© 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：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：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：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  

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：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：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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© 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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DOI： 10.1117/12.2231784

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DOI： 10.1117/12.2232509

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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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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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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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DOI： 10.1093/pasj/64.5.101

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DOI： 10.1007/s10909-012-0482-1

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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)   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)  

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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)   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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DOI： 10.1117/12.856778

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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 report the detection of superhard (> 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：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：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 > -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 (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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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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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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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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DOI： 10.1093/pasj/60.sp1.S231

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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 (< 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)  

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

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

DOI： 10.1016/j.asr.2007.03.055

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

DOI： 10.1117/12.732293

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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 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：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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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：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：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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DOI： 10.1016/j.nima.2005.01.080

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DOI： 10.1016/j.nima.2005.01.076

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

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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 (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：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：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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DOI： 10.1016/S0168-9002(99)00601-4

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Language：Japanese   Publisher：The Physical Society of Japan  

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Language：Japanese   Publisher：The Physical Society of Japan  

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

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

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DOI： 10.1117/12.670649

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DOI： 10.1117/12.551500

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DOI： 10.1117/12.461313

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