, which account for the softer and harder continua, respectively. The disk has an innermost temperature of similar to 0.2keV, and is thought to protrude half way into the corona. The disk not only provides seed photons to the Compton cloud, but also produces a soft spectral excess, a mild reflection hump, and a weakly broadened iron line. A comparison with the Suzaku data on GRO J1655-40 reveals several interesting spectral differences, which can mostly be attributed to inclination effects, assuming that the disk has a flat geometry while the corona is grossly spherical. An intensity-sorted spectroscopy indicates that the continuum becomes less Comptonized when the source flares up on time scales of 1-200 s, while the underlying disk remains unchanged.

DOI： 10.1093/pasj/60.3.585

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We present the results of a Suzaku spectroscopic study of soft extended X-ray emission in the H II region of M17. The spectrum of the extended emission was obtained with a high signal-to-noise ratio in a spatially resolved manner using the X-ray Imaging Spectrometer (XIS). We established that contamination by unresolved point sources, the Galactic Ridge X-ray emission, the cosmic X-ray background, and the local hot bubble emission is negligible in the background-subtracted XIS spectrum of the diffuse emission. Half a dozen emission lines were clearly resolved for the first time, including Kα lines of highly ionized O, Ne, and Mg as well as L-series complex of Fe at 0.51.5 keV. Based on diagnosis of these lines, we obtained the following results: (1) the extended emission is an optically thin thermal plasma, represented well by a single temperature of ∼ 3.0 ± 0.4MK, (2) the abundances of elements with emission lines in the diffuse spectrum are 0.1-0.3 solar, while those of bright discrete sources are 0.3-1.5 solar, (3) the metal abundances relative to each other in the diffuse emission are consistent with solar, except for a Ne enhancement of a factor of ∼ 2, (4) both the plasma temperature and the chemical composition of the diffuse emission show no spatial variation across the studied spatial scale of ∼ 5 pc. © 2008. Astronomical Society of Japan.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We report on the detection of a transient X-ray source toward the Small Magellanic Cloud (SMC) using the X-ray Imaging Spectrometer (XIS) on board the Suzaku telescope. The source was detected at the edge of the XIS image during a routine observation of the calibration source 1E0102.2-7219, a supernova remnant in the SMC. We constrained the source position using ray-tracing simulations. No such transient source was found at the position in the other Suzaku observations, nor in all of the available archived images of other X-ray missions for the last similar to 28 years. The XIS spectrum can be explained by a single blackbody with a temperature of similar to 72 eV, and an interstellar extinction of similar to 4.9 x 10(20) H atoms cm(-2), consistent with the value to the SMC. An additional absorption edge at similar to 0.74 keV was also confirmed, which is presumably due to absorption by helium-like oxygen ions. Assuming that the source is at the distance of the SMC, the X-ray luminosity in the 0.2-2.0 keV band is similar to 10(37) erg s(-1) and the radius of the source is similar to 10(8) cm. The XIS light curve shows about a two-fold decline in X-ray flux during the 24 ks observation. Together with the archived data, the X-ray flux in the burst is at least three-orders of magnitude brighter than the undetected quiescent level. All of these properties are often seen among supersoft sources (SSSs). We conclude that the transient source is another example of SSS in the SMC.

DOI： 10.1093/pasj/60.sp1.S231

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Language：English   Publishing type：Research paper (international conference proceedings)  

We report the results of spectral analysis for black hole binary Cyg X-1, especially focussed on intensity dips. We used data otained with RXTE from May 5, 2000 for one orbital cycle, and in that time, many intensity dips are found. The dip spectrum are reduced by ∼ 2 % from non-dip spectrum even in the 20-150 keV. We fitted dip and non-dip spectra with two CompPS model, which expresses thermal comptonizaiton of emission from accretion disk by hot electron cloud with defferent optical depth. During dip, column density for softer component is significantly larger than that for harder one, which suggests intensity dip is caused by absorption of softer component. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.

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Anomalous X-ray pulsars (AXPs) are thought to be magnetars, which are neutron stars with ultra strong magnetic field of 1014-10 15G. Their energy spectra below ∼10keV are modeled well by two components consisting of a blackbody (BB) (∼0.4keV) and rather steep power-law (POW) function (photon index ∼2-4). Kuiper et al. (2004) discovered hard X-ray component above ∼10keV from some AXPs. Here, we present the Suzaku observation of the AXP 1E 1841-045 at the center of supernova remnant Kes 73. By this observation, we could analyze the spectrum from 0.4 to 50 keV at the same time. Then, we could test whether the spectral model above was valid or not in this wide energy range. We found that there were residual in the spectral fits when fit by the model of BB + POW. Fits were improved by adding another BB or POW component. But the meaning of each component became ambiguous in the phase-resolved spectroscopy. Alternatively we found that NPEX model fit well for both phase-averaged spectrum and phase-resolved spectra. In this case, the photon indices were constant during all phase, and spectral variation seemed to be very clear. This fact suggests somewhat fundamental meaning for the emission from magnetars. © 2008 American Institute of Physics.

DOI： 10.1063/1.2900159

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Publishing type：Research paper (scientific journal)  

The SXS (Soft X-ray Spectrometer) onboard the coming Japanese X-ray satellite NeXT (New Exploration Xray Telescope) and the SXC (Spectrum-RG X-ray Calorimeter) in Spectrum-RG mission are microcalorimeter array spectrometers which will achieve high spectral resolution of ~ 6 eV in 0.3-10.0 keV energy band. These spectrometers are well-suited to address key problems in high-energy astrophysics. To achieve these high spectral sensitivities, these detectors require to be operated under 50 mK by using very efficient cooling systems including adiabatic demagnetization refrigerator (ADR). For both missions, we propose a two-stage series ADR as a cooling system below 1 K, in which two units of ADR consists of magnetic cooling material, a superconducting magnet, and a heat switch are operated step by step. Three designs of the ADR are proposed for SXS/SXC. In all three designs, ADR can attain the required hold time of 23 hours at 50 mK and cooling power of 0.4μW with a low magnetic fields (1.5/1.5 Tesla or 2.0/3.0 Tesla) in a small configuration (180 mmφ× 319 mm in length). We also fabricated a new portable refrigerator for a technology investigation of two-stage ADR. Two units of ADR have been installed at the bottom of liquid He tank. By using this dewar, important technologies such as an operation of two-stage cooling cycle, tight temperature control less than 1 μK (in rms) stability, a magnetic shielding, saltpills, and gas-gap heat switches are evaluated.

DOI： 10.1117/12.788634

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Language：English   Publishing type：Research paper (international conference proceedings)  

We are developing a normal incident EUV-telescope for a future space experiment, using an adaptive optics. The primary mirror and the secondary mirror were coated with Mo/Si multi-layers. The secondary mirror is a deformable mirror. The reference wave is produced with a 1 micro-m pin hole laser and its wave front shape is used for a correction of the EUV wave shape. The imaging experiments with optical was performed with the adaptive optics system. The imaging with 13.5nm EUV was also performed but without the adaptive optics system. The optical image is almost diffraction limited. A ray trace simulation was performed and a correction method in our system, where the EUV wave form is corrected using the optical reference lights, was investigated.

DOI： 10.1117/12.787740

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SN 1006 is one of the supernova remnants (SNRs) with relatively low-temperature electrons, considering the young age of just 1000 years. We carried out SN 1006 mapping observations with the X-ray Imaging Spectrometers (XIS) and the Hard X-ray Detector (HXD) onboard Suzaku, the fifth Japanese X-ray satellite. Thanks to the excellent spectral resolution of XIS in the soft X-ray band, H-like and He-like oxygen emission lines were clearly detected, and we could make a map of the line intensity, and as well as a flux and the photon index of nonthermal component. We found that these parameters have spatial dependences from region to region in the SNR; the north region is bright in nonthermal, while dim in thermal; the east region is bright in both nonthermal and thermal; the inner region shows dim nonthermal and bright thermal emission. The photon index is the smallest in the north region. © 2007.

DOI： 10.1016/j.asr.2007.03.055

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Other Link： http://orcid.org/0000-0003-3529-3029

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The transient X-ray binary pulsar A0535+262 was observed with Suzaku on 2005 September 14 when the source was in the declining phase of the August-September minor outburst. The similar to 103 s X-ray pulse profile was strongly energy dependent, with a double-peaked profile in the soft X-ray energy band (&lt; 3 keV) and a single-peaked smooth profile in hard X-rays. The width of the primary dip is found to increase with energy. The broadband energy spectrum of the pulsar is well described with a negative and positive power law with exponential (NPEX) continuum model, along with a blackbody component for soft excess. A weak iron K alpha emission line with an equivalent width similar to 25 eV was detected in the source spectrum. The blackbody component is found to be pulsating over the pulse phase, implying that the accretion column and/or the inner edge of the accretion disk may be the possible emission site of the soft excess in A0535+262. The higher value of the column density is believed to be the cause of the secondary dip in the soft X-ray energy band. The iron line equivalent width is found to be constant (within errors) over the pulse phase. However, a sinusoidal type of flux variation of the iron emission line, in phase with the hard X-ray flux, suggests that the inner accretion disk is the possible emission region of the iron fluorescence line.

DOI： 10.1086/523295

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Language：English   Publishing type：Research paper (international conference proceedings)  

The X-ray Imaging Spectrometers (XIS) on-board Suzaku is an X-ray CCD camera system that has features of low background, good energy resolution, and high quantum efficiency (QE) at 0.2-12 keV band. However, an unexpected degradation of the QE at low energies (< 1 keV) has emerged since November 2005. Some contaminants are considered to be adsorbed on the Optical Blocking Filter (OBF) for each sensor and cause the degradation. A suspected contamination source is rubber used in the shock absorber of the satellite gyro. For the recovery of the QE, we now design to remove the contaminants by increasing the OBF temperature. Before the on-board bakeout is performed, we need to confirm on the ground that it does not cause a serious damage to the OBF. In order to reproduce the on-board contamination, we adsorbed the contaminant of ∼ 160 μg cm-2 from the rubber on a spare OBF and a Thermoelectric Quartz Crystal Microbalance simultaneously, which are cooled down to -40 °C. Although unexpected wrinkles appeared on the OBF surface during the adsorption and they remained through the subsequent bakeout, we could not find any tears on it. In addition, we estimated the desorption rate at -15 °C to be ∼ 5 μg cm-2 per day. In our presentation, we also discuss the expected effect by the on-board bakeout based on these results.

