Search

We have investigated supernova remnant (SNR) W 28 using Suzaku archival data, and we report here the results of our spatially resolved analyses. We carried out spectral analyses using a recombining-plasma (RP) model with element-dependent initial ionization temperatures, obtaining ∼0.5 keV for Ne, ∼0.7 keV for Mg, ∼1.0 keV for Si, ∼1.2 keV for S, ∼1.4 keV for Ar, ∼1.7 keV for Ca, and ∼0.7 keV for Fe in the initial RP phase. In addition to the north-east regions where RPs have been reported previously, we find that the ionization temperatures in the south-east and south-west regions exhibit trends that are similar to those in the central region in the initial RP phase. We also find that the time elapsed from the initial phase of the RP to the present is shorter in the central region, ∼300 yr, and longer in the outside regions, ∼103–104 yr. Our results cannot be explained by simple scenarios involving thermal conduction into molecular clouds or by adiabatic cooling (due to rarefaction), indicating that more complex mechanisms or other scenarios are required. We also estimate the ejecta mass to be ≳14 M⊙, which indicates that this SNR was produced by a massive star.

The Galactic ridge X-ray emission (GRXE) is unresolved X-ray emission located on the Galactic plane, and whether the GRXE comes from truly diffuse plasma or unresolved point sources is still debatable. We present results of spectral analysis of the GRXE with Suzaku. In order to examine the point source origin, we fitted the GRXE spectra in the 1.2–10 keV energy band with a point source model, which is a mixture of active binary stars (ABs) and non-magnetic cataclysmic variables (non-mCVs), and found that the model cannot represent the GRXE spectral shape as long as the standard metal abundances of these species are assumed. In particular, the standard abundance model cannot account for the observed intensities of Si, S, and Ar lines as well as the previously reported Fe line. Assuming spatial densities in the solar neighborhood, integration of the ABs and non-mCVs accounts for only 30% of the observed GRXE flux. Other species of the point sources or diffuse emission with stronger Si, S, Ar, and Fe emission lines shall explain the rest.

In this multi-messenger astronomy era, all the observational probes are improving their sensitivities and overall performance. The Focusing on Relativistic universe and Cosmic Evolution (FORCE) mission, the product of a JAXA/NASA collaboration, will reach a 10 times higher sensitivity in the hard X-ray band ($E >$ 10~keV) in comparison with any previous hard X-ray missions, and provide simultaneous soft X-ray coverage. FORCE aims to be launched in the early 2030s, providing a perfect hard X-ray complement to the ESA flagship mission Athena. FORCE will be the most powerful X-ray probe for discovering obscured/hidden black holes and studying high energy particle acceleration in our Universe and will address how relativistic processes in the universe are realized and how these affect cosmic evolution. FORCE, which will operate over 1--79 keV, is equipped with two identical pairs of supermirrors and wideband X-ray imagers. The mirror and imager are connected by a high mechanical stiffness extensible optical bench with alignment monitor systems with a focal length of 12~m. A light-weight silicon mirror with multi-layer coating realizes a high angular resolution of $, 12 pages, 8 figures. Proceedings of SPIE Astronomical Telescopes and Instrumentation 2022

In this paper, we investigated the Fe K-shell lines in the supernova remnant W51C and hard X-ray sources in the proximity. We measured the intensities of Fe I K$\alpha$ and Fe XXV He$\alpha$ lines at 6.40 keV and 6.68 keV, respectively, and found that the intensity of the 6.68 keV line is consistent with the background level expected from previous studies, while that of the 6.40 keV line is higher at the significance level of 2.0${\sigma}$. Given the presence of gamma-ray emission and high ionization rate point spatially coincident with the remnant, we conclude that the enhanced 6.40 keV line most likely originates from the interaction between low-energy cosmic rays and molecular clouds. Also, we discovered an enhanced 6.68 keV line emission from the compact H II region G49.0-0.3 at the significance level of 3.4${\sigma}$. Spectral analysis revealed that the temperature and abundance of the thermal plasma with the 6.68 keV line is $kT = 3.0^{+0.8}_{-0.7}$ keV and $Z = 0.5 \pm 0.2$ solar, respectively. These values are explained by the thermal plasma generated by the stellar winds of O stars., Comment: 8 pages, 4 figures, accepted for publication in Publications of the Astronomical Society of Japan (PASJ)

