国分 紀秀

Polarization measurements in the hard X-ray band can provide crucial information about high energy emission at astrophysical objects. Such measurements require an instrument with high signal-to-noise ratio and high photon throughput for which the multilayer hard X-ray mirror is ideally suited. Future hard X-ray missions equipped with the multilayer mirror including ASTRO-H (Formerly NeXT) and NuStar are expected to detect hard X-ray sources in the flux range of 10 mu Crab. We expect a polarimeter mission using such mirrors to follow. Reflection off the mirror surface can introduce small but finite artificial polarization at the focal plane. We have conducted an experiment to set an upper limit for such polarization using a polarized hard X-ray beam at SPring-8 in Japan. In the experiment, reflectance of a multilayer surface has been measured as a function of the angle between the scattering plane and the hard X-ray polarization plane. The angular dependence of the measured reflectance can be translated to the artificial polarization. We have derived from the experimental results that the artificial polarization is no more than +/-0.8% at the scattering angle 0.51 degrees. This upper limit ensures that we can measure polarization down to similar to 1% using the multilayer X-ray mirror. (C) 2009 Elsevier B.V. All rights reserved.

We present the first Suzaku observation of the new Soft Gamma Repeater, SGR 0501+4516, performed on 2008 August 26, four days after the onset of bursting activity of this new member of the magnetar family. The soft X-ray persistent emission was detected with the X-ray Imaging Spectrometer (XIS) at a 0.5-10 keV flux of 3.8 x 10-(11) erg s(-1) cm(-2), with a spectrum well fitted by an absorbed blackbody plus power-law model. The source pulsation was confirmed at a period of 5.762072 +/- 0.000002 s, and 32 X-ray bursts were detected by the XIS, four of which were also detected at higher energies by the Hard X-ray Detector (HXD). The strongest burst, which occurred at 03:16:16.9 (UTC), was so bright that it caused instrumental saturation, but its precursor phase, lasting for about 200 ms, was detected successfully over the 0.5-200 keV range, with a fluence of similar to 2.1 x 10(-7) erg cm-2 and a peak intensity of about 89 crab. The entire burst fluence is estimated to be similar to 50 times higher. The precursor spectrum was very hard, and well modeled by a combination of two blackbodies. We discuss the bursting activity and X/gamma-ray properties of this newly discovered Soft Gamma Repeater in comparison with other members of the class.

The Soft Gamma-ray Detector (SGD) on board ASTRO-H (Japanese next high-energy astrophysics mission) is a Compton telescope with narrow field-of-view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (50-600 keV) at a background level 10 times better than that of the Suzaku Hard X-ray Detector, and is complimentary to the Hard X-ray Imager on board ASTRO-H with an energy coverage of 5-80 keV. Excellent energy resolution is the key feature of the SGD, allowing it to achieve good background rejection capability taking advantage of good angular resolution. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of gamma-ray emission processes. Here we describe the instrument design of the SGD, its expected performance, and its development status. ©2009 IEEE.

Tycho's supernova remnant was observed by the XIS and HXD instruments onboard the Suzaku satellite on 2006 June 26-29 for 92 ks. The spectrum up to 30 keV was well fitted with a two-component model, consisting of a power-law with a photon index of 2.7 and a thermal bremsstrahlung model with a temperature of 4.7 keV. The former component can alternatively be modeled as synchrotron emission from a population of relativistic electrons with an estimated roll-off energy of around 1 keV. In the XIS spectra, in addition to the prominent Fe K alpha line (6.445 keV), we observed for the first time significant K alpha line emission from trace species Cr and Mn at energies of 5.48 keV and 5.95 keV, respectively. Faint K beta lines from Ca (4.56 keV) and Fe (7.11 keV) were also seen. The ionization states of Cr and Mn, based on their line centroids, Lire estimated to be similar to that of Fe K alpha (Fe XV or XVI).

The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA sounding rocket mission which will study particle acceleration and coronal heating on the Sun through unprecedented high-resolution imaging in the hard X-ray energy band (5-15 keV). Energy release occurring in the quiet region of the Sun may potentially play an important role in the coronal heating mechanism. With a combination of high-resolution focusing Xray optics and fine-pitch imaging sensors, FOXSI will achieve superior sensitivity; two orders of magnitude better than that of the RHESSI satellite. FOXSI requires the spectral capability down to 5 keV, which requires a development of a new ASIC and detector with a better energy resolution. We plan to use a Double-sided Si Strip Detector (DSSD) with a low-noise front-end ASIC as the FOXSI focal plane detector, which will fulfill the scientific requirements on the spatial resolution, energy resolution, lower threshold energy and time resolution. We have designed and fabricated a DSSD with a thickness of 500 mu m and a dimension of 9.6 mm x 9.6 mm, containing 128 strips separated by a pitch of 75 mu m, which corresponds to 8 arcsec at the focal length of 2 m. The DSSD was successfully operated in a laboratory experiment. Under a temperature of -20 degrees C and a bias voltage of 250 V, we obtained spectra from both sides of the electrodes. The energy resolution was measured to be 980 eV and 2.4 keV for the p-side and n-side at 14 keV gamma-ray, sufficient for the FOXSI mission requirement.

