-
Tadayuki Takahashi,
Kazuhisa Mitsuda,
Richard Kelley,
Henri AartsFelix Aharonian,
Hiroki Akamatsu,
Fumie Akimoto,
Steve Allen,
Naohisa Anabuki,
Lorella Angelini,
Keith Arnaud, [......],
Takahiro Yamada,
Shinya Yamada,
Hiroya Yamaguchi,
Noriko Yamasaki,
Shigeo Yamauchi,
Makoto Yamauchi,
Yoichi Yatsu,
Daisuke Yonetoku,
Atsumasa Yoshida,
Takayuki Yuasa
[show abstract]
[hide abstract]
ABSTRACT: The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly
successful X-ray missions initiated by the Institute of Space and Astronautical
Science (ISAS). ASTRO-H will investigate the physics of the high-energy
universe via a suite of four instruments, covering a very wide energy range,
from 0.3 keV to 600 keV. These instruments include a high-resolution,
high-throughput spectrometer sensitive over 0.3-2 keV with high spectral
resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in
the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers
covering 5-80 keV, located in the focal plane of multilayer-coated, focusing
hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12
keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and
a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the
40-600 keV band. The simultaneous broad bandpass, coupled with high spectral
resolution, will enable the pursuit of a wide variety of important science
themes.
10/2012;
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Kirpal Nandra,
Didier Barret,
Andy Fabian,
Lothar Strueder,
Richard Willingale,
Mike Watson,
Peter Jonker, Hideyo Kunieda,
Giovanni Miniutti,
Christian Motch,
Peter Predehl
[show abstract]
[hide abstract]
ABSTRACT: GRAVITAS is an X-ray observatory, designed and optimised to address the ESA Cosmic Vision theme of “Matter under extreme conditions”.
It was submitted as a response to the call for M3 mission proposals. The concept centres around an X-ray telescope of unprecedented
effective area, which will focus radiation emitted from close to the event horizon of black holes or the surface of neutron
stars. To reveal the nature and behaviour of matter in the most extreme astrophysical environments, GRAVITAS targets a key
feature in the X-ray spectra of compact objects: the iron Kα line at ~6.5keV. The energy, profile, and variability of this emission line, and the properties of the surrounding continuum
emission, shaped by General Relativity (GR) effects, provide a unique probe of gravity in its strong field limit. Among its
prime targets are hundreds of supermassive black holes in bright Active Galactic Nuclei (AGN), which form the perfect laboratory
to help understand the physical processes behind black hole growth. Accretion plays a fundamental role in the shaping of galaxies
throughout cosmic time, via the process of feedback. Modest (~sub-arcmin) spatial resolution would deliver the necessary sensitivity
to extend high quality X-ray spectroscopy of AGN to cosmologically-relevant distances. Closer to home, ultra-high count rate
capabilities and sub-millisecond time resolution enable the study of GR effects and the equation of state of dense matter
in the brightest X-ray binaries in our own Galaxy, using multiple probes, such as the broad iron line, the shape of the disk
continuum emission, quasi-periodic oscillations, reverberation mapping, and X-ray burst oscillations. The enormous advance
in spectral and timing capability compared to current or planned X-ray observatories would enable a vast array of additional
scientific investigations, spanning the entire range of contemporary astrophysics from stars to distant galaxy clusters. Despite
its breakthrough capabilities, all enabling technologies for GRAVITAS are already in a high state of readiness. It is based
on ultra light-weight X-ray optics and a focal plane detector using silicon technology. The baseline launcher would be a Soyuz–Fregat
to place GRAVITAS into a zero inclination, low-earth orbit, providing low and relatively stable background.
KeywordsGRAVITAS–Soyuz–Fregat–X-ray optics–Silicon technology–ESA Cosmic Vision
Experimental Astronomy 04/2012; · 1.82 Impact Factor
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Monique Arnaud,
Xavier Barcons,
Didier Barret,
Marshall Bautz,
Ronaldo Bellazzini,
Johan Bleeker,
Hans Böhringer,
Thomas Boller,
William Nielsen Brandt,
Massimo Cappi, [......],
Tadayuki Takahashi,
Marc Türler,
Martin Turner,
Yoshihiro Ueda,
Cristian Vignali,
Jacco Vink,
Robert Warwick,
Mike Watson,
Richard Willingale,
Shuang Nan Zhang
[show abstract]
[hide abstract]
ABSTRACT: This paper describes the next generation X-ray observatory XEUS which has been submitted to the European Space Agency in the
framework of the Cosmic Vision 2015–2025 competition and has been selected for an assessment study. The paper summarizes the
scientific goals and instrumental concepts of the proposed X-ray telescope with 5m2 effective area and angular resolution better than 5arc sec.