DOI： 10.1117/12.732293

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Publishing type：Research paper (international conference proceedings)  

We are developing a normal incident X-ray telescope with an adaptive optics system in order to achieve an unprecedented high-angular-resolution. The primary mirror with a diameter of 80mm is a spherical shape with a focal length of 2000 mm, which was coated by Mo/Si multilayer. The secondary mirror is a deformable mirror with 55 mm diameter, which was also coated by Mo/Si multilayer. Optical lights from a pin-hole were measured by a wave-front sensor and used as a reference for a correction of the deformable mirror. All the components were installed in a vacuum chamber. A closed loop control with the wave front sensor and the deformable mirror was successfully performed in the telescope and we confirmed the correction of the wave front. The rms-deviation of a performed wave front from a target shape during the control was ∼30 nm-rms, whereas it without control was more than ∼80 nm-rms. A 13.5 nm X-ray from an electron impact X-ray source was imaged on a backside CCD installed on a focal plane. A mesh made by steel was installed in front of the X-ray source, whose pitch and wire-thickness are 500 micro-m and 50 micro-m. The image of this mesh by optical lights from the X-ray generator is detected by the CCD. The current image quality is ∼2.4 arc-sec and this was comparable to a diffraction limit of an optical wave length with our 80mm primary mirror.

DOI： 10.1117/12.733655

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Language：English   Publisher：Progress of Theoretical Physics  

Orbital calibrations of the XIS, in terms of the energy scale, energy resolution, and quantum efficiency, are needed not only to confirm the calibrations on the ground but also to examine inevitable performance change in orbit. Fundamentals of the XIS calibration issues have been established and are implemented the softwares and the data base for general observers. We overview the current status of the XIS calibration in orbit.

DOI： 10.1143/PTPS.169.316

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10886569

Publishing type：Research paper (international conference proceedings)  

SN 1006 is the milestone of understanding the acceleration mechanism of cosmic rays, and this year is the millennium year for the remnant. We carried out SN 1006 mapping observations with the X-ray Imaging Spectrometers (XIS) onboard Suzaku satellite. Thanks to the excellent spectral response of XIS, K emission lines from highly ionized oxygen were clearly resolved. The intensity maps of these lines have been made additional to the intensity and photon index maps of the nonthermal component. We discovered that regions with strong and hard nonthermal component has weak thermal emission. The north rim of the SNR has the hardest nonthermal component. These facts might have information of efficient cosmic ray acceleration and background plasma.

DOI： 10.1143/PTPS.169.142

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DOI： 10.1016/j.asr.2007.02.020

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Other Link： http://orcid.org/0000-0003-3529-3029

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

Orbital calibrations of the XIS, in terms of the energy scale, energy resolution, and quantum efficiency, are needed not only to confirm the calibrations on the ground but also to examine inevitable performance change in orbit. Fundamentals of the XIS calibration issues have been established and are implemented the softwares and the data base for general observers. We overview the current status of the XIS calibration in orbit.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

The XIS is an X-ray Imaging Spectrometer system, consisting of state-of-the-art charge-coupled devices (CCDs) optimized for X-ray detection, camera bodies, and control electronics. Four sets of XIS sensors are placed at the focal planes of the grazing-incidence, nested thin-foil mirrors (XRT: X-Ray Telescope) orboard the Suzaku satellite. Three of the XIS sensors have front-illuminated CCDs, while the other has a back-illuminated CCD. Coupled with the XRT, the energy range of 0.2-12 keV with energy resolution of 130 eV at 5.9 keV, and a field of view of 18' x 18' are realized. Since the Suzaku launch on 2005 July 10, the XIS has been functioning well.

DOI： 10.1093/pasj/59.sp1.S23

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We studied extended X-ray emission from the Carina Nebula taken with the Suzaku CCD camera XIS on 2005 August 29. The X-ray morphology, plasma temperature, and absorption to the plasma are consistent with the earlier Einstein results. The Suzaku spectra newly revealed emission lines from various species, including oxygen, but not from nitrogen. This result restricts the N/O ratio to be significantly low, compared with evolved massive stellar winds, suggesting that the diffuse emission originated in an old supernova remnant or a super shell produced by multiple supernova remnants. The X-ray spectra from the north and south of eta Car showed distinct differences between 0.3-2 keV. The south spectrum shows strong L-shell lines of iron ions and K-shell lines of silicon ions, while the north spectrum shows them weak in intensity. This means that the silicon and iron abundances are a factor of 2-4 higher in the south region than in the north region. The abundance variation may be produced by an SNR ejecta, or related to dust formation around the star-forming core.

DOI： 10.1093/pasj/59.sp1.S151

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press  

We analyzed the X-ray emission-line profiles of three early-type stars (ζ Pup, δ Ori, and τ Sco) obtained with Chandra. A phenomenological model, where X-ray sources are distributing in wind above some lower limit radius, can fit the line profiles of ζ Pup and δ Ori
however, the fitting requires a much smaller absorption than expected from the mass-loss rate. This suggests that, if this phenomenological model represents the real X-ray emission region, there is substantial ionization or clumping of the stellar wind. The parameters derived from the line profile of τ Sco indicate that the X-ray-emitting plasma is concentrated on the stellar surface, suggesting the existence of a confined plasma on the stellar surface. © 2007. Astronomical Society of Japan.

DOI： 10.1093/pasj/59.1.237

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.

DOI： 10.1093/pasj/59.sp1.S1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV CHICAGO PRESS  

The binary X-ray pulsar A0535 + 262 was observed with the Suzaku X-ray observatory on 2005 September 14 for a net exposure of 22 ks. The source was in the declining phase of a minor outburst, exhibiting 3-50 keV luminosity of similar to 3.7 x 10(35) ergs s(-1) at an assumed distance of 2 kpc. In spite of the very low source intensity ( about 30 mcrab at 20 keV), its electron cyclotron resonance was detected clearly with the Suzaku Hard X-Ray Detector, in absorption at about 45 keV. The resonance energy is found to be essentially the same as that measured when the source is almost 2 orders of magnitude more luminous. These results are compared with the luminosity-dependent changes in the cyclotron resonance energy, observed from 4U 0115 + 63 and X0331 + 53.

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Publishing type：Research paper (international conference proceedings)  

We report the current status of the "X-mas" (X-ray milli-arcsecond) project. X-mas is an application of the AO technology to the X-ray optics, aiming to obtain high-resolution defraction-limited X-ray images. Our X-ray telescope employs the Newton optics with a paraboloid primary and a 31-element deformable secondary mirrors. The aperture of the primary mirror is 80 millimeters with the focal length of 2 meters. Multi-layer coating of the mirrors by silicon and molybdenum realizes a large reflectivity of ∼60% for the primary and 30-50% for the secondary mirror at 13.5 nm, which enables us to construct a normal incidence optics at this wavelength. We use a laser guide source and a wave front sensor to optimize the form of the secondary deformable mirror for the purpose of offsetting the large-scale figure errors in the X-ray optics. A back-side illumination X-ray CCD detector manufactured by Hamamatsu Photonics is used for X-ray detections. We have assembled all these elements and started to accumulate data. Closed-loop AO is in operation for the laser guide source. Likely X-ray images are obtained through the telescope. The results in 2005-2006 are presented.

DOI： 10.1117/12.670937

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Other Link： http://orcid.org/0000-0003-3529-3029

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We report a new type X-ray imaging polarimeter: a multi-layer-coated CCD. When the X-rays are detected by the CCD, with the incident angle of 45 deg, through the coated multi-layer, the transmissions of the P and S polarized photons are different from each other and we can get an image with a selected position angle of the polarization.By the simulation of the transmission of the multi-layer, we designed an optimal number of the layer-pair and their thickness. The target wave length is 135 angstrom, because the Mo/Si multi-layer has a good performance in this energy range. If the dead layer of the back-side CCD is 1000 angstrom, nine layer-pairs make the largest difference between the P and S transmission.We deposited the Mo/Si multi-layer directly on a back-side CCD. The CCD was exposed to the polarized photons from synchrotron radiation with 45 deg incident angle. The detected intensity is measured as a function of the photon energy and of the rotation angle around the photon beam. The detection of the polarization is confirmed. However the measured performance is lower than expected. Some possibilities of the cause are discussed.

DOI： 10.1117/12.672637

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Language：English   Publishing type：Research paper (international conference proceedings)  

We give overview and the current status of the development of the Soft X-ray Imager (SXI) onboard the NeXT satellite. SXI is a back-illuminated supportless CCD (a combination of "back-illuminated CCD" and "supportless CCD") whose imaging area and the supportless region are 42 × 42mm2 and 30mmφ respectively. The goal of the thickness of the depletion layer is 300μm, which enables us to cover the energy range of 0.3 - 25 keV. The evaluation model 'CCD-NeXT1' with the size of 24 × 48mm2 shows no performance change due to the thinning process. The test model of P-channel CCD was confirmed to have high quantum efficiency above 10 keV with an equivalent depletion layer of 300m.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ESA PUBLICATIONS DIVISION C/O ESTEC  

The Galactic black-hole binary GRO J1655-40 was observed with Suzaku on 2005 September 22-23, for a gross time span of similar to 1 day. The source was detected over a wide and continuous energy range of 0.7-300 keV, with an intensity of similar to 50 mCrab in the 1.5 - 12 keV band. At an assumed distance of 3.2 kpc, the 0.7-300 keV luminosity is calculated to be similar to 4.4 x 10(36) ergs s(-1). The source was in a typical low/hard state, since its overall spectrum was dominated by a power-law component with a photon index of similar to 1.7. The source intensity gradually decreased by 20% during the observation, involving little spectral changes above similar to 3 keV. However, at softer energies, the amplitude of variability was somewhat enhanced. This indicates the presence of an independent soft component. The spectra in the hard energy band reveal a high-energy spectral cutoff, with an e-folding energy of similar to 200 keV which is suggested to be higher than those observed from typical black hole binaries in the low/hard state.

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Other Link： http://orcid.org/0000-0003-3529-3029

Language：English   Publishing type：Research paper (other academic)  

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Publishing type：Research paper (international conference proceedings)  

We are developing a soft x-ray telescope with an adaptive optics system for future astronomical observation with very fine angular resolution of an order of milli-arc-second. From a technical point of view, we are trying to develop a normal incident telescope with multi layers. Thus the wave length is limited to be around 13.5 nm with a band pass of roughly 1nm. Since the x-ray telescope must be installed on a satellite, a stable conditions of temperature, gravity etc, can not be expected. Therefore, we investigate to use an adaptive optics system using an optical light source attached in the telescope. In this paper, we report our present status of the development. The primary mirror is an off-axis paraboloid with 80 mm effective diameter and 2 m focal length. This mirror has been coated with Mo/Si multi-layers. The reflectivity of the 13.5 nm x rays is ranging from 35% to 55%. We use a deformable mirror for the secondary mirror, which has also been coated with Mo/Si multi-layers. This mirror consists of 31 element-bimorph-piezo electrodes. The surface roughness of the mirror is ∼6 nm rms. The reflectivity of the 13.5 nm x rays is roughly 65%. The adaptive optics system using an optical laser and a wave front sensor has been performed. We are using a shack-hartmann sensor (HASO 32) with a micro-lens array and a CCD. A pin hole with one micron diameter is used for the optical light source. The precision of the measurement of the wave front shape is a few nm. X-ray exposure test is now conducting, although the optical adaptive optics system is not yet installed. The x-ray detector is a back illumination CCD. The quantum efficiency for 13.5 nm x ray is ∼50%. The pixel size is 24 micron square. X-ray source is an electron impact source with an Al/Si alloy target. We confirmed that the x-ray intensity around 13.55 nm is bright enough for our experiment. The imaging performance is now trying to improve and the adaptive optics system will be installed in this year.