XRISM is an X-ray astronomical mission by the JAXA, NASA, ESA and other international participants, that is planned for launch in 2022 (Japanese fiscal year), to quickly restore high-resolution X-ray spectroscopy of astrophysical objects. To enhance the scientific outputs of the mission, the Science Operations Team (SOT) is structured independently from the instrument teams and the Mission Operations Team. The responsibilities of the SOT are divided into four categories: 1) guest observer program and data distributions, 2) distribution of analysis software and the calibration database, 3) guest observer support activities, and 4) performance verification and optimization activities. As the first step, lessons on the science operations learned from past Japanese X-ray missions are reviewed, and 15 kinds of lessons are identified. Among them, a) the importance of early preparation of the operations from the ground stage, b) construction of an independent team for science operations separate from the instrument development, and c) operations with well-defined duties by appointed members are recognized as key lessons. Then, the team structure and the task division between the mission and science operations are defined; the tasks are shared among Japan, US, and Europe and are performed by three centers, the SOC, SDC, and ESAC, respectively. The SOC is designed to perform tasks close to the spacecraft operations, such as spacecraft planning, quick-look health checks, pre-pipeline processing, etc., and the SDC covers tasks regarding data calibration processing, maintenance of analysis tools, etc. The data-archive and user-support activities are covered both by the SOC and SDC. Finally, the science-operations tasks and tools are defined and prepared before launch., Comment: 42 pages, 7 figures, 8 table, Accepted for Publication in JATIS (SPIE)

This paper reports that the X-ray spectrum from the Galactic Center X-ray Emission (GCXE) is expressed by the assembly of active binaries, non-magnetic Cataclysmic Variables, magnetic Cataclysmic Variables (X-ray active star: XAS), cold matter and diffuse sources. In the fitting of the limited components of the XASs, the GCXE spectrum exhibits significant excesses with $\chi^2/d.o.f. =5.67$. The excesses are found at the energies of K$\alpha$, He$\alpha$, Ly$\alpha$ and radiative recombination continuum of S, Fe and Ni. By adding components of the cold matter and the diffuse sources, the GCXE spectrum is nicely reproduced with $\chi^2/d.o.f. = 1.53$, which is a first quantitative model for the origin of the GCXE spectrum. The drastic improvement is mainly due to the recombining plasmas in the diffuse sources, which indicate the presence of high-energy activity of Sgr A$^*$ in the past of $> 1000$~years., Comment: 7 pages, 3 figures, accepted to PASJ. Unit of EW6.4 in tables 3 and 4 were modified

We report current status of developing Soft X-ray Imager (SXI), the X-ray CCD camera onboard X-Ray Imaging and Spectroscopy Mission (XRISM). Four flight model (FM) CCDs have been selected considering several items including energy resolution at 5.9keV, CTI, dark current, etc. We have also completed calibration campaign for all the FM CCDs. Initial analyses show that the response function for monochromatic X-rays is basically the same as that of Hitomi CCDs. The focal plane including the single-stage Stirling cooler has been assembled. Production of key parts in SXI sensor body such as contamination blocking filter and onboard calibration source has been finished and they are waiting for assemble. The digitized signals of the CCD are corrected step by step before conversion to X-ray energy. We are preparing calibration database for the correction such as CTI, gain, and line redistribution function.

The XRISM is the astronomical mission to perform the high-resolution X-ray spectroscopy of astrophysical objects using the micro-calorimeter array. In order to enhance the scientific outputs of the mission, the science operations team (SOT) is structured with responsibilities of the spacecraft planning, data processing and distributions, development and maintenance of analyses software and calibration database, and users’ supports. The operation concepts are established based on lessons learned from past X-ray missions. The SOT consists of the Science Operations Center at JAXA and the Science Data Center at NASA. Details of science operations plan and preparation status on SOC are summarized.

X-Ray Imaging and Spectroscopy Mission (XRISM) is the seventh Japanese X-ray astronomical satellite scheduled to be launched in the Japanese fiscal year 2022. XRISM has two mission instruments, “Resolve”, a soft X-ray spectrometer, and “Xtend”, a soft X-ray imager. The Former is an X-ray micro-calorimeter that has ∼ 5 eV of energy resolution with 3′ × 3 ′ of field of view. The Latter is an X-ray CCD camera with 38′ × 38′ of field of view. Both instruments are placed on the focal plane of X-ray telescopes, X-ray Mirror Assembly (XMA). Xtend CCDs are designed almost the same as those of Hitomi (ASTRO-H), whereas some improvements have been applied. In 2019, flight-model (FM) candidates of Xtend CCDs were fabricated by Hamamatsu Photonics K.K. We performed screening experiments to examine whether they met requirements or not, and then selected the best four chips as the FM. We then performed on-ground calibration on August 2019 and September 2019 for the FM chips to determine the gain correction parameters and to construct the detector response with several energies of monochromatic X-ray. In this paper, we report screening, selection, and on-ground calibration processes, especially focusing on the response verification.