Experimental Astronomy 04/2012; 23(1):139-168. · 1.82 Impact Factor
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Kirpal Nandra,
Didier Barret,
Andy Fabian,
Lothar Strueder,
Richard Willingale,
Mike Watson,
Peter Jonker, Hideyo Kunieda,
Giovanni Miniutti,
Christian Motch,
Peter Predehl,
on behalf of the former GRAVITAS consortium
[show abstract]
[hide abstract]
ABSTRACT: GRAVITAS is an X-ray observatory, designed and optimised to address the ESA
Cosmic Vision theme of "Matter under extreme conditions". It was submitted as a
response to the call for M3 mission proposals. The concept centres around an
X-ray telescope of unprecedented effective area, which will focus radiation
emitted from close to the event horizon of black holes or the surface of
neutron stars. To reveal the nature and behaviour of matter in the most extreme
astrophysical environments, GRAVITAS targets a key feature in the X-ray spectra
of compact objects: the iron Kalpha line at ~6.5 keV. The energy, profile, and
variability of this emission line, and the properties of the surrounding
continuum emission, shaped by General Relativity (GR) effects, provide a unique
probe of gravity in its strong field limit. Among its prime targets are
hundreds of supermassive black holes in bright Active Galactic Nuclei (AGN),
which form the perfect laboratory to help understand the physical processes
behind black hole growth. Accretion plays a fundamental role in the shaping of
galaxies throughout cosmic time, via the process of feedback. Modest
(~sub-arcmin) spatial resolution would deliver the necessary sensitivity to
extend high quality X-ray spectroscopy of AGN to cosmologically-relevant
distances. Closer to home, ultra-high count rate capabilities and
sub-millisecond time resolution enable the study of GR effects and the equation
of state of dense matter in the brightest X-ray binaries in our own Galaxy,
using multiple probes, such as the broad iron line, the shape of the disk
continuum emission, quasi-periodic oscillations, reverberation mapping, and
X-ray burst oscillations. Despite its breakthrough capabilities, all enabling
technologies for GRAVITAS are already in a high state of readiness. It is based
on ultra light-weight X-ray optics and a focal plane detector using silicon
technology.
07/2011;
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Asami Hayato,
Hiroya Yamaguchi,
Toru Tamagawa,
Satoru Katsuda,
Una Hwang,
John P. Hughes,
Midori Ozawa,
Aya Bamba,
Kenzo Kinugasa,
Yukikatsu Terada,
Akihiro Furuzawa, Hideyo Kunieda,
and Kazuo Makishima
[show abstract]
[hide abstract]
ABSTRACT: We show that the expansion of ejecta in Tycho's supernova remnant (SNR) is consistent with a spherically symmetric shell, based on Suzaku measurements of the Doppler broadened X-ray emission lines. All of the strong Kα line emissions show broader widths at the center than at the rim, while the centroid energies are constant across the remnant (except for Ca). This is the pattern expected for Doppler broadening due to expansion of the SNR ejecta in a spherical shell. To determine the expansion velocities of the ejecta, we applied a model for each emission-line feature having two Gaussian components separately representing red- and blueshifted gas, and inferred the Doppler velocity difference between these two components directly from the fitted centroid energy difference. Taking into account the effect of projecting a three-dimensional shell to the plane of the detector, we derived average spherical expansion velocities independently for the Kα emission of Si, S, Ar, and Fe, and Kβ of Si. We found that the expansion velocities of Si, S, and Ar ejecta of 4700 ± 100 km s–1 are distinctly higher than that obtained from Fe Kα emission, 4000 ± 300 km s–1, which is consistent with segregation of the Fe in the inner ejecta. Combining the observed ejecta velocities with the ejecta proper-motion measurements by Chandra, we derived a distance to Tycho's SNR of 4 ± 1 kpc.