DOI： 10.1117/12.620162

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Language：English   Publishing type：Research paper (international conference proceedings)  

Astro-E2 is the fifth Japanese X-ray astronomical satellite and will be launched in 2005. The Astro-E2 X-ray Imaging Spectrometers (XISs) consist of four sets of X-ray CCD cameras. Each CCD camera has an imaging area of 1024×1024 pixels and covers a region of 18′×18′ on the sky combined with an X-ray Telescope. One XIS will utilize back-side illuminated (BI) CCDs, and the other three will be equipped with front-side illuminated (FI) CCDs. The BI CCD has a higher quantum efficiency than the FI CCD below 2 keV, while the FI CCD is more sensitive to X-rays above 5 keV than the BI CCD. Both types of the CCDs have nearly the same energy resolution (full-width at half-maximum (FWHM)=∼130eV at 6 keV). All four cameras have a charge injection capability and 55Fe calibration sources, and we can correct the change of the gain and recover the degradation of the energy resolution due to radiation damage caused by cosmic rays. The sensors are cooled to -90°C to minimize thermal noise in orbit. The low temperature is also helpful to reduce the influence of the radiation damage. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2005.01.076

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Language：English   Publishing type：Research paper (international conference proceedings)  

We give an overview, the current status and future plan of the development of the Soft X-ray Imager (SXI) onboard the NeXT (Non-thermal Energy eXploration Telescope) satellite proposed to be launched around 2010. The SXI is a back-illuminated supportless CCD (a combination of "back-illuminated CCD" and "supportless CCD") whose imaging area size and the supportless region are 42mm×42mm and 30mmφ, respectively. The goal of the depletion layer of the CCD is 300μm, which enable us to cover the X-ray energy range of 0.5-20 keV. The first test model of the supportless CCD shows no performance change due to the thinning process of the CCD. We have already started processing the evaluation model 'CCD-NeXT1', which will be completed at the end of 2004. We are also studying the camera system, the focal plane assembly including thermal electric cooler (TEC) and electronics as well as the CCD chip. © 2005 Published by Elsevier B.V.

DOI： 10.1016/j.nima.2005.01.080

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Language：English   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

We measured optical and soft X-ray transmission of Optical Blocking Filters (OBFs) for Charge Coupled Device (CCD) cameras, which will be launched as focal plane detectors of X-ray telescopes onboard the Japanese 5th X-ray astronomical satellite, Astro-E 2. The filters were made from polyimide coated with Al. The X-ray absorption fine structures (XAFSs) at the K. edges of C, N, O and K and L edges of Al were measured. The depth of the absorption edge of O was deep, compared to the other elements of polyimide. This is evidence of the oxidation of Al. The optical transmission is roughly less than 10-6 except for a peak around the wave length of 550nm. Long term change of the soft X-ray transmission was measured. No significant change of the thickness of the oxidation layer was found during half year.

DOI： 10.1117/12.505589

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Language：English   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

The X-ray time variation of GRS 1915+105 is analyzed, focusing on the phase lag properties in the class theta. An energy dependent soft lag is derived. This energy dependence can be interpreted in terms of the Comptonization of high energy photons by relatively soft electrons. A Monte Carlo simulation of the Comptonization is calculated. In this computation, photons with a power-law spectrum are scattered by soft electrons. This model can account for both the spectral properties and the time variation. With this model, the size of the electron cloud which is responsible for the Comptonization is derived to be similar to3.2 x 10(7-8) cm.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

We are developing an ultra-high precision soft X-ray telescope. The design of the telescope is a normal incident one for the 13.5 nm band using Mo/Si multilayers. Two ideas are introduced, an optical measurement system to monitor the precision of the optics system, and an adaptive optics system with a deformable mirror. Using an X-ray-optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror in order to compensate for the system distortion as a closed loop system. Here, we report the current status of this project.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

We are developing an ultra high precision Soft X-ray telescope. The design of the telescope is a normal incident one for 13.5nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the precision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an X ray-optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system distortion as a closed loop system. We confirmed that the absolute precision of the wave front sensor was less than 3 nm rms. This is also confirmed that the determination of the image center of each micro lens can be ∼1/100 of the pixel size. The precision of the deformable mirror was roughly 5 nm rms. Using the closed loop control the accuracy of the repeatability of the shape of the deformable mirror is less than 2 nm rms. The shape of the primary mirror was an off-axis paraboloide with an effective diameter of 80mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5nm was ranging from 30 to 50%. The X ray-optical separation filter was made from Zr with a thickness of ∼170 nm. The transmission of the filter for low energy X-ray was measured and was roughly 50% at 13.5nm.

DOI： 10.1117/12.505571

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Language：English   Publishing type：Research paper (other academic)  

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Major elemental mapping of lunar surface has been planned using the XRS instrument on the SELENE orbiter. Arrayed charge-coupled devices (CCD) are used due to its high energy resolution. By thermal design of the XRS with radiation cooling, CCD is kept cool enough to reduce excitation of thermal electrons and improve signal-to-noise ratio. During lunar x-ray fluorescence spectrometry, concurrent monitoring of solar x-rays as well as in situ calibration of x-ray fluorescence using a standard sample is performed for quantitative elemental analysis. Observed data are processed with on-board electronics that effectively extracts x-ray events. In one-year mission, the XRS will cover all the lunar surfaces except for polar region and map elemental composition with spatial resolution of 20km. We present instrumentation of the XRS and its current status of development, as well as showing the XRS observation plan of lunar elemental mapping. © 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0273-1177(02)00487-8

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Publishing type：Research paper (scientific journal)  

X-ray fluorescence spectrometry of a near-earth asteroid has been planned to determine major elemental composition of the asteroid surface and its regional variation from the MUSES-C orbiter, which will be launched in 2002 by the M-V vehicle. We present the characteristics of the XRS instrument and its observation plan during the mission. We numerically simulated x-ray fluorescence spectrometry of asteroid that rotates in 19-hour period and has surface geologic anomaly and we investigated achievable spatial resolution through the XRS observation during the asteroid rendezvous phase. © 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0273-1177(02)00142-4

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Language：English   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Astronomical Society of Japan  

The X-ray energy spectra and Normalized Power Spectral Densities (NPSDs) of an X-ray nova, GS 2000 + 25, were investigated. The X-ray energy spectra of the source consist of two components: a hard component, which can be represented by a power-law, and an ultra-soft component, represented by radiation from an optically-thick accretion disk (the disk component). In a model in which the power-law component is the Compton-scattered radiation, it is found that the temperature of the incident blackbody radiation to the Compton cloud decreases from 0.8 kev to 0.2 kev according to the decay of the intensity, which coincides with that of the inner accretion disk. When the source changed from the high-state to the low-state, both the photon index of the power-law component (or Compton y-parameter) and the NPSD of the hard component dramatically changed as did GS 1124-683. That is, the photon index changed from 2.2-2.6 to 1.7-1.8 and the absolute values of the NPSDs at 0.3 Hz of the hard component in the low-state became about 10-times larger than those of the hard component in the high-state. These X-ray properties were similar to those of other black-hole candidates, such as Cyg X-1, GX 339-4, and LMC X-3.

DOI： 10.1093/pasj/54.4.609

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING LTD  

With extensive monitoring data spanning over 30 years from Vela 5B, Ariel 5, Ginga, Compton Gamma Ray Observatory, Rossi X-ray Timing Explorer and BeppoSAX, we find evidence for long-term X-ray variability on time-scales similar to 190-240d from the black hole low-mass X-ray binary system GX339-4. Such variability resembles the outburst cycle of Z Cam-type dwarf novae, in which the standard disc instability model plays a crucial role. If such a model is applicable to GX 339-4, then the observed variability might be due to the irradiation of an unstable accretion disc. We show that within the framework of the X-ray irradiation model, when the accretion rate exceeds a critical value, GX 339-4 enters a 'flat-topped' high/soft state, such as seen in 1998, which we suggest corresponds to the 'standstill' state of Z Cam systems.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ASTRONOMICAL SOC PACIFIC  

We performed the evaluation of domestic X-ray CCDs and compared with XIS, onboard Chandra and ASTRO-EII. We evaluate them with analog electronics made for XIS. After fine tuning of gain, we found that the energy resolution of the CCD is about 135eV at 5.9 keV (FWHM) and the read-out noise of about 6 electron. This result shows that domestic X-ray CCDs are as good as XIS except for the read-out noise.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ASTRONOMICAL SOC PACIFIC  

We report on the development of the ISAS Ginga archive. At ISAS, all the Ginga archive and analysis software were originally developed on the main-frame computers. We are installing them to the UNIX environment with minor modification so that all the analysis will become possible in the modern network computing environment. The archive will be made public from ISAS PLAIN Center (Center for Planning and information systems) in near future.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

We present the study of the aperiodic time variation of the binary X-ray pulsar Centaurus X-3 observed with the Rossi X-Ray Timing Explorer (RXTE). We extracted light curves from six energy bands and calculated cross-spectral functions between the energy band containing the iron K lines (iron band) and the remaining bands. We discovered, for the first time, that the temporal variation of iron band emission is delayed as compared with that of the other energy X-rays by 0.39 + 0.10 ms (1 σ error) We also discovered that the time difference shows a general trend such that the higher energy X-rays are advanced in comparison with the lower energy X-rays with the exception of the iron band. Assuming that the iron emission lines are fluorescent lines in origin and are emitted by circumstellar matter, we derived 5.6 + 1.5 ms for the time delay of the temporal variation of the iron line from the average temporal variation in the energy band above the iron absorption edge, taking into account the energy spectral shape and the photoelectric absorption cross section. This result leads to a determination of (1.7 ± 0.5) × 108 cm for the distance between the original X-ray source and the reprocessor, which emits the iron lines. The general trend of the hard X-ray advance is considered to be related to the X-ray emission mechanism on the neutron star. © 2001. The American Astronomical Society. All rights reserved.