The X-Ray Imaging and Spectroscopy Mission, XRISM, is scheduled to launch in 2022, with the goal of building on the brief successes of the ASTRO-H (Hitomi) mission, and recovering the prime science objective to solve outstanding astrophysical questions using high resolution X-ray spectroscopy. The XRISM Science Operations Team (SOT), consists of the JAXA-led Science Operations Center (SOC) and NASA-led Science Data Center (SDC) that work together to optimize the scientific output from the Resolve high-resolution spectrometer and the Xtend wide-field imager through planning and scheduling observations, processing and distribution of data, development and distribution of software tools and the calibration database (CaldB), user support, and support of ground and in-flight calibration. Here, we summarize the roles and responsibilities of the SDC, and the current status and future plans, covering scheduling software, software and CalDB production and release, data transmission and processing pipeline, and simulation and other post-pipeline analysis tools. Resolve poses particular challenges due to its unprecedented combination of high spectral resolution and throughput, broad spectral coverage, and relatively small field-of-view and large pixel-size; and, we highlight those challenges.

We present the concept of a future Japan-lead X-ray mission, FORCE (Focusing On Relativistic universe and Cosmic Evolution). FORCE is characterized by broadband (1-80 keV) X-ray imaging spectroscopy with high angular resolution (

We report the discovery of an annular emission of $\sim$3'-9' radius around the center of a transient source, an X-ray burster MAXI J1421-613, in the Suzaku follow-up analysis. The spectrum of the annular emission shows no significant emission-line structure, and is well explained by an absorbed power law model with a photon index of $\sim$4.2. These features exclude the possibility that the annular emission is a shell-like component of a supernova remnant. The spectral shape, the time history, and the X-ray flux of the annular emission agree with the scenario that the emission is due to a dust-scattering echo. The annular emission is made under a rare condition of the dust-scattering echo, where the central X-ray source, MAXI J1421-613, exhibits a short time outburst with three X-ray bursts and immediately re-enters a long quiescent period. The distribution of the hydrogen column density along the annular emission follows that of the CO intensity, which means that MAXI J1421-613 is located behind the CO cloud. We estimate the distance to MAXI J1421-613 to be $\sim$3~kpc assuming that the dust layer responsible for the annular emission is located at the same position as the CO cloud., Comment: 11 pages, 3 figures, accepted for publication in Publications of the Astronomical Society of Japan (PASJ)

This paper reports the analysis procedure and results of simultaneous spectral fits of the Suzaku archive data for Sagittarius (Sgr) A East and the nearby Galactic center X-ray emission (GCXE). The results are that the mixed-morphology supernova remnant Sgr A East has a recombining plasma (RP) with Cr and Mn He$\alpha$ lines, and a power-law component (PL) with an Fe I K$\alpha$ line. The nearby GCXE has a $\sim$1.5-times larger surface brightness than the mean GCXE far from Sgr A East, although the spectral shape is almost identical. Based on these results, we interpret that the origins of the RP and the PL with the Fe I K$\alpha$ line are past big flares of Sgr A$^*$., Comment: Accepted for publication in PASJ

We report a discovery of bright blob-like enhancements of an Fe I K$\alpha$ line in the northwest and the middle of the supernova remnant (SNR) IC 443. The distribution of the line emission is associated with molecular clouds interacting with the shock front, and is totally different from that of the plasma. The Fe I K$\alpha$ line has a large equivalent width. The most plausible scenario for the origin of the line emission is that the MeV protons accelerated in the shell leak into the molecular clouds and ionize the Fe atoms therein. The observed Fe I K$\alpha$ line intensity is consistent with the prediction of a theoretical model, in which MeV protons are accelerated along with GeV and TeV protons at the SNR., Comment: 13 pages, 3 figures, accepted for publication in PASJ

X-ray Imaging Spectroscopy Mission (XRISM) is the next Japanese X-ray astronomical satellite to be launched in 2021 Japanese fiscal year. We are developing one of the XRISM instruments “Xtend”, which is an X-ray CCD camera combined with an X-ray telescope, and achieves the wide field of view of 3 8 ′ × 3 8 ′ in 0.4–13 keV. In 2019, twelve flight-model (FM) candidate CCD chips were fabricated by Hamamatsu Photonics K.K. We conducted screening experiments to examine whether the FM candidates met requirements for the Xtend CCDs, and selected the four FM chips from them. We constructed a screening system, with which we can examine various CCD performances by illuminating characteristic X-ray lines in a ∼ 0 . 5 –14 keV band or optical lights. With this system, all the twelve candidates were confirmed to satisfy the requirements. We then selected four chips with the best performance, in terms of e.g., their charge transfer inefficiencies, energy resolutions, soft X-ray sensitivities, and optical light leakages. In this paper, we report an overview of the screening system, and procedures and results of the screening process.