The Astrophysical Journal 11/2010; 725(1):894. · 6.02 Impact Factor
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Tadayuki Takahashi,
Kazuhisa Mitsuda,
Richard Kelley,
Felix Aharonian,
Fumie Akimoto,
Steve Allen,
Naohisa Anabuki,
Lorella Angelini,
Keith Arnaud,
Hisamitsu Awaki, [......],
Nicholas White,
Takahiro Yamada,
Hiroya Yamaguchi,
Kazutaka Yamaoka,
Noriko Yamasaki,
Makoto Yamauchi,
Shigeo Yamauchi,
Yoichi Yatsu,
Daisuke Yonetoku,
Atsumasa Yoshida
[show abstract]
[hide abstract]
ABSTRACT: The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe by performing high-resolution, high-throughput spectroscopy with moderate angular resolution. ASTRO-H covers very wide energy range from 0.3 keV to 600 keV. ASTRO-H allows a combination of wide band X-ray spectroscopy (5-80 keV) provided by multilayer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-12 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 (0.4-12 keV) and a non-focusing soft gamma-ray detector (40-600 keV) . The micro-calorimeter system is developed by an international collaboration led by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of Delta E ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued. Comment: 18 pages, 12 figures, Proceedings of the SPIE Astronomical Instrumentation "Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray"
10/2010;
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[show abstract]
[hide abstract]
ABSTRACT: Aims: We investigate the spatial distribution of dust emission around Tycho's SNR to understand its origin. We distinguish the dust associated with the SNR from that of the surrounding ISM. Methods: We performed mid- to far-infrared imaging observations of the remnant at wavelengths of 9, 15, 18, 24, 65, 90, 140, and 160um using the Infrared Camera and the Far-Infrared Surveyor onboard AKARI. We compared the AKARI images with the Suzaku X-ray image and the 12CO image of Tycho's SNR. Results: All the AKARI images except the 9, 140, and 160um band images show a shell-like emission structure with brightness peaks at the north east (NE) and north west (NW) boundaries, sharply outlining part of the X-ray shell. The 140 and 160um bands are dominated by cold dust emission from the surrounding ISM near the NE boundary. Conclusion: We conclude that the dust emission at the NE boundary comes from the ambient cloud interacting with the shock front, while the origin of the dust emission at the NW boundary is rather unclear because of the absence of prominent interstellar clouds near the corresponding region. We cannot rule out the possibility that the latter is mostly of an SN ejecta origin. Comment: Accepted for publication in A&A letter
09/2010;
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[show abstract]
[hide abstract]
ABSTRACT: The International X-ray Observatory (IXO) is a joint ESA-JAXA-NASA effort to address fundamental and timely questions in astrophysics: What happens close to a black hole? How did supermassive black holes grow? How does large scale structure form? What is the connection between these processes? To address these questions IXO will employ optics with 3 sq m collecting area and 5 arc sec angular resolution - 20 times more collecting area at 1 keV than any previous X-ray observatory. Focal plane instruments will deliver a 100-fold increase in effective area for high-resolution spectroscopy, deep spectral imaging over a wide field of view, unprecedented polarimetric sensitivity, microsecond spectroscopic timing, and high count rate capability. The mission is being planned for launch in 2021 to an L2 orbit, with a five-year lifetime and consumables for 10 years. Comment: 6 pages, 3 figures, for conference "X-ray Astronomy 2009 Present status, multi-wavelength approach and future perspectives"
01/2010;
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Akihiro Furuzawa,
Daisuke Ueno,
Asami Hayato,
Midori Ozawa,
Toru Tamagawa,
Aya Bamba,
John P. Hughes, Hideyo Kunieda,
Kazuo Makishima,
Stephen S. Holt,
Una Hwang,
Kenzo Kinugasa,
Robert Petre,
Keisuke Tamura,
Hiroshi Tsunemi,
and Shigeo Yamauchi
[show abstract]
[hide abstract]
ABSTRACT: We use Suzaku observations to measure the spatial variation of the Fe Kα line with radius in the Tycho supernova remnant. The Fe line widths show a significant decrease from a FWHM value of 210 eV at the center to 130 eV at the rim. Over the same radial range the line center energy remains nearly constant. These observations are consistent with a scenario in which the shell of Fe-emitting ejecta in Tycho is expanding at speeds of 2800-3350 km s–1. The minimum line width we measure is still a factor of two larger than expected from a single component plasma emission model. If thermal Doppler broadening is the dominant additional source of broadening, we infer an ion temperature of (1-3) × 1010 K.