DOI： 10.1086/323848

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Soft X-ray response of X-ray Imaging Spectrometers (XIS) for the Astro-E satellite is measured with a grating spectrometer system at Osaka. First, relation between incident X-ray energy and output pulse height peak (E-PH relation) is examined with an SX grating. It is found that jump in the E-PH relation around Si-K edge is at most 2.7 eV. Second, quantum efficiency (QE) of the XIS in 0.4-2.2 keV range is measured relatively to the reference CCD of which absolute QE was calibrated with a gas proportional counter. The QE is-fitted with a model in which CCD gate structures are considered. Systematic error on the QE results is estimated by referring an independent measurement. Third, tuning and improvement of the response function is performed. We employ six components to reproduce the response profile of the XIS. In this paper, improvement of one component which is originated in the events absorbed in the channel-stop is presented.
Neverthless, Astro-E was lost due to the launch failure. We overview the XIS project in its flight model phase, modified points of the design, problems and solutions etc., in order to be utilized in a possible recovery of the satellite.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

XIS ( X-ray Imaging Spectrometers) are four sets of X-ray CCD cameras, installed on the focal plane of the X-ray telescopes of ASTRO-E satellite, which will be launched in February, 2000. We have been calibrating the low energy ( 0.25 - 2.2 keV) response of the XIS using a spectrometer system in Osaka University. In this paper, we report the results of the calibration of the XIS EM ( Engineering Model ).
We confirmed the energy resolution is about 130 eV at 5.9 keV (FWHM) and readout noise is similar to 3 - 4 electrons (rms) at -90 degrees C, And we measured the XIS response and energy resolution as a function of incident X-ray energy from 0.25 keV to 2.2 keV almost continuously, and absolute quantum efficiency.
Based on the procedure we established, we are going to calibrate the XIS FM starts from August, 1998.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

The optical and X-ray transmission of the test samples of optical blocking filters (OBF) for the XIS (Xray Imaging Spectrometer; CCD camera onboard the ASTRO-E satellite) were measured. Unexpected high transmission of optical lights was found. The oxidation of the aluminum layer is one possible cause of the high optical transmission. (C) 2000 COSPAR. Published by Elsevier Science Ltd.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON PRESS LTD  

MAXI has been approved as one of the first payloads on JEM-EF (Japanese Experiment Module Exposed Facility) on the International Space Station. It will be developed in collaboration with NASDA (NAtional Space Development Agency of Japan) to be launched in 2003. The objective of MAXI is to monitor X-ray sources over the whole sky with unprecedented sensitivity (less than 3 mCrab in 1 day). Two instruments are planned. The GSC (Gas Slit Cameras) are 1-dim position sensitive proportional counters. The SSC (Solid-state Slit Cameras) contain X-ray CCDs. The GSC covers 2-30 keV with a large window size (more than 5000cm(2)) and a low background rate. The SSC has a smaller window (similar to 200cm(2)), but has a higher energy resolution (E/Delta E similar to 50) and a sensitivity in the lower energies (0.5-10 keV). MAXI will be the first spectroscopic all-sky monitor. Objects to be observed are X-ray transients, AGNs, gamma-ray burst afterglows, CXB and so on. (C) 2000 COSPAR. Published by Elsevier Science Ltd.

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We present the key scientific objectives of remote x-ray spectrometry in Muses-C mission to a near-earth asteroid and the specification of the onboard x-ray spectrometer, XRS. The XRS will determine major elemental composition of the asteroid surface and its regional variation by observing the x-rays excited by solar x-ray irradiation. Information on surface roughness will be derived from the observations at various phase angles. In-flight calibration will be performed by observation of cosmic x-rays along the trajectory orbit of the Muses-C. In order to improve energy resolution and to extend detection energy range, charged-coupled devices are used as x-ray detectors. In situ calibration of x-ray fluorescence by solar x-ray irradiation into the onboard standard sample will improve the accuracy of quantitative elemental analysis. ©1999 COSPAR. Published by Elsevier Science Ltd.

DOI： 10.1016/S0273-1177(99)00942-4

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Proceedings of SPIE - The International Society for Optical Engineering  

Soft X-ray response of X-ray Imaging Spectrometers (XIS) for the Astro-E satellite is measured with a grating spectrometer system at Osaka. First, relation between incident X-ray energy and output pulse height peak (E-PH relation) is examined with an SX grating. It is found that jump in the E-PH relation around Si-K edge is at most 2.7 eV. Second, quantum efficiency (QE) of the XIS in 0.4-2.2 kev range is measured relatively to the reference CCD of which absolute QE was calibrated with a gas proportional counter. The QE is fitted with a model in which CCD gate structures are considered. Systematic error on the QE results is estimated by referring an independent measurement. Third, tuning and improvement of the response function is performed. We employ six components to reproduce the response profile of the XIS. In this paper, improvement of one component which is originated in the events absorbed in the channel-stop is presented. Neverthless, Astro-E was lost due to the launch failure. We overview the XIS project in its flight model phase, modified points of the design, problems and solutions etc., in order to be utilized in a possible recovery of the satellite.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We calibrate the X-ray imaging spectrometers, which are CCD cameras installed on the ASTRO-E satellite, by using dispersed continuous soft X-rays from a grating spectrometer. We obtained the signal-pulse height and energy-resolution as a function of X-ray energies continuously. However, the wings of the line spread function of the grating distorts the center of the signal-pulse height derived by a simple analysis. An estimation of this distortion is presented. We also describe two methods of extracting the pure signal-pulse-height distribution from the data using the spectrometer. A brief description of the low-energy tail is presented. (C) 1999 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We measured the optical and the X-ray transmission of the optical blocking filters for the X-ray Imaging Spectrometers (XISs) which are the X-ray CCD cameras of the ASTRO-E satellite. We conclude that the oxidation of the aluminum reduces the optical transmission down to similar to 60-70% of the theoretical value of the aluminum. We achieved optical transmission below 5 x 10(-5) in the range from 4000 to 9500 Angstrom by using aluminum thickness of 1200 Angstrom, while the theoretical calculation requires 800 Angstrom. The measurement of absolute quantum efficiency of XIS is also performed at several particular energies. We confirmed 20% quantum efficiency at 0.5 keV for the XIS engineering model (XIS EM). (C) 1999 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：E D P SCIENCES  

MAXI is an X-ray all-sky-monitor which will be on the Japanese Experiment Module of the International Space Station. Its objective is to monitor X-ray sources over the entire sky with the sensitivity of less than 3mCrab in 1 day. The GRB afterglow is one possible objective. One could expect similar to 25 afterglows to be detected a year at the early stage with this experiment.

DOI： 10.1051/aas:1999299

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Monitor of All-Sky X-ray Image(MAXI) is the first astrophysical payload for the Japanese Experiment Module (JEM) on the International Space Station (ISS). It is designed for monitoring all sky in the X-ray band. Two kinds of X-ray detectors, the Gas Slit Camera (GSC) and the Solid-state Slit Camera (SSC), are employed. The former is the gas proportional counter with one dimensional position sensitivity and the latter is the X-ray CCD. We have designed and constructed the engineering models of both detectors. We have also developed an X-ray irradiation facility in the Tsukuba Space Center (TKSC) of National Space Development Agency of Japan (NASDA). We report the status of the mission and introduce the X-ray irradiation facility.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

MAXI (Monitor of All-sky X-ray Image) is the first astrophysical payload for Japanese Experiment Module (JEM) to be designed for all sky X-ray monitoring. MAXI is a slit scanning camera which consists of two kinds of X-ray detectors; one is one-dimensional position sensitive proportional counters with total area of similar to 5000 cm(2) (here we call GSC) and the other is an X-ray CCD array with total area similar to 200 cm(2) (here we call SSC). The GSC subtends a field of view with an angular dimension of 1 degree times 180 degrees, while the SSC does a field of view with an angular dimension of 1 degree times a little less than 180 degrees. Thus, in the course of one station orbit, MAXI can scan almost all sky with a precision of 1 degree and with X-ray energy range of 0.5 - 30 keV. MAXI with a total weight of about 500 kg will be attached to JEM exposed facility in 2003.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

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Publishing type：Research paper (scientific journal)  

X-ray fluorescence spectrometry of the Moon using a CCD-based instrument 'XRS' is planned with the SELENE (Selenological and Engineering Explorer) orbiter, which will be launched in 2003. In the Apollo 15 and 16 missions, elemental mapping of Mg, Al and Si has been performed at the lunar equatorial regions for only 9% of the total surface. Much improved datasets will be obtained by using the XRS to map most of major elements, for 90% coverage of the total surface, and within 20 km spatial resolution. Key scientific objectives are (a) to measure the global average of lunar surface composition for investigation of the overall properties of lunar crust, (b) to map the rock-type distribution to study the formation and evolution of the crust and the maria, and to speculate the origin of the dichotomy, (c) to survey the chemical pattern of lava flows, or bottoms of craters or basins, for surveying the vertical structure and composition of the lunar crust and mantle. We describe the XRS instrument.

DOI： 10.1016/S0273-1177(99)00547-5

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Language：English  

DOI： 10.1016/S0168-9002(99)00601-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

We observed Her X-1 using the Ginga observatory in the spring of 1989 with the primary intention of studying the evolution of the pulse profile through the course of the 35 day X-ray HIGH-LOW cycle in that source. These observations cover 16 separate days in two MAIN HIGH states and in the intervening SHORT HIGH state. We have augmented these data with four additional Ginga observations of Her X-1 taken for other purposes but useful for our study. We present light curves in the 1-37 keV energy band for the seven high states covered by these data together with a representative sample of pulse profiles. The signal-to-noise ratio for these profiles is generally excellent, and collectively they provide a sound base for studying the evolution of the pulse profile. Of particular utility is the 1989 May observation, which for the first time provides extensive coverage of a short high state at high photon counting rate. By combining pulse phase and frequency information from all three high state observations in 1989, we are able to determine the phase alignment of main high and short high pulse profiles with high confidence. We identify components in the Her X-1 pulse profile by their distinctive spectral signatures, and we establish the existence of a definite, repetitive pattern of pulse shape variations tied to the 35 day high-low cycle. Comparing pre-Ginga observations of pulse profiles superposed according to the 35 day phase indicates that this pattern has persisted over the past two decades. Moreover, the pulse phase alignment of the 1989 data allows the identification of components common to the main high and short high pulse profiles. One of the key elements of this pattern is the rapid change in pulse profile that occurs roughly 7 days into each main high state. In examining possible mechanisms for this interval of accelerated evolution, we are led to consider a class of models that involve dynamical changes in accretion flow geometry arising from neutron star obliquity. These models, however, suggest asymmetries in the X-ray illumination of the companion star that may conflict with extensive optical observations of the Her X-1 system. By contrast, kinematic changes in the geometrical aspect of obscuring matter flows near or within the magnetosphere that are tied to accretion disk precession provide a mechanism that may be consistent with observations.