X-ray Astronomy Recovery Mission (XARM) scheduled to be launched in early 2020’s carries two soft X-ray telescopes. One is Resolve consisting of a soft X-ray mirror and a micro calorimeter array, and the other is Soft X-ray Imaging Telescope (Xtend), a combination of an X-ray mirror assembly (XMA) and an X-ray CCD camera (SXI). Xtend covers a field of view (FOV) of 38′ × 38′ , much larger than that of Resolve (3′ × 3 ′ ) with moderate energy resolution in the energy band from 0.4 keV to 13 keV, which is similar to that of Resolve (from 0.3 keV to 12 keV). Simultaneous observations of both telescopes provide complimentary data of X-ray sources in their FOV. In particular, monitoring X-ray sources outside the Resolve FOV but inside the Xtend FOV is important to enhance the reliability of super high resolution spectra obtained with Resolve. Xtend is also expected to be one of the best instruments for low surface brightness X-ray emissions with its low non X-ray background level, which is comparable to that of Suzaku XIS. The design of Xtend is almost identical to those of Soft X-ray Telescope (SXT) and Soft X-ray Imager (SXI) both on board the Hitomi satellite. However, several mandatory updates are included. Updates for the CCD chips are verified with experiment using test CCD chips before finalizing the design of the flight model CCD. Fabrication of the foils for XMA has started, and flight model production of the SXI is almost ready.

The ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi,“Resolving astrophysical problems by precise high-resolution X-ray spectroscopy”.1 This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission’s initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020’s and 2030’s. Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: “Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects”. To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 × 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.

The Galactic Center X-ray Emission (GCXE) is composed of high temperature (7 keV) and low temperature (1 keV) plasmas (HTP and LTP, respectively). The global structure of the HTP is roughly uniform over the Galactic center (GC) region, and the origin of the HTP has been extensively studied. On the other hand, the LTP is more clumpy, and the origin has not been studied in detail. In the S XV He alpha line map, a pair of horn-like soft diffuse sources are seen at the symmetric positions with respect to Sagittarius A^{star}. The X-ray spectra of the pair are well represented by an absorbed thin thermal plasma model of a temperature and N_H of 0.6-0.7 keV and 4x10^{22} cm^{-2}, respectively. The N_H values indicate that the pair are located near at the GC. Then the dynamical time scales of the pair are 10^{5} yr. The Si and S abundances and the surface brightnesses in the S XV He alpha line band are 0.7-1.2 and 0.6-1.3 solar, and (2.0-2.4)x10^{-15} erg s^{-1} cm^{-2} arcmin^{-2}, respectively. The temperature, abundances, and surface brightness are similar to those of the LTP in the GCXE, while the abundances are far larger than those of known point sources, typically coronal active stars and RS CVn-type active binaries. Based on these results, possible origin of the LTP is discussed., Comment: Accepted for publication in PASJ

HESS J1841$-$055 is a diffuse unidentified gamma-ray source with the size of $\sim\,1.3^{\circ}\times\,1^{\circ}$. No conclusive counterpart in other wavelengths has so far detected. To search for X-rays responsible for the TeV emission, the Suzaku observations were conducted, which covered a half region of the HESS source. In the soft band (0.5-2.0 keV), we discovered a diffuse emission, Suzaku J1840.2$-$0552, with the size of $\sim10'$. Since its spectrum was fitted by an optically thin thermal plasma model, Suzaku J1840.2$-$0552 is likely to be a supernova remnant. We also discovered an extended source, Suzaku J1840.2$-$0544, in the hard band (2.0-8.0 keV) with an emission line at 6.1 keV. From the spectral feature and large interstellar absorption, this source is likely to be a cluster of galaxies behind the Galactic plane at the red-shift of $\sim$0.09. The other diffuse source spatially overlaps with the SNR candidate G26.6$-$0.2, which shows a non-thermal dominant spectrum. Since no other candidate is found in the hard X-ray band, we infer that these largely extended sources could be possible counterparts of HESS J1841$-$055., 17 pages, 5 figures

Cosmic rays (CRs) in our galaxy are thought to be generated via diffusive shock acceleration. Gamma-ray observations have revealed that protons and/or electrons are accelerated to energies up to 100 TeV in supernova remnants (SNRs), and hence SNRs are the most plausible source of CR production. Whereas low-energy cosmic rays (LECRs) below the MeV band have important information on the initial acceleration mechanism, there has been very little information on LECRs due to lack of an effective probe. Interacting with neutral iron atoms in the interstellar medium, LECRs produce fluorescent X-ray line emission at 6.40 keV. The 6.40 keV line observation can be a unique probe to investigate LECRs. Analyzing the Suzaku data, we discovered the 6.40 keV line emission from several SNRs interacting with molecular clouds (W28, W44, Kes 67, Kes 69, Kes 78, Kes 79, and 3C391). The 6.40 keV line emission would be produced by MeV protons with the energy density of $>10$ eV cm$^{-3}$. Furthermore, we discovered the 6.40 keV line emission from a giant molecular cloud located near the Galactic center. The energy density of MeV protons is estimated to be 80 eV cm$^{-3}$. The diffusion length of MeV protons is only a few tens of parsecs, and thus the MeV protons should be produced in situ. Surprisingly, there is no SNR in the vicinity. The LECRs would possibly be generated by stochastic acceleration via Alfven turbulence.