The Astrophysical Journal 02/2009; 693(2):L61. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The new AM Her-type object AX J2315-592 was discovered with ASCA during the observation of IRAS 23128-5919. The light curve shows a clear periodic modulation at 1.489 ± 0.013 hr. Follow-up phase-resolved optical spectroscopy confirmed coincidence of the rotational period of the white dwarf and the orbital period and identified AX J2315-592 as a new AM Her-type object. The shape of the X-ray light curve is quasi-sinusoidal, the amplitude of which decreases with increasing X-ray energy, which is the property of intermediate polars. The X-ray emission at the maximum of the folded light curve has an optically thin thermal plasma emission spectrum with a temperature of 17 ± 4 keV with negligible absorption. The spectrum at the minimum, on the other hand, suffers from complex absorption. The X-ray light curve and the spectral characteristics indicate that a single accreting pole is always within the visible hemisphere of the white dwarf, and the rotational minimum occurs when the pole points toward the observer.
The Astrophysical Journal 01/2009; 470(1):L53. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present the results of an ASCA observation of the LINER NGC 4579. A pointlike X-ray source is detected at the nucleus with a 2-10 keV luminosity of 1.5 × 1041 ergs s-1 assuming a distance of 16.8 Mpc. The X-ray spectrum is represented by a combination of a power law with a photon index of ~1.7 and a soft thermal component with kT ~ 0.9 keV. An iron K emission line is detected at 6.73 ± 0.13 keV (rest-frame) with an equivalent width of 490−190+180 eV, and it is statistically significant at greater than 99.9% confidence. The line center energy is consistent with helium-like iron and is significantly higher than 6.4 keV, which is expected from fluorescence by "cold" (or a lower ionization state of) iron. The iron line profile shows no significant red tail in contrast to Seyfert 1 galaxies, although the statistics are limited. The line center energy, the equivalent width, and the profile are consistent with an origin in an ionized accretion disk. However, the large mass accretion rate necessary to ionize the accretion disk is not consistent with the observed luminosity and the normal accretion models.
The Astrophysical Journal 01/2009; 503(1):212. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Low-luminosity active galactic nuclei (AGNs), of which NGC 4639 is a good example, constitute an important but poorly understood constituent of the nearby galaxy population. We obtained observations of NGC 4639 with ASCA in order to investigate its mildly active Seyfert 1 nucleus at hard X-ray energies. Koratkar et al. have previously shown that the nucleus is a pointlike source in the ROSAT soft X-ray band. We detected in the 2-10 keV band a compact central source with a luminosity of 8.3 × 1040 ergs s-1 (for an adopted distance of 25.1 Mpc). Comparison of the ASCA data with archival data taken with the Einstein and ROSAT satellites shows that the nucleus varies on timescales of months to years. The variability could be intrinsic, or it could be caused by variable absorption. More rapid variability, on a timescale of ~104 s, may be present in the ASCA data. The spectrum from 0.5 to 10 keV is well described by a model consisting of a lightly absorbed (NH = 7.3 × 1020 cm-2) power law with a photon index of Γ = 1.68 ± 0.12. We find no evidence for significant emission from a thermal plasma; if present, it can account for no more than ~25% of the flux in the 0.5-2.0 keV band. The limited photon statistics of our data do not allow us to place significant limits on the presence of iron K emission. Despite its low luminosity, the X-ray properties of the nucleus of NGC 4639 appear quite normal compared with those of more luminous AGNs. The strength of its broad Hα line follows the correlation between broad Hα luminosity and hard X-ray luminosity that was previously known for luminous objects. Images taken with the Hubble Space Telescope detected the nucleus in the ultraviolet at a strength relative to the X-ray band that appears to be quite typical of that found in other AGNs. NGC 5033, another low-luminosity Seyfert 1 galaxy with optical characteristics that closely resemble those of NGC 4639, has also been studied recently with ASCA, and we highlight some of the similarities between these two objects.