The Suzaku Wide-band All-sky Monitor (WAM) consists of 20 BGO anti-coincidence scintillators for the Hard X-ray Detector (HXD), The WAM has a wide field of view (FOV), about half of the whole sky, a large collecting area, 800 cm(2), and broad-band energy coverage from 50 to 5000 keV. Thus it has been designed to work as a gamma-ray burst detector. For the three years since Suzaku launch in July 2005, the WAM has been working very well. About 500 GRBs have been detected through the end of 2008, corresponding to a detection rate of similar to 140 GRBs per year. The current status of the WAM is presented in this paper.

We are developing imaging Cadmium Telluride (CdTe) pixel detectors optimized for astrophysical hard X-ray applications. Our hybrid detector consist of a CdTe crystal 1mm thick and 2cm × 2cm in area with segmented anode contacts directly bonded to a custom low-noise application specific integrated circuit (ASIC). The CdTe sensor, fabricated by ACRORAD (Okinawa, Japan), has Schottky blocking contacts on a 605 micron pitch in a 32 × 32 array, providing low leakage current and enabling readout of the anode side. The detector is bonded using epoxy-gold stud interconnects to a custom low noise, low power ASIC circuit developed by Caltech's Space Radiation Laboratory. We have achieved very good energy resolution over a wide energy range (0.62keV FWHM @ 60keV, 10.8keV FWHM @ 662keV). We observe polarization effects at room temperature, but they are suppressed if we operate the detector at or below 0°C degree. These detectors have potential application for future missions such as the International X-ray Observatory (IXO). © 2009 Copyright SPIE - The International Society for Optical Engineering.

Although the afterglow observations in HETE-2 and Swift era have revealed a lot of afterglow properties of gamma-ray bursts (GRBs), we still have poor understanding of the prompt gamma-ray emission, such as the emission mechanism of the prompt emission and differences between short and long duration GRBs. We have observed many prompt emission of GRBs by Suzaku Wide-band All-sky Monitor in wide energy range of 50-5000 keV, with very large effective area of 400 cm(2) even at 1 MeV. Furthermore, a combination of the Suzaku/WAM and Swift data provides us not only wider energy range of 15-5000 keV but also redshift information even for some short GRBs. Thanks to these information, we can firstly investigate an intrinsic correlation for short GRBs like E-peak - L-iso relation, and we can derive the same type of relation for time-resolved spectra of long GRBs in finer time-scale with higher statistics than ever before. These results could be used to discuss the differences between short and long GRBs, and our time-resolved E-peak - L-iso relation also could be used as both more appropriate redshift indicator and new probe of the fireball dynamics.

We assume that the energy source in the Galactic Center is the black hole Sgr A^*, which becomes active when a star is captured in a rate of ∼10^-5yr^-1. During the active phase relativistic protons with a characteristic energy ∼6 ×10⁵²erg per capture are ejected. We suppose that the annihilation of secondary positrons produced by proton-proton collisions is observed as the 511 keV line flux from the Galactic bulge. Though these positron are generated with relatively high energies (>30 MeV), our model satisfy the criterion derived by Beacom and Yüksel based on the COMPTEL data in the range 1–30 MeV. From our estimations it follows also that a flux of gamma-ray de-excitation lines ∼2.5 ×10^-5ph cm^-2s^-1in the range below 8 MeV is produced by the relativistic protons in the Galactic center. A specific line is the one at 1.809 MeV from radioactivity of ²⁶Al. The predicted quasi-stationary flux of the ²⁶Al 1.809 MeV line from the 1° ×1° central region is ≤10^-6ph cm^-2s^-1. We conclude also the the thermal 6.5 keV X-ray flux and the non-thermal hard X-ray flux in the range 14–40 keV observed by SUZAKU is emitted by subrelativistic protons produced by accretion processes.

Suzaku Hard X-ray Detector (HXD) achieved the lowest background level than any other previously or currently operational missions sensitive in the energy range of 10-600 keV, by utilizing PIN photodiodes and GSO scintillators; mounted in BGO active shields to reject particle background and Compton-scattered events as much as possible. Because it does not have an imaging capability nor rocking mode for the background monitor, the sensitivity is limited by the reproducibility of the non X-ray background (NXB) model. We modeled the HXD NXB, which varies with time as well as other satellites with a low-Earth orbit, by utilizing several parameters, including particle monitor counts and satellite orbital/attitude information, The model background is supplied as an event file in which the background events are generated by random numbers, and can be analyzed in the same way as the real data. The reproducibility of the NXB model depends on the event selection criteria (such as cut-off rigidity and energy band) and the integration time, and the 1 sigma systematic error is estimated to be less than 3% (PIN 15-40 keV) and 1% (GSO 50-100 keV) for more than 10 ks exposure.

The Suzaku Wide-band All-sky Monitor (WAM) consists of thick BGO anti-coincidence shields of the Hard X-ray Detectors (HXD). It views about half of the sky and has a geometrical area of 800 cm(2) per side and an effective area of 400 cm(2), even at 1 MeV. Hence, the WAM can provide unique opportunities to detect high-energy emission from GRBs and solar flares in the sub-MeV to MeV range. The WAM has detected more than 400 GRBs and 100 solar flares since its launch. This paper describes the in-flight performance of the HXD/WAM during the initial two years of operations, including the in-flight energy response, spectral and timing capabilities, and in-orbit background.