We present the discovery of out-flow like plasma emissions with the Suzaku and ASCA data. Those plasmas have a size of ∼150 pc. Remarkably, the southern plasma is in a recombination dominant phase, which is not predicted by standard shock heating. A plausible scenario is either photoionization due to strong jet-like X-rays from Sgr A* or rapid cooling due to adiabatic expansion of a blowout plasma from the Galactic center about 105 years ago.

P-channel charge-coupled devices (CCDs) made from N-type silicon wafers were originally developed for ground-based optical and near-infrared telescopes. The thick depletion layer of these CCDs provides the significant advantage of high quantum efficiency (QE) for hard X-rays. On the other hand, high QE for soft X-rays is obtained with back-illuminated (BI) and fully depleted CCDs in which only a thin dead layer exists on the surface of incidence. Thus, P-channel BI CCDs can be applicable as superior wide band X-ray detectors. We have developed such a device specifically for the Soft X-ray Imager (SXI) on board the X-ray astronomy satellite ASTRO-H, scheduled to be launched in 2014. We previously reported that the depletion layers of our CCDs, a prototype of SXI-CCDs, have a thickness of more than 200 μ m . In this paper, we report a novel soft X-ray response of P-channel BI CCDs. First, we irradiate fluorescent X-rays of O, F, Na, Al, Si and K to the SXI prototype. This experiment reveals that our CCD has a significant low-energy tail structure in the soft X-ray response. Since the intensity of the low-energy tail is larger for lower X-ray energies, the tail is originated on the CCD surface layer. Then, we fabricate a new type of CCDs by applying an alternative treatment to its surface layer. The soft X-ray response of the CCD is measured by irradiation of monochromatic X-rays from 0.25 keV to 1.8 keV in a synchrotron facility, KEK-PF. The intensity of the low-energy tail for 0.5 keV incident X-ray is one order of magnitude smaller than that for the previous CCD. The same treatment will be applied to the surface layer of the SXI flight model.

Astro-H (Hitomi) is an X-ray/Gamma-ray mission led by Japan with international participation, launched on February 17, 2016. The payload consists of four different instruments (SXS, SXI, HXI and SGD) that operate simultaneously to cover the energy range from 0.3 keV up to 600 keV. This paper presents the analysis software and the data processing pipeline created to calibrate and analyze the Hitomi science data along with the plan for the archive and user support. These activities have been a collaborative effort shared between scientists and software engineers working in several institutes in Japan and USA.

This paper reports the analysis of the X-ray spectra of the Galactic diffuse X-ray emission (GDXE) in the Suzaku archive. The fluxes of the Fe I K alpha (6.4 keV), Fe XXV,He alpha (6.7 keV) and Fe XXVI Ly alpha (6.97 keV) lines are separately determined. From the latitude distributions, we confirm that the GDXE is decomposed into the Galactic center (GCXE), the Galactic bulge (GBXE) and the Galactic ridge (GRXE) X-ray emissions. The scale heights (SHs) of the Fe XXV He alpha line of the GCXE, GBXE and GRXE are determined to be ~40, ~310 and ~140 pc, while those of the Fe I K alpha line are ~30, ~160 and ~70 pc, respectively. The mean equivalent widths (EWs) of the sum of the Fe XXV He alpha and Fe XXVI Ly alpha lines are ~750 eV, ~600 eV and ~550 eV, while those of the Fe I K alpha line are ~150~eV, ~60~eV and ~100~eV for the GCXE, GBXE and GRXE, respectively. The origin of the GBXE, GRXE and GCXE is separately discussed based on the new results of the SHs and EWs, in comparison with those of the Cataclysmic Variables (CVs), Active Binaries (ABs) and Coronal Active stars (CAs)., Comment: Accepted for publication in PASJ

We have surveyed spatial profiles of the Fe K$\alpha$ lines in the Galactic center diffuse X-rays (GCDX), including the transient region from the GCDX to the Galactic ridge X-ray emission (GRXE), with the Suzaku satellite. We resolved Fe K$\alpha$ line complex into three lines of Fe \emissiontype{I}, Fe \emissiontype{XXV} and Fe \emissiontype{XXVI} K$\alpha$, and obtained their spatial intensity profiles with the resolution of $\sim \timeform{0D.1}$. We compared the Fe \emissiontype{XXV} K$\alpha$ profile with a stellar mass distribution (SMD) model made from near infrared observations. The intensity profile of Fe \emissiontype{XXV} K$\alpha$ is nicely fitted with the SMD model in the GRXE region, while that in the GCDX region shows $3.8\pm0.3$ $(\timeform{0D.2}, Comment: Accepted by PASJ