DOI： 10.1086/305910

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV CHICAGO PRESS  

A new X-ray pulsar, AX J1820.5-1434, has been discovered during the ASCA Galactic plane survey project on April 9, at R.A. = 18(h)20(m)29.(s)5, decl. = -14 degrees 34'24 " (equinox 2000.0; error radius 0.'5). A coherent pulsation was detected from the source with an apparent barycentric pulse period of 152.26 +/- 0.04 s. The mean flux, not corrected for the interstellar absorption, was 2.3 x 10(-11) ergs s(-1) cm(-2) in the 2-10 keV energy band. The energy spectra obtained by the GIS and SIS can be fitted by a power-law model (photon index = 0.9 +/- 0.2) with a large column density of 9.8 +/- 1.7 x 10(22) H atoms cm(-2). These parameters indicate that the new pulsar is a highly obscured accretion-driven binary X-ray pulsar. This discovery of a faint pulsar suggests existence of many hidden pulsars in our Galaxy.

DOI： 10.1086/305291

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We present x-ray spectra obtained by a charge coupled device (CCD) from an electron impacting x-ray source using several kinds of electron targets: Au, Al-bronze, Al, and pure Al. The x rays from the source are dispersed by a grating and the dispersed x rays are focused on the CCD. Owing to the fine spatial and moderate energy resolutions of the CCD, fine spectra with 2 eV energy resolution up to 2.2 keV are obtained. X rays from the purl Al target (99.999% purity) provide good continuum x rays except for Al K x rays. This continuum source is useful as a calibration source for low energy x-ray detectors. (C) 1998 American Institute of Physics.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

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Language：English   Publisher：The Japan Society of Applied Physics  

We report the use of an improved technique to measure the X-ray detection efficiency of a charge-coupled device (CCD) with a subpixel resolution. This technique makes use of a parallel X-ray beam and metal mesh placed closely on the CCD. The mesh has many circular holes spaced at distance of 4 times the CCD pixel size (multi-pitch mesh). We could identify the interaction position of X-rays both for single events and for split pixel events. By using this method, we demonstrated how various types of X-ray events are formed inside the CCD. We have already shown that the two-pixel split events were formed near the pixel boundary. We clearly showed that the three-pixel events were formed when the interaction position was close to the pixel corner, whereas the four-pixel split events were formed when the interaction position was much closer to the pixel corner. We found that the center of gravity of split events could represent the interaction position with an uncertainty of 0.13 pixel size.

DOI： 10.1143/JJAP.37.2734

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Language：English   Publisher：The Japan Society of Applied Physics  

We report the use of a new technique to measure the X-ray detection efficiency of a charge-coupled device (CCD) with subpixel resolution. The new technique makes use of a parallel X-ray beam and metal mesh placed just in front of the CCD. The CCD camera we used is a conventional system using the TC213 (Texas Instrument Japan (TIJ)) whose pixel size is 12 &micro; m &times;12 &micro; m with one million pixels. The mesh has 4 &micro;m diameter holes spaced at 12 &micro;m intervals. We produced an efficiency map within a typical pixel showing the gate structure in detail: a virtual gate, a clock gate and an antiblooming gate. The gate structure we measured is consistent with the manufacturer's design value. By selecting single pixel events, we detected a pixel boundary. Additional plans for application will also be discussed.

DOI： 10.1143/JJAP.36.2906

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Other Link： https://jlc.jst.go.jp/DN/JALC/00046868282?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

NASDA (NAtional Space Development Agency of Japan) has selected MAXI as an early payload of the JEM (Japanese Experiment Module) Exposed Facility (EF) on the Space Station. MAXI is designed for all sky X-ray monitoring, and is the first astrophysical payload of four sets of equipment selected for JEM. MAXI will monitor the activities of about 1000-2000 X-ray sources.
In the present design, MAXI is a slit scanning camera system which consists of two kinds of X-ray detectors; one with one-dimensional position sensitive proportional counters and the other with an X-ray CCD array employed for one-dimensional imaging. MAXI will be able to detect one milli-Crab X-ray sources in a-few-day observations. The whole sky will be covered completely in every orbit of the Space Station. MAXI will be capable of monitoring variability of galactic and extragalactic sources on timescales of days with a sensitivity improvement of a factor of 5 or more over previous missions.
NASDA and RIKEN have jointly begun the design and construction of MAXI. The payload will be ready for launch in 2003.
In this paper we will present the scientific objectives of MAXI, a basic design and some simulation results, after introducing the present status of JEM.

DOI： 10.1117/12.278898

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

We show that stellar black hole X-ray binaries have two novel states: the power-law hard state and the power-law soft state, which depend not only on X-ray luminosity but also on previous history of X-ray luminosity, i.e., the states show large hysteretic behavior which is dependent upon X-ray luminosity by a factor of about 100. This large hysteresis probably cannot be explained by already existing accretion disk models. The two states are represented by two (hard and soft) types of power-law spectral components. In the rising phase of the outburst of an X-ray flare or an X-ray nova, the black hole X-ray binary is in the power-law hard state and the power-law component has a photon index (-γ) of about -1.7 (γ = 1.5-1.9) in the X-ray range of 3-40 keV. This state continues until near or just before the maximum X-ray flux (2-100 keV). The state then changes to the power-law soft state, in which the photon index (-γ) of the power-law component changes to about -2.7 (γ = 2.2-3.0) in the X-ray range of 3-40 keV. Following this change, a large multi-temperature disk blackbody component (approximately represented by blackbody radiation of kT = 0.5-1 keV) appears. This state continues until the X-ray flux has decreased to about 1/100 of its maximum. The disk blackbody component then decreases rapidly and the photon index (-γ) of the power-law component changes to about -1.7. This is the beginning of the power-law hard state. In the power-law hard state, slight traces of or no disk blackbody component is observed. The short-term variability of the power-law components and the size of the X-ray emitting regions are different in these two power-law states, implying completely different X-ray production processes. This result was derived from the combined observed results of GS 1124-683, GX 339-4, and Cyg X-1.

DOI： 10.1086/187804

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASTRONOMICAL SOC JAPAN  

We describe the orbital period change of the X-ray binary Cygnus X-3, and present three new times of X-ray minima, obtained using the Ginga and ASCA satellites. Before 1990, the long-term ephemeris of Cyg X-3 required the introduction of a second time derivative, P, of order -(1.27 +/- 0.19) x 10(-10) yr(-1) This value indicates that the first time derivative, P, changes from a positive to a negative value around 1986. However, the new ASCA data points presented here do not confirm this large P variation and indicate a significantly smaller P of -(8.13 +/- 1.15) x 10(-11) yr(-1) and a global period change of P/P = (1.17+/-0.44) x 10(-6) yr(-1). The derived P can be explained by a large mass-loss rate of 0.58 x 10(-6) M(T) yr(-1), where M(T) is the total mass of the Cyg X-3 system. This value is consistent with the expected mass-loss rate of the Wolf-Rayet star of about 10(-6)M(.) yr(-1). The existence of a red-noise type fluctuation is also described.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASTRONOMICAL SOC JAPAN  

A bright X-ray nova, GS 1124-68 (Nova Muscae 1991, GRS 1124-68), which later turned out to be a promising black-hole binary with evidence of large mass, was observed with the Large Area Counters onboard Ginga from its discovery in 1991 January to its quiescent state in 1991 September. The X-ray intensity reached a maximum (similar to 8 Crab) eight days after its discovery, then decreased exponentially with an e-folding time of about similar to 30 d. Temporary increases in the luminosity were found similar to 80 d and similar to 200 d after the outburst. The source was last detected at similar to 2 mCrab on the 239th day after the outburst; although subsequent observations were carried out on days 260 and 282, the source was below the detection limit (similar to 0.3 mCrab). GS 1124-68 exhibited such a drastic state transition that was very reminiscent of the high-low transition of black-hole candidates Cyg X-l and GX 339-4, between the 131st day (May 18) and 157th day (June 13) after the outburst. Before the transition, the energy spectrum was characterized by a thermal soft component which was dominant below similar to 8 keV, and a power-law like hard-tail component, which was significant above that energy. After the transition, the energy spectrum became much harder. The spectrum was approximately represented by a single power-law function with a photon index of similar to 1.7. Intense short time variations, which were quite similar to those in the low state of Cyg X-l, GX 339-4 and GS 2023+338, became prominent down to a timescale of milliseconds. The outburst mechanism, the origin of the soft component and the state transition can be favorably explained in terms of an optically thick accretion-disk model around a similar to 6M. black-hole at a distance of similar to 2.5 kpc.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL SCIENCE LTD  

The Japanese X-ray astronomy satellite Ginga has observed Cyg X-3 in high- and low-intensity states. The X-ray spectrum of Cyg X-3 is so variable and complex that no unified model which can well explain all the observed spectra has yet been proposed. Now we have achieved a model functional form which is well fitted to X-ray spectra in most cases. Most parameters of the present 'unified model' have been proposed in previous papers, but an essential point of this model is a successful combination of physical parameters. The model consists of three components: (1) an absorbed power-law component modified with an exponential cut-off at high energy, (2) an absorbed blackbody component and (3) an iron emission line. The model fitting results in the hydrogen column density representing the absorption for the power-law component being thinner than that for the blackbody component. In addition, the observed spectra require an absorption edge at an energy of about 9 keV. In the fitting of our model to the Ginga data, the reduced chi2 value is less than 1.35 [corresponding to the 90 per cent confidence level (dof = 29)] for 85 per cent of the spectra. We present here these parameter values in detail and consider their physical meaning.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASTRONOMICAL SOC JAPAN  

The bright Galactic bulge source GX 3+1 (4U 1744-26) was observed with the Ginga satellite on several occasions from 1987 through 1990. The source has been found to show flux variations of a factor of 2 on the time scales of years. The hardness ratio, which is a measure of the spect;al shape, stayed almost constant during the variations. Two type-I X-ray bursts were detected near to the lower end of the hu( variations. When the variabilities were investigated on a shorter time scale of days, upper and lower banana branches were found to clearly appear in the hardness-intensity diagram. The branches become smeared out if data are accumulated for much longer than a few days in the hardness-intensity diagram. As. indicated by the presence of a banana branch, the short-term variations are correlated variations between the intensity and the hardness and, hence, their nature is very different from that of the long-term variations. This means that the long- and short-term variations have different origins. If the burst detection with Hakucho and Ginga in a low state reflects a red change in the mass accretion rate, the long-term variations may be determined by changes in the mass accretion rate. This would lead to the conclusion that the change in the mass accretion rate may not be responsible for the formation of the banana branches. We also discuss another possible interpretation that the mass accretion rate determines the branches, not the long-term variations.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

The all sky monitor (ASM) on board Ginga discovered an X-ray outburst from the recurrent X-ray pulsar, X0115+634, on 1990 February 5. The maximum intensity of about 400 mcrab (1-20 keV) occurred around February 11. We have determined an intrinsic pulse period of 3.614690±0.000002 s as well as the orbital parameters. By combining the present results with previous ones obtained with other satellites, we can study the evolution of the orbital parameters. In particular, we have determined the apsidal motion of the orbit, ω̇=0°.030±0°.016 yr-1 (95% confidence). This determination places constraints on the mass-radius relation of the Be companion. An X-ray spectrum up to 60 keV was obtained with the LAC. We confirmed two absorption-line features that are cyclotron resonance lines originating from a magnetic source with field strength of 1 x 1012 G and magnetic dipole moment, μ, of 1 x 1030 G cm-3. Timing data obtained when the source was faint could not be connected with timings at a higher intensity, suggesting a change in the pulse shape. Based on our estimate of μ, the source was then near the critical accretion luminosity, Lcrit, below which a "propeller" effect becomes effective.