The Astrophysical Journal 01/2009; 525(1):168. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present results of new ASCA observations of the low-luminosity active galactic nucleus (LLAGN) NGC 4579 obtained on 1998 December 18 and 28, and we report on the detection of variability of an iron K emission line. The X-ray luminosities in the 2-10 keV band for the two observations are nearly identical (LX ≈ 2 × 1041 ergs s-1), but they are ~35% larger than that measured in 1995 July by Terashima et al. An Fe K emission line is detected at 6.39 ± 0.09 keV (source rest frame), which is lower than the line energy 6.73 keV in the 1995 observation. If we fit the Fe lines with a blend of two Gaussians centered at 6.39 and 6.73 keV, the intensity of the 6.7 keV line decreases, while the intensity of the 6.4 keV line increases, within an interval of 3.5 yr. This variability rules out thermal plasmas in the host galaxy as the origin of the ionized Fe line in this LLAGN. The detection and variability of the 6.4 keV line indicates that cold matter subtends a large solid angle viewed from the nucleus and that it is located within ~1 pc from the nucleus. It could be identified with an optically thick standard accretion disk. If this is the case, a standard accretion disk is present at the Eddington ratio of Lbol/LEdd ~ 2 × 10-3. A broad disk-line profile is not clearly seen, and the structure of the innermost part of accretion disk remains unclear.
The Astrophysical Journal 12/2008; 535(2):L79. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: MACHO-96-BLG-5 was a microlensing event of exceptionally long duration, lasting ~800 days, which is suggestive of a stellar-mass black hole for the lens. With a 9.8 ks Chandra ACIS-S observation, we detected no X-ray events associated with the position of MACHO-96-BLG-5. An upper limit is estimated as 4.6 counts at the 99% confidence level. By assuming an absorbed power law spectrum with a photon index Γ = 1.4-2.0, the upper limit on the 0.3-8 keV luminosity is estimated as (7-8) × 1029 ergs s-1 at an assumed distance of 1 kpc. The corresponding Eddington ratio is (8-9) × 10-10 for a black hole of 6 M☉. The luminosity is lower than observed for quiescent black hole binaries in our Galaxy and is consistent with a scenario, previously suggested by Bennett et al., in which the lens for MACHO-96-BLG-5 is an isolated stellar-mass black hole, although other possibilities are not ruled out.
The Astrophysical Journal 12/2008; 631(1):L65. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The results from Suzaku XIS observations of the relaxed cluster of galaxies Abell2052 are presented. Offset pointing data are used to estimate the Galactic foreground emission in the direction to the cluster. Significant soft X-ray excess emission above this foreground, the intra-cluster medium emission, and other background components is confirmed and resolved spectroscopically and radially. This excess can be described either by (a) local variations of known Galactic emission components or (b) an additional thermal component with temperature of about 0.2 keV, possibly associated with the cluster. The radial temperature and metal abundance profiles of the intra-cluster medium are measured within \sim 20 in radius (about 60% of the virial radius) from the cluster center . The temperature drops radially to 0.5-0.6 of the peak value at a radius of \sim 15'. The gas-mass-weighted metal abundance averaged over the observed region is found to be 0.21 +- 0.05 times solar.
05/2008;
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[show abstract]
[hide abstract]
ABSTRACT: Two nearby clusters of galaxies: A194 (z=0.018) and A1060 (z=0.0114) have been analyzed for their X-ray point source properties with XMM-Newton EPIC-PN data. A multi-band source detection technique was applied to both of the clusters, resulting in 46 sources from the A194 field and 32 sources from the A1060 field, respectively. The cumulative log(N)-log(S) for a flux limit of Fx~10E-14 ergs cm-2 s-1 is calculated and compared with that of the Lockman Hole. A ~3 sigma excess of X-ray sources is found for the cluster regions. Considering the higher fraction observed in optical studies from the clusters, we estimate that the cluster source density is 6 times higher than the blank field source density, and 15 times higher than the local group. Our X-ray selected sources have luminosity values between 10E(39.6)<Lx<10E(41.4) ergs/s, in which X-ray emission from LMXBs, hot halos and starburst galaxies becomes noticeable. The significance of the source density excess vanishes gradually for sources with Lx > 10E(40.5) ergs/s, at which point the source density becomes comparable to that of the blank-field level. Considering this confined low luminosity range and the X-ray to optical luminosity ratios (L_X/L_B), the observed overdensity is ascribed to AGN fueling by its infall into cluster environment for Lx < 10E(40.5) ergs/s in the X-ray luminosity function. Whereas, the quenching of AGN activity by the deep cluster potential explains why the excess of the source density vanishes for the brighter sources.