Supernova remnants (SNRs) are the primary candidate of Galactic cosmic-ray accelerators. It is still an open issue when and how young SNRs, which typically exhibit strong synchrotron X-rays and GeV and TeV gamma-rays, undergo the state transition to middle-aged SNRs dominated by thermal X-rays and GeV gamma-rays. The SNR N132D in the Large Magellanic Cloud is an ideal target to study such a transition, exhibiting bright X-rays and gamma-rays, and with the expected age of ~2500 yrs. In this paper we present results of NuSTAR and Suzaku spectroscopy. We reveal that N132D has a nearly equilibrium plasma with a temperature of > 5 keV or a recombining plasma with a lower temperature (~1.5 keV) and a recombining timescale (net) of 8.8 (7.0--10.0)e12 cm^-3s. Together with the center filled morphology observed in the iron K line image, our results suggest that N132D is now at transition stage from a young SNR to middle-aged. We have constrained the tight upper-limit of nonthermal X-rays. Bright gamma-rays compared to faint nonthermal X-rays suggest that the gamma-rays are hadronic in origin. The spectral energy distribution from radio to gamma-rays shows a proton cut-off energy of ~30 TeV. These facts confirm that N132D is in the transition from young to middle-aged SNR. The large thermal energy of > 10^51 erg and accelerated proton energy of ~ 10^50 erg suggest the supernova explosion might have been very energetic., 11 pages, 13 figures, ApJ, in press

A 20' \times 16' elliptical ring-like structure has been found near the Galactic center in the narrow energy band corresponding to the K$\alpha$ line from He-like sulfur. In the ring, two diffuse sources are found, a supernova remnant candidate G359.79-0.26 and an unidentified source G359.77-0.09. The X-ray spectrum of G359.77-0.09 is similar to that of G359.79-0.26, which can be explained by an absorbed thin thermal plasma model with temperatures of 0.7 and 1.0 keV. The absorption column densities of these two sources are large (N_H = 6.9 \times 10^{22} and 4.5 \times 10^{22} cm^{-2}) and are consistent with that of the Galactic center distance. The X-ray spectrum extracted from the ring-like structure is also represented by an absorbed thin thermal plasma model (kT_e \sim 0.9 keV). The thermal energy of the plasma filling the ring-like structure is estimated to be 1.0 \times 10^{51} erg. We therefore propose that the two sources comprise a single ring-like object, which is possibly a super bubble with a size of 49 pc \times 40 pc in the Galactic center region., Comment: 9 pages, 7 figures, accepted for publication in PASJ

We report results of the Suzaku observation toward the Sagittarius (Sgr) D region. Diffuse X-ray emission was clearly detected from inside the shell-type supernova remnant, the Sgr D SNR and is named G 1.02-0.18. A hint of an iron line is seen in the spectrum, suggesting that G 1.02-0.18 is a thin thermal plasma with the temperature of kT ∼ 2 keV . Its physical parameters (e.g. the plasma density, mass, thermal energy) suggest that G 1.02-0.18 is an SNR candidate and is possibly associated with the Sgr D SNR. We also analyzed data from another bright X-ray source SAX J1748.2-2808, which was in the field of view of Suzaku. A coherent pulsation with a period of 593 s and emission lines from neutral and highly ionized irons were discovered. These results indicate that SAX J1748.2-2808 is likely to be an intermediate polar.

We present the Suzaku results on a new candidate of a supernova remnant (SNR) in the Sagittarius C region. We detected diffuse X-rays of an elliptical shape (G359.41-0.12) and a chimney-like structure (the Chimney), both of which were fitted with a thin thermal the model of kBT ~1 keV temperature. The absorption columns are same between these two structures, indicating that both are located at the same distance in the same line of sight. The narrow band image and one-dimensional profile of S XV Kalpha at 2.45 keV show that the Chimney is emanating from G359.41-0.12. Therefore, these two sources are physically connected with each other. The sum of the thermal energies of the Chimney and G359.41-0.12 is estimated to be 1.4x10^50 erg, typical for a galactic SNR. G359.41-0.12 is likely to be a new SNR candidate and the Chimney is an associated outflow., 10 pages, 4 figures

This paper reports on the first results of the Suzaku observation in the Sgr C region. We detected four diffuse clumps with strong line emission at 6.4keV, Ka from neutral or low-ionized Fe. One of them, M359.38-0.00, is newly discovered with Suzaku. The X-ray spectra of the two bright clumps, M359.43-0.07 and M359.47-0.15, after subtracting the Galactic center diffuse X-ray emission (GCDX), exhibit strong Ka line from FeI with large equivalent widths (EWs) of 2.0-2.2keV and clear Kb of FeI. The GCDX in the Sgr C region is composed of the 6.4keV- and 6.7keV-associated components. These are phenomenologically decomposed by taking relations between EWs of the 6.4keV and 6.7keV lines. Then the former EWs against the associated continuum in the bright clump regions are estimated to be 2.4(+2.3_-0.7)keV. Since the two different approaches give similar large EWs of 2keV, we strongly suggest that the 6.4keV clumps in the Sgr C region are due to X-ray reflection/fluorescence (the X-ray reflection nebulae).