The Soft Gamma-ray Detector (SGD) on board ASTRO-H (Japanese next high-energy astrophysics mission) is a Compton telescope with narrow field-of-view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (50-600 keV) at a background level 10 times better than that of the Suzaku Hard X-ray Detector, and is complimentary to the Hard X-ray Imager on board ASTRO-H with an energy coverage of 5-80 keV. Excellent energy resolution is the key feature of the SGD, allowing it to achieve good background rejection capability taking advantage of good angular resolution. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of gamma-ray emission processes. Here we describe the instrument design of the SGD, its expected performance, and its development status. ©2009 IEEE.

Clusters of galaxies are among the best candidates for particle acceleration sources in the universe, a signature of which is non-thermal hard X-ray emission from the accelerated relativistic particles. We present early results on Suzaku observations of non-thermal emission from Abell 3376, which is a nearby on-going merger cluster. Suzaku observed the cluster twice, while focusing on the cluster center containing the diffuse radio emission to the east, and a cluster peripheral region to the west. For both observations, we detected no excess hard X-ray emission above the thermal cluster emission. An upper limit on the non-thermal X-ray flux of 2.1 x 10-(11) erg cm(-2) s(-1) (15-50 keV) at the 3 sigma level from a 34' x 34' region, derived with the Hard X-ray Detector (HXD), is similar to that obtained with the BeppoSAX/PDS. Using the X-ray Imaging Spectrometer (XIS) data, the upper limit on the non-thermal emission from the West Relic is independently constrained to be < 1.1 x 10(-12) ergs(-1) cm(-2) (4-8 keV) at the 3 sigma level from a 122 arcmin(2) region. Assuming Compton scattering between relativistic particles and the cosmic microwave background photons, the intracluster magnetic field B is limited to be > 0.03 mu G (HXD) and > 0.10 mu G (XIS).

The broad-band 1-300 keV Suzaku spectrum of IGR J17497-2821, the X-ray transient discovered by INTEGRAL in 2006 September, is presented. Suzaku observed IGR J17497-2821 on September 25, eight days after its discovery, for a net exposure of about 53 ks. During the Suzaku observation, IGR J17497-2821 is very bright, 2 x 10(37) erg s(-1) at 8 kpc in the 1-300 keV range, and shows a hard spectrum, typical of black hole candidates in the low-hard state. Despite the multi-mission X-ray monitoring of the source, only with Suzaku is it possible to obtain a broad-band spectrum in the 1-300 keV range with a very high signal to noise ratio. A sum of a multi-color disc and a thermal Comptonization component with mild reflection is a good representation of our IGR J17497-2821 Suzaku spectrum. The spectral properties of the accretion disc as well as the cut-off energy in the spectrum at about 150 keV are clearly detected and constrained. We discuss the implications on the physical model used to interpret the data and the comparison with previous results.

The Soft Gamma-ray Detector (SGD) on board ASTRO-H (Japanese next high-energy astrophysics mission) is a Compton telescope with narrow field-of-view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (50-600 keV) at a background level 10 times better than that of the Suzaku Hard X-ray Detector, and is complimentary to the Hard X-ray Imager on board ASTRO-H with an energy coverage of 5-80 keV. Excellent energy resolution is the key feature of the SGD, allowing it to achieve good background rejection capability taking advantage of good angular resolution. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of gamma-ray emission processes. Here we describe the instrument design of the SGD, its expected performance, and its development status. ©2009 IEEE.

The Soft Gamma-ray Detector (SGD) on board ASTRO-H (Japanese next high-energy astrophysics mission) is a Compton telescope with narrow field-of-view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (50-600 keV) at a background level 10 times better than that of the Suzaku Hard X-ray Detector, and is complimentary to the Hard X-ray Imager on board ASTRO-H with an energy coverage of 5-80 keV. Excellent energy resolution is the key feature of the SGD, allowing it to achieve good background rejection capability taking advantage of good angular resolution. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of gamma-ray emission processes. Here we describe the instrument design of the SGD, its expected performance, and its development status.

The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA sounding rocket mission which will study particle acceleration and coronal heating on the Sun through unprecedented high-resolution imaging in the hard X-ray energy band (5-15 keV). Energy release occurring in the quiet region of the Sun may potentially play an important role in the coronal heating mechanism. With a combination of high-resolution focusing Xray optics and fine-pitch imaging sensors, FOXSI will achieve superior sensitivity two orders of magnitude better than that of the RHESSI satellite. FOXSI requires the spectral capability down to 5 keV, which requires a development of a new ASIC and detector with a better energy resolution. We plan to use a Doublesided Si Strip Detector (DSSD) with a low-noise front-end ASIC as the FOXSI focal plane detector, which will fulfill the scientific requirements on the spatial resolution, energy resolution, lower threshold energy and time resolution. We have designed and fabricated a DSSD with a thickness of 500 μm and a dimension of 9.6 mmx9.6 mm, containing 128 strips separated by a pitch of 75 μm, which corresponds to 8 arcsec at the focal length of 2 m. The DSSD was successfully operated in a laboratory experiment. Under a temperature of 20 °C and a bias voltage of 250 V, we obtained spectra from both sides of the electrodes. The energy resolution was measured to be 980 eV and 2.4 keV for the pside and n-side at 14 keV gamma-ray, sufficient for the FOXSI mission requirement. ©2009 IEEE.