04/2008;
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[show abstract]
[hide abstract]
ABSTRACT: We are planning to have a "formation flight all sky telescope" FFAST) that will cover a large sky area in relatively high energy X-ray. In particular, it will focus on the energy range above 10 keV. It consists of two small satellites that will go in a formation flight. One is an X-ray telescope satellite and the other is a detector satellite. Two satellites will be simultaneously launched by a single rocket vehicle into a low earth orbit. They are in a formation flight with a separation of 20 m±10 cm. The observation direction is determined by the two satellites. Since two satellites are put into Keplerian orbit, the observation direction is scanning the sky rather than pointing to a fixed direction. The X-ray telescope satellite carries one super-mirror covering the energy range up to 80 keV. The telescope is 45-cm diameter and its focal length is 20 m. The telescope is a "super mirror" hat has a multi-layer coating covering the energy range up to 80 keV. The effective area is about 500 cm 2 at low energy and 200 cm 2 at 70 keV. The mirror system is a thin foil mirror that is developing at Nagoya University that is being developed. The PSF of the mirror will be about 1-2 arcmin. The satellite is equipped with an attitude control system using momentum wheel. It will keep the satellite such that the optical axis of the mirror is pointing to the detector satellite. The other is a detector satellite that carries an SDCCD system. The SDCCD is a CCD with a scintillator that is directly attached to the CCD. The CCD chip is fully depleted which can be a back-illuminated CCD. The scintillator is attached to the CCD at back side so that it has high detection efficiency for visible photons generated inside the scintillator. The X-ray enters into the CCD at front side. Therefore, low energy X-rays (below 10 keV) can be photo-absorbed in the depletion layer of the CCD while high energy X-rays will be absorbed in the scintillator that will emit visible photons The visible photons can be detected by the CCD. Depletion layer events usually form small charge spread while scintillator events usually form large charge spread. These events generate charge spread in a symmetric form with different size. On the contrary, charged particles leave an elongated charge spread that can be distinguished from X-ray events by pattern recognition. This project, Formation Flight All Sky Telescope (FFAST), will scan a large sky area at hard X-ray region.
70112D. 01/2008; 7011.
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Hisamitsu Awaki,
Naohisa Anabuki,
Yasushi Fukazawa,
Luigi C. Gallo,
Shinya Ikeda,
Naoki Isobe,
Takeshi Itoh, Hideyo Kunieda,
Kazuo Makishima,
Alex Markowitz,
Giovanni Miniutti,
Tsunefumi Mizuno,
Takashi Okajima,
Andrew Ptak,
James N. Reeves,
Tadayuki Takahashi,
Yuichi Terashima,
Tahir Yaqoob
[show abstract]
[hide abstract]
ABSTRACT: We obtained a wide-band spectrum of the Compton-thick Seyfert2 galaxy
Mkn3 with Suzaku. The observed spectrum was clearly resolved into
weak, soft power-law emission, a heavily absorbed power-law component,
cold reflection, and many emission lines. The heavily absorbed
component, absorbed by gas with a column density of 1.1 ×
1024 cm-2, has an intrinsic 2-10keV luminosity of
˜1.6×1043 ergs-1, and is considered to
be direct emission from the Mkn3 nucleus. The reflection component was
interpreted as being the reflection of direct light off a cold, thick
material; the reflection fraction, R, was 1.36±0.20. The cold
material is inferred to be located > 1 pc from the central black
hole of Mkn3, due to the low ionization parameter of iron (xi <
1ergcms-1) and the narrow iron line width (σ <
22eV). The weak, soft power-law emission is considered to be scattered
light by ionized gas with a scattering fraction of 0.9±0.2%. The
existence of many highly ionized lines in the observed spectrum
indicates that the ionized gas has a broad ionized structure, with xi =
10--1000 erg cm s-1. This high-quality spectrum obtained by
Suzaku can be considered to be a template for studies of Seyfert2
galaxies.