We report on the diffuse X-ray emission from the Galactic Centre (GCDX) observed with the X-ray Imaging Spectrometer (XIS) on board the Suzaku satellite. The highly accurate energy calibration and extremely low background of the XIS provide many new facts on the GCDX. These are (1) the origin of the lines at 6.7 and 7.0 keV is collisional excitation in a hot plasma, (2) the discovery of new SNR and super-bubble candidates, (3) most of the 6.4 keV line is X-ray fluorescence, and (4) time variability of the 6.4 keV line is found from the Sgr B2 complex. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the diffuse X-ray emissions from the Galactic center (GCDX) observed with the X-ray Imaging Spectrometer (XIS) on board the Suzaku satellite. The highly accurate energy calibrations and extremely low background of the XIS provide many new facts on the GCDX. These are (1) the origin of the 6.7/7.0keV lines is collisional excitation in hot plasma, (2) new SNR and super-bubble candidates are found, (3) most of the 6.4keV line is fluorescence by X-rays, and (4) time variability of the 6.4keV line is found from the SgrB2 complex., Comment: 4 pages, 6 figure, proceedings of the XMM-Newton workshop, June 2007, accepted for publication in AN

The Soft X-ray Imager (SXI) is an X-ray CCD camera onboard the ASTRO-H X-ray observatory. The CCD chip used is a P-channel back-illuminated type, and has a 200-µm thick depletion layer, with which the SXI covers the energy range between 0.4 keV and 12 keV. Its imaging area has a size of 31 mm x 31 mm. We arrange four of the CCD chips in a 2 by 2 grid so that we can cover a large field-of-view of 38’ x 38’. We cool the CCDs to -120 °C with a single-stage Stirling cooler. As was done for the CCD camera of the Suzaku satellite, XIS, artificial charges are injected to selected rows in order to recover charge transfer inefficiency due to radiation damage caused by in-orbit cosmic rays. We completed fabrication of flight models of the SXI and installed them into the satellite. We verified the performance of the SXI in a series of satellite tests. On-ground calibrations were also carried out and detailed studies are ongoing.

Soft X-ray Imager (SXI) is a CCD camera onboard the ASTRO-H satellite which is scheduled to be launched in 2015. The SXI camera contains four CCD chips, each with an imaging area of 31mm x 31 mm, arrayed in mosaic, covering the whole FOV area of 38′ x 38′. The CCDs are a P-channel back-illuminated (BI) type with a depletion layer thickness of 200 _m. High QE of 77% at 10 keV expected for this device is an advantage to cover an overlapping energy band with the Hard X-ray Imager (HXI) onboard ASTRO-H. Most of the flight components of the SXI system are completed until the end of 2013 and assembled, and an end-to-end test is performed. Basic performance is verified to meet the requirements. Similar performance is confirmed in the first integration test of the satellite performed in March to June 2014, in which the energy resolution at 5.9 keV of 160 eV is obtained. In parallel to these activities, calibrations using engineering model CCDs are performed, including QE, transmission of a filter, linearity, and response profiles.

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of Delta E < 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts., 24 pages, 18 figures, Proceedings of the SPIE Astronomical Instrumentation "Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray"

This paper reports detailed K-shell line profiles of iron (Fe) and nickel (Ni) of the Galactic Center X-ray Emission (GCXE), Galactic Bulge X-ray Emission (GBXE), Galactic Ridge X-ray Emission (GRXE), magnetic Cataclysmic Variables (mCVs), non-magnetic Cataclysmic Variables (non-mCVs), and coronally Active Binaries (ABs). For the study of the origin of the GCXE, GBXE, and GRXE, the spectral analysis is focused on equivalent widths of the Fe K$\alpha$, Fe He$\alpha$, and Fe Ly$\alpha$ lines. The global spectrum of the GBXE is reproduced by a combination of the mCVs, non-mCVs, and ABs spectra. On the other hand, the GRXE spectrum shows significant data excesses at the Fe K$\alpha$ and Fe He$\alpha$ line energies. This means that additional components other than mCVs, non-mCVs, and ABs are required, which have symbiotic phenomena of cold gas and very high-temperature plasma. The GCXE spectrum shows larger excesses than those found in the GRXE spectrum at all the K-shell lines of iron and nickel. Among them the largest ones are the Fe K$\alpha$, Fe He$\alpha$, Fe Ly$\alpha$, and Fe Ly$\beta$ lines. Together with the fact that the scale heights of the Fe K$\alpha$, Fe He$\alpha$, and Fe Ly$\alpha$ lines are similar to that of the central molecular zone (CMZ), the excess components would be related to high-energy activity in the extreme envelopment of the CMZ., Comment: 12 pages, 10 figures, 5 tables, published in ApJ