The Focusing Optics x-ray Solar Imager (FOXSI) is a sounding rocket payload funded under the NASA Low Cost Access to Space program to test hard x-ray focusing optics and position-sensitive solid state detectors for solar observations. Today's leading solar hard x-ray instrument, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) provides excellent spatial (2 arcseconds) and spectral (1 keV) resolution. Yet, due to its use of indirect imaging, the derived images have a low dynamic range (< 30) and sensitivity. These limitations make it difficult to study faint x-ray sources in the solar corona which are crucial for understanding the solar flare acceleration process. Grazing-incidence x-ray focusing optics combined with position-sensitive solid state detectors can overcome both of these limitations enabling the next breakthrough in understanding particle acceleration in solar flares. The FOXSI project is led by the Space Science Laboratory at the University of California. The NASA Marshall Space Flight Center, with experience from the HERO balloon project, is responsible for the grazing-incidence optics, while the Astro H team (JAXA/ISAS) will provide double-sided silicon strip detectors. FOXSI will be a pathfinder for the next generation of solar hard x-ray spectroscopic imagers. Such observatories will be able to image the non-thermal electrons within the solar flare acceleration region, trace their paths through the corona, and provide essential quantitative measurements such as energy spectra, density, and energy content in accelerated electrons.

We present results obtained from a series of observations of the supernova remnant RX J1713.7-3946 by Suzaku. Hard X-rays have been detected up to similar to 40 keV. The hard X-ray spectra are described by a power law with photon indices of similar to 3.0, which is larger than those below 10 keV. The combination of the spatially integrated XIS and HXD spectra clearly reveals a spectral cutoff which is linked to the maximum energy of accelerated electrons. The broad-band coverage of Suzaku allows us to derive, for the first time, the energy spectrum of parent electrons in the cutoff region. The cutoff energy in the X-ray spectrum indicates that the electron acceleration in the remnant proceeds close to the Bohm diffusion limit. We discuss the implications of the spectral and morphological properties of the Suzaku data in the context of the origin of nonthermal emission. The Suzaku X-ray and H.E.S.S. gamma-ray data together hardly can be explained within a pure leptonic scenario. Moreover, the leptonic models require a weak magnetic field, which is inconsistent with the recently discovered X-ray filamentary structures and their short-term variability. The hadronic models with strong magnetic fields provide reasonable fits to the observed spectra, but require special arrangements of parameters to explain the lack of thermal X-ray emission. For morphology studies, we compare the X-ray and TeV gamma-ray surface brightness. We confirm the previously reported strong correlation between X-rays and TeV gamma rays. At the same time, the Suzaku data reveal a deviation from the general tendency, namely, the X-ray emission in the western rims appears brighter than expected from the average X-ray to gamma-ray ratio.

A digital processing system for a TES microcalorimeter array is being developed based on "SpaceWire" interface. In this system, we introduced a trigger logic which can handle double-pulse events due to high count rate in future X-ray missions and several application on the ground experiments. The detailed design and performance of this system is described.

A Suzaku TOO observation of CXOU J164710.2-455216 was performed on 2006 September 23-24 for a net exposure of 38.8 ks. Pulsations were clearly detected in the XIS light curves with a pulse period of 10.61063(2) s. The XIS pulse profile is found to be highly non-sinusoidal. It shows 3 peaks of different amplitudes with an RMS fractional amplitude of similar to 11% in the 0.2-6.0 keV energy band. The 1 -10 keV XIS spectra were well fitted by two different models consisting of a power-law and a blackbody component and two blackbody components, respectively. Although both the models are statistically acceptable, a difference in the pulse profiles at soft (0.2-6.0 keV) and hard (6-12keV) X-rays favors the model consisting of two blackbody components. The temperatures of two blackbody components are found to be 0.61 +/- 0.01 keV and 1.22 +/- 0.06 keV, and the value of the absorption column density is 1.73 +/- 0.03 x 10(22) atoms cm(-2). Pulse phase resolved spectroscopy shows that the flux of the soft blackbody component consists of three narrow peaks, whereas the flux of the other component shows a single peak over the pulse period of the AXP. The blackbody radii change between 2.2-2.7 km and 0.28-0.38 km (assuming the source distance to be 5 kpc) over the pulse phases for the soft and hard components, respectively. The details of the results obtained from the timing and spectral analyses are presented.

The accretion-powered pulsar Her X-1 was observed with Suzaku twice in its main-on state, on 2005 October 5-6 and 2006 March 29-30, for a net exposure of 30.5 ks and 34.4 ks, respectively. In the 2005 and 2006 observations, the source was detected at an average 10-30 keV intensity of 290 mCrab and 230 mCrab, respectively. The intrinsic pulse period was measured on both occasions at 1.23776 s by HXD-PIN, after barycentric and binary corrections. The pulse phase-averaged spectra in the energy range above 10 keV were well fitted by the "Negative and Positive power-law times EXponential" (NPEX) model, multiplied by a fundamental cyclotron resonance scattering feature at similar to 36 keV, which appears very significantly in the HXD-PIN data. The resonance profiles were successfully reproduced by a Lorentzian-type scattering cross section, rather than by a Gaussian-type alternative. The pulse phase-averaged HXD-GSO data, covering 50-120 keV, are featureless. However, in a differential spectrum between the pulse-decay phase and off-pulse phase, the second-harmonic cyclotron resonance was detected in the GSO data at similar to 73 keV, with a depth of 1.6(-0.7)(+0.9) This makes Her X-1 a 6th pulsar with established second-harmonic resonance. The implications of these results are briefly discussed.