DOI： 10.1086/171240

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASTRONOMICAL SOC JAPAN  

We present the results of X-ray scan observations of X-ray novae during quiescence, performed with the y Large-Area Proportional Counters (LAC) onboard Ginga. The scans of GS 2000+25 were made 155d before the peak of the 1988 outburst and 382d after the peak. The derived upper limits to the X-ray luminosity in the energy range between 1.2 and 37.1 keV are (3-9)x10(33) erg s-1 for a distance of D almost-equal-to 2 kpc. For such X-ray luminosities, the mass-overflow instability of the companion star is difficult to trigger. GS 2023+338 was X-ray scanned 320d before the peak of the 1989 outburst and 442-443d after the peak. LAC found an X-ray source at a distance of approximately 0.1 arc degree from the position of GS 2023+338 after the eruption. The possibility that this source is GS 2023+338, itself cannot be discarded if its luminosity is highly variable. If this is the case, the quiescent X-ray luminosity of GS 2023+338 is of order 10(34) erg s-1 for a distance of D almost-equal-to 3 kpc, and may be sufficient to trigger a mass-overflow instability. The disk instability model is, on the other hand, viable for both stars.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASTRONOMICAL SOC JAPAN  

We detected an X-ray outburst in the Vela-Puppis region with the All Sky Monitor (ASM) aboard Ginga on 1990 November 22. Following observations by the Large Area proportional Counter (LAC) revealed that this outburst consisted of two transient sources, GS0834-430 and GS0836-429, accidentally in the same field of view of the LAC by a separation of only 0.4 degree. These two transient X-ray sources were subsequentially monitored with the LAC until 1991 May. GS 0834-430 was identified by an X-ray pulsar with a period of 12.s3. This pulsar shows a power-law energy spectrum with a photon index of approximately 0.9, and with a high-energy cutoff that is typical of X-ray pulsars. GS 0836-429 was identified by an X-ray burster, which shows typical type-I bursts approximately every 2 h.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV CHICAGO PRESS  

GX 339-4 was observed with the large area counters (LAC) onboard Ginga in its very high state, where the X-ray intensity was about a factor of 2-3 larger than its high state and it showed very rapid variations on time scales of less than several minutes, which had not been observed earlier in the high state of this source. The X-ray energy spectrum was very soft; it consisted of a low-energy component and a high-energy tail. The low-energy component could be interpreted as being due to disk blackbody radiation (the disk blackbody component) and the high-energy tail as being due to Compton-scattering radiation (the Comptonized blackbody component). The X-ray energy spectrum also showed K-edge absorption of highly ionized iron atoms of about 10(19) cm-2 and an iron emission line with an equivalent width of about 60-100 eV.
On short time scales of less than several minutes, the X-rays showed rapid time variations. For instance, in power spectral density functions, 6 Hz quasi-periodic oscillations (QPOs), very low frequency noise (VLF noise), and low-frequency noise (LF noise) were recognized. There are three types of power spectral density functions. Time variations such as dips and flip-flops were also observed. These rapid time variations are due to the Comptonized blackbody component.
On long time scales larger than hours, the disk blackbody component and the Comptonized blackbody component changed independently. However, these changes took place within some restricted regions in an X-ray hardness ratio (color)-intensity or a color-color diagrams. These are a hardness ratio increasing (with the X-ray flux) branch, a hardness ratio decreasing branch, and their crossing region. These two energy spectral branches and their crossing region have three different types of power density spectra: these different branches and regions have different time variations on time scales of less than several minutes. In the hardness ratio increasing branch, the hard Compton-scattering component is the main cause of the long-term time variation of the X-ray flux, and in the hardness ratio decreasing branch, the disk blackbody component is the main cause of the long-term time variation of the X-ray flux.
On a time lag versus Fourier period diagram, the time lag between time variations of different energy X-rays showed shoulder structures in addition to the large time lags at large Fourier periods similar to those observed in Cygnus X-1. The time variations of the X-rays of 2.3-4.6 keV were most advanced: time variations of X-rays with both lower and higher energy than 2.3-4.6 keV showed time lags relative to those of 2.3-4.6 keV X-rays. These facts together with the X-ray energy spectrum can be explained in terms of a high-energy component being due to a Compton-scattering cloud of size of about 10(9) cm, temperature kT(e) of about 30 keV, and Thomson scattering depth of about 0.5-1.0; the variable blackbody radiation with kT = approximately 1 keV is incident to the large Compton-scattering cloud.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV CHICAGO PRESS  

From a pulse-timing analysis of Ginga observations of the binary X-ray pulsar Her X-1 obtained during the interval 1989 April-June we have determined local orbital parameters for a SHORT HIGH state. We have also determined an orbital epoch in the adjacent MAIN HIGH state. By comparing these orbital solutions with previously published results, we have detected a decrease in the orbital period for Her X-1 at an average rate of P/P = (- 1.32 +/- 0.16) x 10(-8) yr-1 over the interval 1971-1989. This is substantially larger than the value predicted from current estimates of the mass transfer rate, and motivates consideration of other mechanisms of mass transfer and/or mass loss. A second result from these observations is a close agreement between orbital parameters determined separately in MAIN HIGH and SHORT HIGH states. This agreement places strong constraints on the obliquity of the stellar companion, HZ Her, if undergoing forced precession with a 35 day period. As a consequence further doubt is placed on the slaved-disk model as the underlying cause of the 35 day cycle in Her X-1.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

The highly variable X-ray luminosity of LMC X-3 is found to be strongly modulated with a period of ∼198 (or possibly ∼99) days. Observations from both Ginga and HEAO 1 satellites show this periodic variation. For energies &lt
13 keV, the X-ray intensity and hardness are positively correlated
for higher energies, there appears to be no correlation. Available optical photometry indicates the mean V brightness also varies by &gt
1 mag with this same long-term period. The regularity of this "clock" in LMC X-3 suggests that it may be related to an accretion disk precession, similar to that seen in LMC X-4, Her X-1, SS 433, or possibly periodic variations in the mass transfer rate.

DOI： 10.1086/170676

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Publishing type：Research paper (scientific journal)  

An outburst of the transient X-ray pulsar X0115+634 was detected with the All Sky Monitor (ASM) on board Ginga on 1990 February 5. Follow-up observations with the large-area proportional counters (LACs) revealed complex changes in the energy spectrum which depend on the phase of the 3.6 s pulsation. We find that characteristic structures in the spectra above 10 keV can be best interpreted as two dips at ∼12 and ∼23 keV, although not at all phases. The center energies of the two dips are consistent with the harmonic relation of 1:2, showing phase-dependent ±10% variations with pulse phase. The results strongly suggest that the structures in the spectra are due to cyclotron resonant scattering and the two apparent absorption lines are ascribed to the fundamental and second harmonics. This indicates a magnetic field strength on the neutron star surface of ∼1 × 1012 G. Equivalent widths of the second harmonic line are about 2 times larger than those of the first harmonic line, depending on the pulse phase.

DOI： 10.1086/186085

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press  

We present a three-year random sample of the X-ray flux variations of the bright Galactic Bulge source GX 5-1 obtained with the Ginga All-Sky Monitor. The data allow us, for the first time, to perform a statistical study of the branch behaviour of a Z source. They cover 98 per cent of the branch pattern displayed by the source (90 per cent confidence). The pattern remained remarkably stable over the three years of observation. The horizontal branch (HB) extends over a factor of 2 in X-ray intensity, the source spends about equal time in the HB and in the normal branch (NB), and no flaring branch is detected. The branch behaviour is random and uncorrelated on time-scales longer than several days. Consequences of these results for near-critical accretion rate models of the NB, and for the magnetic field strength of GX 5-1 relative to other Z sources are discussed.

DOI： 10.1093/mnras/248.4.751

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Publishing type：Research paper (scientific journal)  

A remarkable absorption feature at 28.5 keV, attributable to electron cyclotron resonance, has been discovered in the 1.9-60 keV X-ray spectrum of the recurrent transient X-ray pulsar X0331+53 (V0332+53). The observed resonance energy implies a neutron star surface magnetic field of 2.5(1 + z) × 1012 G, where z is the gravitational redshift. The detection was made with the Ginga observatory in 1989 October, during an outburst of this transient with a flux level of ∼ 0.3 Crab. The feature is very deep and has been resolved with excellent statistics. This is the fourth unambiguous detection of cyclotron resonant scattering features from X-ray pulsars, suggesting that these features are a common phenomenon among these objects. An empirical relation found between the cyclotron resonance energy and the spectral cutoff energy suggests that the magnetic field strengths of the known X-ray pulsars are clustered in a range (1-4) × 1012 G.

DOI： 10.1086/185888

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

The All Sky Monitor (ASM) on board the Ginga satellite discovered an X-ray nova, GS 1354-64, on 1987 February 13. An optical counterpart was identified on 1987 March 28, which had a visual magnitude of 16.92 mag at discovery. The ASM has monitored almost the entire light curve from the rising phase until it reached the detection limit during the decay. The maximum flux was about (2.9±0.1) × 10-9 ergs s-1 cm-2 in the 1-10 keV band. The decay time constant was about 66 days, assuming an exponential decay. The energy spectrum is well-described by an ultrasoft component with a disk blackbody spectrum, with inner disk temperature of 0.7 keV and radius of 51(cos i)-0.5(D/10 kpc) km, where i is the inclination of the disk and D is the distance to GS 1354-64, plus a hard tail with a power-law shape (photon index = 2.1). Softening of the spectrum during the decay phase was observed, which may be attributed to a temperature decrease of the X-ray emission region or to a decrease of the intervening absorption column density. The position of thel source is consistent with the positions of both MX 1353-64 and Cen X-2. However, the characteristics of GS 1354-64 were markedly different from either of these sources.