We observed the supergiant fast X-ray transient (SFXT) AX J1841.0-0536 with Suzaku. Many short flares with durations of ~100 s were detected in the XIS and HXD bands. We found that the overall spectrum in the 1.0-40 keV band was fitted with an partially absorbed cut-off power-law plus an Fe I Kα line and an absorption feature at the center energy of ~15 keV, that we interpret as possible evidence of a resonant cyclotron absorption feature. We then made time-resolved spectra and fit them with the same models as the overall spectrum. The photon indices of the power-law were distributed in 0-2 with the trend of "harder when brighter". On the other hand, no significant difference was found, either in the absorption column densities nor in the covering fractions between any of the phases.

We have surveyed the spatial profile of the Fe Kα lines in the Galactic center diffuse X-rays (GCDX), including the transient region from the GCDX to the Galactic ridge X-ray emission (GRXE) using the Suzaku XIS data. We compared Fe XXV Kα profile with a stellar mass distribution (SMD) model made from near infrared observations. The Fe XXV Kα profile is nicely fitted with the SMD model in the GRXE region, while that in the GCDX region shows about 4-19 times excess over the best-fit SMD model in the GRXE region. Thus Fe XXV Kα in the GCDX is hardly explained by the same origin of the GRXE.

We present the Suzaku results of the supernova remnant (SNR) G346.6-0.2. The X-ray emission has a center-filled morphology with the size of 6' x 8' within the radio shell. Neither an ionization equilibrium nor non-equilibrium (ionizing) plasma can reproduce the spectra remaining shoulder-like residuals in the 2-4 keV band. These structures are possibly due to recombination of free electrons to the K-shell of He-like Si and S. The X-ray spectra are well fitted with a plasma model in a recombination dominant phase. We propose that the plasma was in nearly full ionized state at high temperature of 5 keV, then the plasma changed to a recombining phase due to selective cooling of electrons to lower temperature of 0.3 keV. G346.6-0.2 would be in an epoch of the recombining phase., Comment: Accepted for publication in PASJ

X-ray Imaging Spectrometer (XIS) onboard Suzaku is equipped with the Spaced-row Charge Injection (SCI) technique in order to suppress charge transfer inefficiency (CTI). The accuracy of the energy-scale has been getting worse. With the systematic analysis of the fiveyear data, we found that the accuracy deterioration is due to the unexpected behaviors of CTI: one is some discontinuous increases of CTI and the other is gradual time variation of its dependency on pulse heights of signal charges. By taking them into account, we upgraded the CTI correction method and achieved high accuracy of the energy scale both in the low and highenergy bands (

We present quantitative investigation on the past activities of Sgr A* from the three dimensional position of multiple X-ray reflection nebulae.

The XIS (X-ray Imaging Spectrometer) on board Suzaku satellite provides two kinds of clocking modes, the Normal and the Parallel-Sum (P-sum) mode. In the P-sum mode, observer can obtain the highest time resolution 8/1024 (~8ms) with XIS. But, the spatial resolution in the Y-direction of the CCD is lost with P-sum mode. Because, in the P-sum mode, the pixel data from multiple rows are summed in the Y-direction on the CCD, and the sum is put in the Pixel RAM as a single row. We have analyzed observed data of E0102-72 which was observed with P-sum mode for calibration purpose have studied the performance of P-sum mode. For seven years after the lunch, we find the gain of both XIS0 and XIS3 p-sum mode data has gradually changed from 3.6eV/ch to 4.2eV/ch. And the energy resolution has also changed from 60eV to 140eV at the energy of NeIX.

There are K-shell emission lines of neutral Fe K (Fe I K) correlated with giant molecular clouds in the Galactic center (GC) region. The Fe I K emission is one of the key for the structure and activity of the GC, including the super-massive black hole Sagittarius A* (hereafter Sgr A*) with a huge mass of four million solar. The origin of the Fe I K is still an open question. In order to resolve the problem, we made deep observations of the GC region with Suzaku. From the high-quality Xray data taken by Suzaku, we have found many clouds emitting the Fe I K line and have revealed the following new facts: (1) emission lines of neutral heavy atoms other than Fe, (2) time variability of the X-ray flux from the molecular clouds, (3) measurement of three-dimensional distribution of the molecular clouds. From these results, we reached a conclusion that Sgr A* made X-ray flares several hundred years ago and illuminated the molecular clouds in the vicinity.