We report on the wide-band spectra of SN 1006, as observed by Suzaku. Thermal and nonthermal emissions were successfully resolved thanks to the excellent spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission could not be reproduced by a simple power-law model, but needed a roll-off at 5.7 x 10(16) Hz = 0.23 keV. The roll-off frequency is significantly higher in the northeastern rim than in the southwestern rim. We also placed the most stringent upper limit of the flux above 10 keV using the Hard X-ray Detector.

Five on-plane regions within +/-0.degrees 8 of the galactic center were observed with the Hard X-ray Detector (HXD) and the X-ray Imaging Spectrometer (XIS) aboard Suzaku. From all regions, significant hard X-ray emission was detected with HXD-PIN up to 40 keV, in addition to the extended plasma emission which is dominant in the XIS band. The hard X-ray signals are inferred to come primarily from a spatially extended source, rather than from a small number of bright discrete objects. Contributions to the HXD data from catalogued X-ray sources, typically brighter than 1 mCrab, were estimated and removed using information from Suzaku and other satellites. Even after this removal, the hard X-ray signals remained significant, exhibiting a typical 12-40keV surface brightness of 4 x 10(-10) erg cm(-2) s(-1) deg(-2) and power-law-like spectra with a photon index of 1.8. Combined fittings to the XIS and HXD-PIN spectra confirm that a separate hard tail component is superposed onto the hot thermal emission, confirming a previous report based on the XIS data. Over the 5-40 keV band, the hard tail is spectrally approximated by a power law of photon index similar to 2, but better by those with somewhat convex shapes. Possible origins of the extended hard X-ray emission are discussed.

We present observations of the North Polar Spur (NPS) using the X-ray Imaging Spectrometer (XIS) aboard the Suzaku X-ray satellite. The NPS is a large region of enhanced soft X-ray and radio emission projected above the plane of the Galaxy, likely produced by a series of supernovae and stellar winds from the nearby Sco-Cen OB association. The exceptional sensitivity and spectral resolution of the XIS below 1 keV allow unprecedented probing of low-energy spectral lines, including C VI (0.37 keV) and N VII (0.50 keV), and we have detected highly-ionized nitrogen toward the NPS for the first time. For this single pointing toward the brightest 3/4 keV emission (l = 26.degrees 8, b = +22.degrees 0), the best-fit NPS emission model implies a hot (kT approximate to 0.3 keV), collisional ionization equilibrium (CIE) plasma with depleted C, O, Ne, Mg, and Fe abundances of less than 0.5 solar, but an enhanced N abundance, with N/O = (4.0(-0.5)(+0.4)) times solar. The temperature and total thermal energy of the gas suggest heating by one or more supernovae, while the enhanced nitrogen abundance is best explained by enrichment from stellar material that has been processed by the CNO cycle. Due to the time required to develop AGB stars, we conclude that this N/O enhancement cannot be caused by the Sco-Cen OB association, but may result from a previous enrichment episode in the solar neighborhood.

The Galactic black-hole binary GROJ1655-40, a source harboring superluminal jets, was observed with Suzaku on 2005 September 22-23. The source was detected over a broad and continuous energy range of 0.7-300 keV, with an intensity of similar to 50 mCrab at 20 keV At a distance of 3.2 kpc, the 0.7-300 keV luminosity was similar to 5.2 x 10(36) erg s(-1) (similar to 0.7% of the Eddington luminosity for a 6 M-circle dot black hole). The source was in a typical low/hard state, exhibiting a power-law shaped continuum with a photon index of similar to 1.6. During the observation, the source intensity gradually decreased by 25% at energies above similar to 3 keV, and by 35% below 2 keV. This, together with the soft X-ray spectra taken with the X-ray Imaging Spectrometer (XIS), suggests the presence of an independent soft component that can be represented by emission from a cool (similar to 0.2 keV) disk. The hard X-ray spectra obtained with the Hard X-ray Detector reveal a high-energy spectral cutoff, with an e-folding energy of similar to 200 keV. The entire 0.7-300 keV spectrum cannot be reproduced by a single thermal Comptonization model, even when considering reflection effects. Instead, the spectrum (except the soft excess) can be successfully explained by invoking two thermal-Comptonization components with different y-parameters. In contrast to the high/soft state spectra of this object, in which narrow iron absorption lines are detected with equivalent widths of 60-100 eV, the present XIS spectra bear no such features beyond an upper-limit equivalent width of 23 eV.

In order to carry out a precise spectral study of the Galactic Ridge X-ray Emission using Suzaku, we have observed a typical Galactic plane field at (l, b) = (28 degrees 46, -0 degrees 20), which is already deeply observed with Chandra, and known to be devoid of bright X-ray point sources. Thanks to the low background and high spectral resolution of Suzaku, we were able to resolve three narrow iron K-emission lines from low-ionized (6.41 keV), helium-like (6.67 keV), and hydrogenic ions (7.00 keV). The cosmic-ray ion charge-exchange model or the non-equilibrium ionization plasma model are unlikely to explain these line features, since they require either broad emission lines or lines at intermediate ionization states. Collisional ionization equilibrium plasma is the likely origin for the 6.67 keV and 7.00 keV lines; however, the origin of the 6.41 keV line, which is due to fluorescence from cold material, has not been elucidated. We could also precisely measure the absolute X-ray surface brightness in the direction of the Galactic plane. Excluding point sources brighter than similar to 2 X 10(-13) erg s(-1) cm(-2) (2-10keV), the total surface brightness on the Galactic plane is similar to 6.1 x 10(-11) erg s(-1) cm(-2) deg(-2) (2-10keV), including the contribution of the cosmic X-ray background, which is estimated to be similar to 1.3 x 10(-11) erg s(-1) cm(-2) deg(-2).