DOI： 10.1086/169222

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ALTHOUGH neutron stars are generally believed to be born with intense (1011-1013 G) magnetic fields1,2, which then gradually decay3, measurements of their field strengths remain uncertain. In the special case of X-ray-emitting binary pulsars, a direct estimate of the field strength can be obtained by measuring the energy of spectral features that are due to electron cyclotron resonance4-13. With the Ginga satellite observatory14,15, we have measured a cyclotron feature in the hard X-ray spectrum of the 1.24-s binary pulsar Hercules X-1 with a much greater energy resolution than in previous observations4-9. The spectrum from 10-60 keV can be described with a simple analytical formula12,16,17, which indicates an absorption feature at ∼34 keV rather than an emission feature at ∼50keV. From this we estimate the surface magnetic field strength of Her X-1 to be (2.9±0.3) × 1012 G. © 1990 Nature Publishing Group.

DOI： 10.1038/346250a0

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TRANSIENT X-ray sources are generally considered to comprise accreting binary systems containing either a black hole or a neutron star1-5. The transient X-ray emission is thought to result from episodic mass transfer to the compact star
if this is so, transient sources should provide information on the mass-accretion mechanism. On 21 May 1989, the All-Sky Monitor6 (ASM) onboard the satellite Ginga7 discovered an unusual bright X-ray transient source, GS2023+338, in the constellation of Cygnus8. The ASM and Large-Area Counters9 (LAC), also on Ginga, have since monitored the source. Here we report the light curves and spectral evolution observed by the ASM and LAC. From 21 May to 1 June, the intensity varied by up to a factor of 500 on timescales from a few seconds to a few days10. Subsequently the rapid variations persisted, whereas slower ones disappeared. The spectral data fit a power-law model with a photon index of 0.0 to -2.5 and an absorption column density of 1021.7-1022.8 H atoms cm-2. This unusual behaviour remains to be explained. © 1989 Nature Publishing Group.

DOI： 10.1038/342518a0

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We have fabricated multilayer reflectors of molybdenum-carbon, molybdenum-silicon, and nickel-carbon for x rays of 1-200 Å with an electron beam evaporation method in ultrahigh vacuum. The multilayers were deposited on flat and figured substrates of float glass and superpolished glass with a surface roughness of 2-3 Å (rms). The thickness of a layer pair and the number of layer pairs were 30-100 Å and 10-20, respectively. The x-ray characteristics of these multilayer reflectors were evaluated in the 1.5-200 Å region with characteristic x rays (Cu-Kα, Si-Kα, Al-Kα, and C-Kα) and monochromatized synchrotron radiation. Peak reflectivities of molybdenum-carbon were found to be 70% at Cu-Kα and 40% at Al-Kα in grazing incidence and those of molybdenum-silicon to be more than 30% in the 150-170 Å band in near-normal incidence. On the basis of these experimental results, the x-ray optical properties of multilayers are discussed.

DOI： 10.1063/1.1140861

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

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DOI： 10.1063/1.3696187

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We have developed the back-illuminated X-ray CCD camera (BI-CCD) to observe X-ray in space. The X-ray CCD has a sensitivity not only for in X-ray but also in both Optical and UV light, X-ray CCD has to equip a filter to cut off optical light as well as UV light. The X-ray Imaging Spectrometer (XIS) onboard Suzaku satellite equipped with a thin film (OBF : Optical Blocking Filter) to cut off optical light and UV light. OBF is always in danger tearing by the acousmato or vibration during the launch, and it is difficult to handle on the ground because of its thickness. Instead of OBF, we have newly developed and produced OBL (Optical Blocking Layer), which is directly coating on the X-ray CCD surface.

DOI： 10.1063/1.3696190

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We have newly developed the back-illuminated (BI)-CCD which has an Optical Blocking Layer (OBL) directly coating its X-ray illumination surface with Aluminum-Polyimide-Aluminum instead of Optical Blocking Filter (OBF). OBL is composed of a thin polyimide layer sandwiched by two Al layers. Al and Polyimide has a capability to cut visible light and EUV, respectively. To evaluate the performance of OBL that cut off EUV as well as transmit soft X-ray, we measured the EUV and Soft X-ray transmission of both OBL at various energy range between 15-2000 eV by utilizing beam line located at the Photon Factory in High Energy Accelerator Research Organization. We obtained the EUV transmission to be similar to 3% at 41eV which is as same as expected transmission from the designed thickness of polyimide layer, and found no significant change of the EUV transmission of polyimide found during 9month. We also obtained the Soft X-ray transmission of OBL, and found the X-ray transmission of OBL was consistent with the result expected from the thickness of OBL. We also measured the Optical transmission of OBL between 500-900 nm to evaluate the performance of Al that cut off optical light, and obtained the optical transmission to be less than 4x10(-5).

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Physical Society of Japan held an urgent symposium, in order to discuss the utilization of nuclear power and future energy problem, with members of the society and related scientists. We make a brief report of its contents.

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Physical Society of Japan held an urgent symposium, in order to discuss the utilization of nuclear power and future energy problem, with members of the society and related scientists. We make a brief report of its contents.

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We give overview and the current status of the development of the Soft X-ray Imager (SXI) onboard the NeXT satellite. SXI is an X-ray CCD camera placed at the focal plane detector of the Soft X-ray Telescopes for Imaging (SXT-I) onboard NeXT. The pixel size and the format of the CCD is 24 × 24μm (IA) and 2048 × 2048 × 2 (IA+FS). Currently, we have been developing two types of CCD as candidates for SXI, in parallel. The one is front illumination type CCD with moderate thickness of the depletion layer (70 ∼ 100μm) as a baseline plan. The other one is the goal plan, in which we develop back illumination type CCD with a thick depletion layer (200 ∼ 300μm). For the baseline plan, we successfully developed the proto model 'CCD-NeXT1' with the pixel size of 12μm × 12μm and the CCD size of 24mm × 48mm. The depletion layer of the CCD has reached 75 ∼ 85μm. The goal plan is realized by introduction of a new type of CCD 'P-channel CCD', which collects holes in stead of electrons in the common 'N-channel CCD'. By processing a test model of P-channel CCD we have confirmed high quantum efficiency above 10 keV with an equivalent depletion layer of 300μm. A back illumination type of P-channel CCD with a depletion layer of 200μm with aluminum coating for optical blocking has been also successfully developed. We have been also developing a thermo-electric cooler (TEC) with the function of the mechanically support of the CCD wafer without standoff insulators, for the purpose of the reduction of thermal input to the CCD through the standoff insulators. We have been considering the sensor housing and the onboard electronics for the CCD clocking, readout and digital processing of the frame date.

DOI： 10.1117/12.670649

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The NeXT mission has been proposed to study high-energy non-thermal phenomena in the universe. The high-energy response of the super mirror will enable us to perform the first sensitive imaging observations up to 80 keV. The focal plane detector, which combines a fully depleted X-ray CCD and a pixelated CdTe detector, will provide spectra and images in the wide energy range from 0. 5 keV to 80 keV. In the soft gamma-ray band upto ∼ 1 MeV, a narrow field-of-view Compton gamma-ray telescope utilizing several tens of layers of thin Si or CdTe detector will provide precise spectra with much higher sensitivity than present instruments. The continuum sensitivity will reach several x 10-8 photons/s/keV/cm2 in the hard X-ray region and a few × 107 photons/s/keV/cm2 in the soft γ-ray region.

DOI： 10.1117/12.551500

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We report on design updates for the XIS (X-ray Imaging Spectrometer) on-board the Astro-E2 satellite. Astro-E2 is a recovery mission of Astro-E, which was lost during launch in 2000. Astro-E2 carries a total of 5 X-ray telescopes, 4 of which have XIS sensors as their focal plane detectors. Each XIS CCD camera covers a field of view of 19 × 19 arcmin in the energy range of 0.4-12 keV. The design of the Astro-E2 XIS is basically the same as that for Astro-E, but some improvements will be implemented. These are (1) CCD charge injection capability. (2) a revised heat-sink assembly, and (3) addition of a 55Fe radio-isotope on the door. Charge injection may be used to compensate for and calibrate radiation-induced degradation of the CCD charge transfer efficiency. This degradation is expected to become significant after a few year's operation in space. The new heat-sink assembly is expected to increase the mechanical reliability and cooling capability of the XIS sensor. The new radio-isotope on the door will provide better calibration data. We present details of these improvements and summarize the overall design of the XIS.

DOI： 10.1117/12.461313

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Language：Japanese   Publisher：宇宙科学研究所  

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We report 1-20 keV monitoring of the black hole candidate Cyg X-l by the Ginga ah-sky monitor (ASM), in 339 observations spanning from 1987 February to 1991 October. Cyg X-l was in the X-ray low state in the entire 4.5 yr period. Flux modulation at the 5.6 days orbital period was observed dearly (if we assume no periodic variation, reduced chi(2) value is 7.1) in the low-energy (1-2.1 keV) band. In the higher energy band, the modulation amplitude was small and less significant. The 1-2.1 keV folded light curve is a smooth function of the 5.6 days phase. These facts suggest that the modulation is caused by the orbital variation in the column density of photoelectrically absorbing circumstellar matter, as might be expected from the wind of the companion O9.7 Iab star, HDE 226868. The analysis of the spectral modulation suggests that the absorbing wind is not homogeneous. The similar to 300 days periodicity, reported previously by the Vela 5B investigators, was studied. Approximately 150 days periodicity, rather than similar to 300 days, was suggested in our data. Also, a broad peak around similar to 210-230 days period was found in both the power spectral density and the epoch-folding analysis. These periodicities seem to be unstable in their periods. The time-averaged 1-20 keV spectrum from the Ginga ASM alone can be characterized by a power law. However, the combined spectrum measured by Ginga in the 1-20 keV range and by the Solar Maximum Mission (SMM) hard X-ray and burst spectrometer (HXRBS), in the 25-400 keV range in 1987-1988 would require a more complex model, such as the unsaturated Comptonization model.

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We measure various spectral response characteristics around the oxygen and silicon K absorption edges of a Charge-Coupled-Devise (CCD) X-ray detector used in the X-ray Imaging Spectrometer (XIS) developed for the ASTRO-E mission. We have evaluated X-ray Absorption Fine Structure (XAFS) around oxygen K edge in detail. A strong absorption peak of 45% is confirmed just above the oxygen Kedge and an oscillatory structure follows whose amplitude decreases from 20% at the edge to less than 1% at 0.9 keV. We also show XAFS and discuss on a change of the response function around the silicon K edge. The discontinuity of the signal pulse height at the silicon K edge is less than 1.8 eV. We determine the thickness of silicon, silicon dioxide, and silicon nitride in the dead layer using the depth of the absorption edge.

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Soft X-ray response of the CCD camera (XIS, X-ray Imaging Spectrometer), which will be aboard the Astro-E satellite, was investigated for the monochromatic;X-rays in the 0.25-2.2 keV. Detailed pulse-height distribution was examined particularly for O-K line, where significant low-energy tail was found. With the aid of Monte Carlo simulation we found that the photons absorbed in the channel stop was responsible for the component.