Publications- Astronomical Society of Japan 12/2007; 60:293. · 2.44 Impact Factor
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Hisamitsu Awaki,
Naohisa Anabuki,
Yasuchi Fukazawa,
Luigi Gallo,
Shinya Ikeda,
Naoki Isobe,
Takeshi Itoh, Hideyo Kunieda,
Kazuo Makishima,
Alex G. Markowitz,
Giovanni Miniutti,
Tsunefumi Mizuno,
Takashi Okajima,
Andrew Ptak,
James N. Reeves,
Tadayuki Takahashi,
Yuichi Terashima,
Tahir Yaqoob
[show abstract]
[hide abstract]
ABSTRACT: We obtained a wide-band spectrum of the Compton-thick Seyfert 2 galaxy Mrk 3 with Suzaku. The observed spectrum was clearly resolved into weak, soft power-law emission, a heavily absorbed power-law component, cold reflection, and many emission lines. The heavily absorbed component, absorbed by gas with a column density of 1.1x10^24 cm^-2, has an intrinsic 2--10 keV luminosity of ~1.6x10^43 erg s^-1, and is considered to be direct emission from the Mrk 3 nucleus. The reflection component was interpreted as reflection of the direct light off cold, thick material; the reflection fraction $R$ was 1.36+/-0.20. The cold material is inferred to be located > 1 pc from the central black hole of Mrk 3 due to the low ionization parameter of iron (xi < 1 erg cm s^-1) and the narrow iron line width (s < 22 eV). A Compton shoulder to the iron line was detected, but the intensity of the shoulder component was less than that expected from spherically distributed Compton-thick material. The weak, soft power-law emission is considered to be scattered light by ionized gas. The existence of many highly-ionized lines from O, Ne, Mg, Si, S, and Fe in the observed spectrum indicates that the ionized gas has a broad ionized structure, with xi=10--1000. The scattering fraction with respect to the direct light was estimated to be 0.9+/-0.2%, which indicates that the column density of the scattering region is about 3.6x10^22 cm^-2. This high-quality spectrum obtained by Suzaku can be considered a template for studies of Seyfert 2 galaxies.
08/2007;
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[show abstract]
[hide abstract]
ABSTRACT: Two nearby clusters of galaxies, A194 (z=0.018) and A1060 (z=0.0114),
have been analyzed for their X-ray point-source properties with
XMM-Newton EPIC-PN data. A multi-band source detection technique was
applied to both of the clusters, resulting in 46 sources from the A194
field and 32 sources from the A1060 field, respectively. The cumulative
log(N)-log(S) for a flux limit of FX ≥ 1 ×
10-14erg cm-2 s-1 was calculated and
compared with that of the Lockman Hole. A ˜ 3σ excess of
X-ray sources was found for the cluster regions. Considering the higher
fraction observed in optical studies from the clusters, we estimate that
the cluster source density is 6-times higher than the blank-field source
density, and 15-times higher than the local group. Our X-ray selected
sources have luminosity values of 1039.6 ≤ LX
≤ 1041.4 erg s-1, in which X-ray emission from
LMXBs, hot halos and starburst galaxies becomes noticeable. The
significance of the source-density excess gradually vanishes for sources
with LX ≥ 1040.5erg s-1, at which
point the source density becomes comparable to that of the blank-field
level. Considering this confined low-luminosity range and the X-ray to
optical luminosity ratios (LX/LB), the observed
overdensity is ascribed to AGN fueling by its infall into cluster
environment for LX ≤ 1040.5 erg s-1
in the X-ray luminosity function. However, the quenching of AGN activity
by the deep cluster potential explains why the excess of the source
density vanishes for brighter sources.
Publications- Astronomical Society of Japan 11/2006; 58:931-943. · 2.44 Impact Factor