The hard X-ray detector (HXD) aboard the X-ray satellite Suzaku is designed to have a good timing capability with a 61 its time resolution. In addition to detailed descriptions of the HXD timing system, results of in-orbit timing calibration and the performance of the HXD are summarized. The relative accuracy of time measurements of the HXD event was confirmed to have an accuracy of 1.9 x 10(-9) s s(-1) per day, and the absolute timing was confirmed to be accurate to 360 mu s or better. The results were achieved mainly through observations of the Crab pulsar, including simultaneous ones with RXTE, INTEGRAL, and Swift.

We report on results from Suzaku broadband X-ray observations of the southwest part of the galactic supernova remnant (SNR) RX J1713.7-3946 with an energy coverage of 0.4-40keV. The X-ray spectrum, presumably of synchrotron origin, is known to be completely lineless, making this SNR ideally suited for a detailed study of the X-ray spectral shape formed through efficient particle acceleration at high-speed shocks. With a sensitive hard X-ray measurement from the HXD PIN aboard Suzaku, we determined the hard X-ray spectrum in the 12-40 keV range to be described by a power law with photon index of Gamma = 3.2 +/- 0.2, significantly steeper than the soft X-ray index of Gamma = 2.4 +/- 0.05 measured previously with ASCA and other missions. We find that a simple power law fails to describe the full spectral range of 0.4-40 keV, and instead a power-law with an exponential cutoff with a hard index of Gamma = 1.50 +/- 0.09 and a high-energy cutoff of epsilon(c) = 1.2 +/- 0.3 keV formally provides an excellent fit over the full bandpass. If we use the so-called SRCUT model, as an alternative model, it gives a best-fit rolloff energy of epsilon(roll) = 0.95 +/- 0.04 keV. Together with the TeV gamma-ray spectrum, ranging from 0.3 to 100 TeV, recently obtained by HESS observations, our Suzaku observations of RX J1713.7-3946 provide stringent constraints on the highest-energy particles accelerated in a supernova shock.

The Hard X-ray Imager (HXI) is one of three focal plane detectors on board the NeXT (New exploration X-ray Telescope) mission, which is scheduled to be launched in 2013. By use of the hybrid structure composed of double-sided silicon strip detectors and a cadmium telluride strip detector, it fully covers the energy range of photons collected with the hard X-ray telescope up to 80 keV with a high quantum efficiency. High spatial resolutions of 400 micron pitch and energy resolutions of 1-2 keV (FWMH) are at the same time achieved with low noise front-end ASICs. In addition, thick BGO active shields compactly surrounding the main detection part, as a heritage of the successful performance of the Hard X-ray Detector (HXD) on board Suzaku satellite, enable to achive an extremely high background reduction for the cosmic-ray particle background and in-orbit activation. The current status of hardware development including the design requirement, expected performance, and technical readinesses of key technologies are summarized.

We report on the observational results of GRBs by the Suzaku Wide-band All-sky Monitor (WAM) in these two years since the Suzaku launch. Using the WAM data, we can investigate the spectral properties of the prompt emission of GRBs with a wider energy band and the highest sensitivity than any previous GRB missions. We found that the spectral properties between short and long GRBs, such as the spectral parameter distribution, the hardness ratio, the spectral lag, and the total emitting energy are clearly different even in the MeV energy band. This result implies that different progenitors or different bulk Lorentz factors of the ejecta are likely causes for the difference between these two classes. We also found that there is a strong correlation between the peak energy and the isotropic equivalent luminosity of the time-resolved spectra of the bright long GRB 061007, and found that this correlation can be separated well between rising and decay phase of each pulse. This indicates that the physical condition changes during the pulse phase of the burst.

The Hard X-ray Imager (HXI) is one of three focal plane detectors on board the NeXT (New exploration X-ray Telescope) mission, which is scheduled to be launched in 2013. By use of the hybrid structure composed of double-sided silicon strip detectors and a cadmium telluride strip detector, it fully covers the energy range of photons collected with the hard X-ray telescope up to 80 keV with a high quantum efficiency. High spatial resolutions of 400 micron pitch and energy resolutions of 1-2 keV (FWMH) are at the same time achieved with low noise front-end ASICs. In addition, thick BGO active shields compactly surrounding the main detection part, as a heritage of the successful performance of the Hard X-ray Detector (HXD) on board Suzaku satellite, enable to achive an extremely high background reduction for the cosmic-ray particle background and in-orbit activation. The current status of hardware development including the design requirement, expected performance, and technical readinesses of key technologies are summarized.

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

The Hard X-ray Imager (HXI) is one of three focal plane detectors on board the NeXT (New exploration X-ray Telescope) mission, which is scheduled to be launched in 2013. By use of the hybrid structure composed of double-sided silicon strip detectors and a cadmium telluride strip detector, it fully covers the energy range of photons collected with the hard X-ray telescope up to 80 keV with a high quantum efficiency. High spatial resolutions of 400 micron pitch and energy resolutions of 1-2 keV (FWMH) are at the same time achieved with low noise front-end ASICs. In addition, thick BGO active shields compactly surrounding the main detection part, as a heritage of the successful performance of the Hard X-ray Detector (HXD) on board Suzaku satellite, enable to achive an extremely high background reduction for the cosmic-ray particle background and in-orbit activation. The current status of hardware development including the design requirement, expected performance, and technical readinesses of key technologies are summarized.