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The ASTRO-E X-ray Imaging Spectrometers (XISs) consists of four sets of X-ray CCD camera for the ASTRO-E mission. The XISs have been calibrated at Osaka University: KJ oto University, ISAS and MIT. The calibration experiment. at, Osaka focuses on the soft, X-ray response of the XIS (from 0.25 to 2.2 keV).
The calibration of the XIS Flight Model (XIS FM) has been performed since: August 1998. We measured the signal-pulse height, the energy resolution and the quantum efficiency of the XIS as a function of energy of which are essential to construct the response function of the XIS. The detailed shape of the pulse-height-distribution, are also investigated.
We also constructed a numerical simulator of the XIS, which tracks the physical processes in the CCD so as to reproduce the measured data. With a help of this simulator, we propose a model for the pulse-height-distribution of the XIS for single energy incident X-rays. The model consists of four components; two Gaussians, a constant, plus a triangle-shape component.

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We report the X-ray quantum efficiency of the XIS (X-ray Imaging Spectrometer) in the soft. X-ray band between 0.5 keV and 2.2 keV. We also report the X-ray and optical transmission of the OBF(Optical Blocking Filter). We obtained the quantum efficiency of the XIS of similar to 0.25 at 0.53 keV (O K alpha) and similar to 0.9 at 1.74 keV (Si K alpha). We also obtained the X-ray transmission of similar to 0.65 at O K alpha and optical transmission below 5x10(-5) in the range 400-950nm.

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We report a measurement of the quantum efficiency of a charge coupled device (CCD) with a simple method and report a resultant quantum efficiency in the energy range from 0.47 to 9 keV. The CCD is a front side illuminated device and is fabricated by Hamamatsu Photonics K.K. The quantum efficiency for 4.5 keV x rays is 11% for the single pixel events, 33% for the spectroscopic events, and 60% for flux mode operation. We present the quantum efficiency as a function of the energy. (C) 1998 American Institute of Physics. [S0034-6748(98)02911-6].

DOI： 10.1063/1.1149173

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DOI： 10.1002/asna.2123190127

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The long-term X-ray light curve of Centaurus X-3 and its pulse-period history, which were obtained by the All Sky Monitor on board the Ginga satellite from 1987 February to 1991 October, are presented. The pulse-period history shows a monotonic spin-up overlapping a roughly sinusoidal wave structure with a period of 9.23 +/- 0.14 yr. The observed light curve shows no correlation with the spin-up history. Since Cen X-3 is considered to be a disk-fed X-ray pulsar, the mass accretion affects the pulse period by means of angular-momentum transfer onto the neutron star. In the absence of a correlation between the light curve and pulse period, we conclude that the observed intensity does not represent the mass accretion rate.

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We have studied the iron line intensity variation of Her X-l over its characteristic periodicities such as the pulse period of 1.24 s, the orbital period of 1.7 days, and the long-term period of 35 days, with Ginga observations made from 1989 April to June. From an analysis of the pulse phase-resolved spectra obtained from the MAIN HIGH state of Her X-l, we discover that the line flux modulates from (4.3 +/- 1.9) x 10(-3) to (1.0 +/- 0.3) x 10(-2) photons cm(-2) s(-1) (the average 7.5 x 10(-3) cm(-2) s(-1)) during the pulse period. We also find that the line flux modulation is consistent with that of soft X-rays below 1 keV observed by previous authors. From the study of the orbital phase and the 35 day cycle dependences, we see the following facts: (1) the line flux observed during the high intensity state of Her X-l does not depend significantly on the orbital phase of 0.2-0.9, while the flux is almost invisible during the eclipse, (2) the pattern of the iron line flux modulation along the 35 day cycle is very similar to that of the continuum X-ray flux. With the line pulsations and the solid angle required to explain the equivalent width of the line in the MAIN HIGH state, we deduce that the extent of reprocessing site is less than 10(10) cm. Based on the similarity of the modulation pattern between the line flux and the continuum flux along the 35 day cycle, and the equivalent width change, we suggest that the line flux variation is mainly due to occultation of the reprocessing site by an accretion disk rather than to a change of reprocessing site; some line flux, very small compared with the MAIN HIGH line flux, from an additional site may be responsible for the equivalent width change.

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An ASCA observation of the Jovian impact of the comet Shoemaker-Levy 9 is reported. Four impacts of H, L, Q1 and R were observed and four impacts of B, C, G, and Q2 were observed within 60 minutes after their impacts. No significant flaring of X-ray emission was observed. Upper limit X-ray fluxes of 90 % confidence level, averaged 5 minutes just after the impacts, were 2.4 x 10(-13) erg sec(-1) cm(-2), 3.5 X 10(-13) erg sec(-1) cm(-2), 1.6 X 10(-13) erg sec(-1) cm(-2) and 2.9 x 10(-13) erg sec(-1) cm(-2) for the impacts of H, L, Q1 and R, respectively, in the 0.5(0.7 for H and Q1)-10 keV energy range. However, a hint of X-ray enhancement around Jupiter from July 17 to July 19 was detected with about 2 similar to 6 x 10(-14) erg sec(-1) cm(-2) in the 0.5-10 keV energy range.

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A bright X-ray nova: GS 1124-683 was discovered by the All Sky Monitor (ASM) on board Ginga on 1991 January 8. X-ray properties observed with the ASM from 1991 January 5 to the end of August are presented. The observed spectra were roughly described by a two-component model consisting of a power-law (a hard X-ray) and a disk-blackbody or a blackbody (a soft X-ray) component. In its rising phase, the hard X-ray component appeared first and the soft X-ray component followed with increase of the temperature and the emission area. After the maximum, the intensity of the energy range 1-6 keV decayed exponentially with a time constant of 31.2 +/- 0.1 days, whereas the hard component fell off more rapidly with a time constant of approximately 13 days. The state where the hard component has an appreciable fraction of the energy flux can be recognized as a very high state, which is observed in GX 339-4. With the decay of the hard X-ray component, GS 1124-683 would transfer to the so-called high state. The decay of the soft component can be interpreted to be due to the decrease of temperature of the soft X-ray component. On 70 days after the maximum, a hump of the intensity was observed. About 140 days after the maximum the spectrum becomes hard and would change into the so-called low state. Similar behaviors are observed from two ultrasoft transient sources, A0620-00 and GS 2000+25, therefore such behaviors are considered to be common for bright ultrasoft transient sources.

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We observed the energy spectrum and the time variation of the X-rays from X1850-087 in the globular cluster NGC 6712 with the Large Area Counter on board Ginga. The luminosity of X1850-087, when we observed it, was 1.3 x 10(36) (D/6.8 kpc)2 ergs s-1. The X-ray energy spectrum can be represented by a single power-law type spectrum with a photon index of 2.3, with an interstellar absorption of less than 10(21) H atoms cm-2. A model consisting of disk blackbody and radiation from the neutron star requires an unphysically small inner-disk-radius and a small emission region on the neutron star surface where allowances have been made for the difference between the color temperature and the effective temperature. On the other hand, a model where the main X-ray formation mechanism is Compton scattering indicates that the plasma, which is responsible for Compton scattering, becomes thin and hot in the low accretion rate state. No significant periodic variation was detected, but a significant variation below 1 Hz was found, which is similar to a high-frequency noise observed in the island state of the atoll sources.

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Cygnus X-1 has long been known as a the black hole candidate, whose X-ray flux shows rapid variability on many time scales. Its X-rays have long been considered to be due to inverse Compton scattering of low energy photons by a high temperature plasma clound of 10^8&acd;10^9K situated near the black hole. In this case, time variations of high energy X-rays are expected to be delayed with respect to those of lower energy X-rays. Complex cross spectrum analysis of Cygnus X-1 data taken with the large area proportional counters (LAC) onboard Ginga revealed that the time delay of the high energy X-rays with respect to the lower energy X-rays increases from about 2 msec to several sec for periods from 0.1 sec to 300 sec. This result is inconsistent with the inverse Compton scattering model of Cygnus X-1. The time lag is different in its sign from those in the low mass (QPO) X-ray stars which contain neutron stars. This seems to be explained by the fact that the X-ray emitting plasma is heating up near the black hole and disappears suddenly into the black hole. The phase lag always showed similar time behavior even if the energy ranges and observing times were different, and its characteristic time constants were about 0.1 sec, 3 sec and 10 sec.

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Language：Japanese   Publisher：Japan Aerospace Exploration Agency  

We report here the discovery with the All Sky Monitor Detector on board the GINGA satellite of the X-ray transient, GS2000+25,which appeared in the constellation Vulpecula on 23 April, 1988. The maximum observed intensity was 12 Crab (1-6keV). Two stars in the X-ray error box appeared to increase from the epoch of the Palomar Observatory Sky Survey; one of these was confirmed to be the counterpart by optical spectra and radio measurements. The X-ray spectrum and light curve during the decay phase shows that it belongs to a class of ultra-soft sources which include black hole candidates like A 0620-00. A detailed comparison with A 0620-00 supports the identification of GS2000+25 as a possible new black hole candidate.

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Language：English   Publisher：UNIV CHICAGO PRESS  

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Language：English   Publisher：UNIV CHICAGO PRESS  

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：Japanese   Publisher：Japan Aerospace Exploration Agency  

Development of multilayer reflectors makes it possible to apply to the grazing and normal incidence X-ray optic system for the cosmic X-ray observation in 0.1-10keV region. For the grazing incidence X-ray telescope, multilayer reflectors have an advantage to make larger the glancing angle and to extend the energy range up to 10keV in the fixed configuration. The normal incidence X-ray telescope is attainable in the energy range below 0.4keV, though the sensitive energy band is limited by Bragg condition estimated from the layer thickness and the number of layer pairs. Multilayers are also useful optical elements to fabricate the X-ray spectrometer and polarimeter. We are fabricating multilayer reflectors with electron beam evaporation method in ultra-high vacuum. Material combinations are Mo/C, Mo/Si and Ni/C with 5-20 layer pairs and the layer thickness of 31-100A. They are deposited on flat and figured substrates of float glass and superpolished glass with the surface roughness of 2-3A (rms). Multilayers thus fabricated are evaluated by measuring the reflectivity, the wavelength resolution and Bragg angle with three characteristic X-rays of Cu-Kα(1.54A), Si-Kα(7.13A) and C-Kα(44.7A). Further investigations are carried out with the monochromatized synchrotron radiation in 14-250A band. The peak reflectivity of Cu-Kα is obtained to be 80% for Mo/C in the grazing incidence and that of λ160A to be more than 30% for Mo/Si in near normal incidence.

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：English  

CiNii Article

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Language：Japanese   Publisher：一般社団法人日本物理学会  

CiNii Article

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Language：Japanese   Publisher：一般社団法人日本物理学会  

CiNii Article

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Language：Japanese   Publisher：一般社団法人日本物理学会  

CiNii Article

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：Japanese Book type：Other

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Language：Japanese Book type：Other

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