XEUS mission has been considered as an international X-ray observatory in 2015-25 time frame, by X-ray astronomers in Europe and Japan from late 1990's. The original idea was the exploration of the first generation of blackholes in the early Universe with a huge X-ray telescope. In the new century, for key science cases of space programs, Cosmic Vision 2015-2015 were discussed and summarized as follows.

The Wide-band All-sky Monitor (WAM) is a made up of the large lateral BGO shield of the Hard X-ray Detector (HXD) onboard Suzaku. Its large geometrical area of 800 cm(2) per side, the large stopping power for the hard X-rays and the wide-field of view make the WAM an ideal detector for gamma-ray bursts (GRBs) observations in the energy range of 50-5000 keV In fact, the WAM has observed 288 GRBs confirmed by other satellites, till the end of May 2007.

We have developed a Compton camera with a double-sided silicon strip detector (DSSD) for hard X-ray and gamma-ray observation. Using a DSSD as a scatter detector of the Compton camera., we achieved high angular resolution of 3.4 at 511 keV. Through the imaging of various samples such as two-dimentional array sources and a diffuse source, the wide field-of-view (similar to 100 degrees) and the high spatial resolution (at; least 20 mm at a distance; of 60 mm from the DSSD) of the camera were confirmed. Furthermore, using the List; Mode Maximum-Likelihood Expectation-Maximization method, the camera can resolve ail interval of 3 mm at a distance of 30 mm from the DSSD.

The NeXT (New exploration X-ray Telescope). the new Japanese X-ray Astronomy Satellite following Suzaku, is all international X-ray mission which is currently planed for launch in 2013. NeXT is a combination of wide band X-ray spectroscopy (3-80 keV) provided by multi-layer coating, focusing hard X-ray mirror and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-10 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft, X-ray telescope and a non-focusing soft, gamma-ray detector. With these instruments, NeXT Covers very wide energy range from 0.3 keV to 600 keV. The micro-calorimeter system will be developed by international collaboration lead ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of Delta E similar to 7 eV by the micro-calorimeter will enable a wide variety of important, science themes to be pursued.

A report is made on a comprehensive observation of a burstlike gamma-ray emission from thunderclouds on the Sea of Japan, during strong thunderstorms on 6 January 2007. The detected emission, lasting for similar to 40 sec, preceded cloud-to-ground lightning discharges. The burst spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung photons originating from relativistic electrons. This ground-based observation provides the first clear evidence that strong electric fields in thunderclouds can continuously accelerate electrons beyond 10 MeV prior to lightning discharges.

A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3-250 keV. The net exposure times after screening were 70 ks per X-ray Imaging Spectrometer (XIS) camera, 60.8 ks for the Hard X- ray Detector (HXD) PIN, and 17.1 ks for the HXD GSO. The hard X- rays are fit by two power laws of the same slope, absorbed by columns of 1.5 and 7 x 10(23) cm(-2), respectively. The spectrum is consistent with previous suggestions that the power-law components are X- ray emission from the subparsec VLBI jet and from Bondi accretion at the core, but it is also consistent with a partial-covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, jet emission, and emission from X- ray binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca, and Ni are detected. The Fe K proportional to line width yields a 200 lt-day lower limit on the distance from the black hole to the line-emitting gas. Fe, Ca, and S K-shell absorption edges are detected. Elemental abundances are constrained via absorption edge depths and strengths of the fluorescent and diffuse plasma emission lines. The high metallicity ([Fe/H] = +0.1) of the circumnuclear material suggests that it could not have originated in the relatively metal-poor outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

Based on our successful development of ceramic Y3Al5O12(Ce) scintillators, we fabricated two samples of (YGd)(3)Al5O12(Ce) scintillator, to achieve higher stopping power to gamma-rays. They are both activated with Ce to a 0.5 mol% concentration, but differ in sintering conditions. We investigated their optical properties and gamma-ray responses. One of them showed a poor (similar to 1%) optical transparency at 550 nm, while the other had a much improved (similar to 20%) transmission. They both showed a dominant decay constant of similar to 90 ns, when irradiated with gamma-rays. The more transparent one exhibited light yield which is similar to 30% of that of ceramic YAG(Ce), and similar to 14% (FWHM) energy resolution at 662 keV when coupled with a phototube. When coupled with an avalanche photo diode, it exhibited similar to 8% energy resolution at the same energy. The stopping power of the new ceramics was confirmed to be five times as high as that of YAG(Ce) at similar to 660keV, by counting detected photo-absorption events. (c) 2007 Elsevier B.V. All rights reserved.

Using Chandra, extended X-ray emission was detected from the direction of 6 globular clusters: 47 Tucanae, NGC 6752, M 5, omega Centauri, M 80, and NGC 6266. These X-ray sources, extending to a few arcmin, are located 1'-6' away from the cluster centers, and some are found in the direction of cluster motion through the Galactic halo. All of these sources are concluded to be diffuse, rather than an assembly of faint discrete X-ray sources. Those in 47 Tuc and NGC 6752 have similar spectra, described by a power law with a photon index of similar to 2, or a thin-thermal model with a temperature of similar to 3-4 keV. Furthermore, they both have 843 MHz radio counterparts. The diffuse emission from omega Cen exhibits a similar to 1.0 keV thermal spectrum, while that from M 5 shows an even softer (similar to 0.05 keV) spectrum. While the diffuse source in (o Cen could be a background contaminant, the others are likely to be physically associated with the globular clusters. Then, the absorption-corrected 0.5-4.5 keV luminosity of the sources in 47 Tuc and NGC 6752 becomes (3-6) x 10(32) erg s(-1). These results are discussed in the context of shocks produced by the cluster motion through the Galactic halo, and the associated gas heating and particle acceleration.

We carried out observations of the central and 20' east offset regions of the cluster of galaxies Abell 1060 with Suzaku. Spatially resolved X-ray spectral analysis has revealed temperature and abundance profiles of Abell 1060 out to 27' similar or equal to 380 h(70)(-1) kpc, which corresponds to similar to 0.25 r(180). Temperature decrease of the intra-cluster medium 70 from 3.4 keV at the center to 2.2 keV in the outskirt region was clearly observed. The abundances of Si, S, and Fe also decrease by more than 50% from the center to the outer region, while Mg shows a fairly constant abundance distribution at similar to 0.7 solar within r less than or similar to 17'. O shows a lower abundance of similar to 0.3 solar in the central region (r less than or similar to 6'), and indicates a similar feature with Mg; however, it is sensitive to the estimated contribution of the Galactic components of kT(1) similar to 0.15 keV and kT(2) similar to 0.7 keV in the outer annuli (r greater than or similar to 13'). Systematic effects due to the point-spread function tails, contamination on the XIS filters, instrumental background, cosmic and/or Galactic X-ray background, and the assumed solar abundance tables were carefully examined. The results on the temperature and abundances of Si, S, and Fe are consistent with those derived by XMM-Newton at r less than or similar to 13'. The formation and metal-enrichment process of the cluster are discussed based on the present results.

Double-sided silicon strip detectors (DSSD) with an energy resolution of 1-2 keV full-width at half-maximum (FWHM) are attractive devices for future hard X-ray and soft y-ray applications. For example, they are well suited as scatterer detectors for semiconductor Compton telescopes working in the sub-MeV to MeV band, as well as imaging spectrometers in the hard X-ray band. In this paper, the performance of newly developed 4-cm-wide DSSDs is presented. This DSSD has an active area of 38.4 mm times 38.4 mm, with a thickness of 300 mu m. The stip pitch is 400 mu m. The detector shows an average energy resolution of 1.5 keV (FWHM) for 59.5 keV gamma-rays, operated at -20 degrees C with a bias of 100V. A 22 keV hard X-ray image is also obtained with 400 mu m resolution. (c) 2006 Elsevier B.V. All rights reserved.

A summary is given on the timing accuracy verifications of the Hard X-ray Detector (HXD) on board the Suzaku satellite. Suzaku has so far observed several Xray pulsars, such as the Crab pulsar, PSR 1509-58, and A0535+26, partially for the purpose of calibrating the HXD timing accuracy and energy responses. Through standard barycentric corrections and temperature compensations of the oscilator in the central data processing unit, the relative and absolute timing accuracies were confirmed using the HXD data of the Crab pulsar. Some initial Suzaku results on X-ray pulsars are also presented.

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

Since the typical magnetic field strengths of neutron stars reach 1012 Gauss, the cyclotron resonance produced by a transition between Landau levels appears in the X-ray band. Systematic measurements of cyclotron absorption features in bright sources have been carried out extensively with Ginga, RXTE, BeppoSAX, and INTEGRAL. The cyclotron resonance phenomena can now be studied with a higher sensitivity over a wider hard X-ray band than before, thanks to the Hard X-ray Detector onboard the fifth Japanese X-ray satellite, Suzaku, launched in July, 2005. Suzaku observed Hercules X-1 mainly for calibration purposes, and successfully confirmed its well-known cyclotron absorption feature. Furthermore, the transient pulsar A0535+262 was observed with Suzaku on 14 September, 2005, in the decay phase of its minor outburst (Finger, M.F. Renewed Activity from A0535+26. The Astronomer's Telegram, vol. 595, 2005). The cyclotron resonance of A0535+262 was successfully detected in absorption at about 45 keV (Inoue, H., Kunieda, H., White, N., Kelley, R., Nlihara, T., Terada, Y., Takahashi, H., Kokubun, M., Makishima, K. Suzaku detection of cyclotron line near 50 keV for A0535+26. The Astronomer's Telegram vol. 595, 2005; Terada, Y., Mihara, T., Nakajima, M., et al. Cyclotron resonance energies at a low X-ray luminosity: A0535+262 observed with Suzaku. ApJL 648, L139-LI42, 2006), even though the object was as dim as 30 mCrab at 20 keV. Compared with previous measurements of the same feature achieved at much brighter phases (e.g., Kretschmar, P., Kreykenbohm, I., Pottschmidt, et al. Integral observes possible cyclotron line at 47 keV for 1A0535+262. The Astronomer's Telegram, vol. 601, 2005; Wilson, C.A., Finger, M.H. RXTE confirms cyclotron line near 50 keV for A0535+26. The Astronomer's Telegram 605, 2005), the Suzaku results give a new constraint to luminosity-related changes in the resonance energy that are observed in other binary pulsars (Nakajima, M., Mihara, T., Makishima, K., Niko, H. A further study of the luminosity-dependent cyclotron resonance energies of the binary X-ray pulsar 4U 0115+63 with the Rossi X-ray timing explorer. ApJ 646, 1125-1138, 2006). (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.