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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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[show abstract]
[hide abstract]
ABSTRACT: We report on the performance of an analog application-specific integrated
circuit (ASIC) developed aiming for the front-end electronics of the X-ray
CCDcamera system onboard the next X-ray astronomical satellite, ASTRO-H. It has
four identical channels that simultaneously process the CCD signals.
Distinctive capability of analog-to-digital conversion enables us to construct
a CCD camera body that outputs only digital signals. As the result of the
front-end electronics test, it works properly with low input noise of =<30 uV
at the pixel rate below 100 kHz. The power consumption is sufficiently low of
about 150 mW/chip. The input signal range of 720 mV covers the effective energy
range of the typical X-ray photon counting CCD (up to 20 keV). The integrated
non-linearity is 0.2% that is similar as those of the conventional CCDs in
orbit. We also performed a radiation tolerance test against the total ionizing
dose (TID) effect and the single event effect. The irradiation test using 60Co
and proton beam showed that the ASIC has the sufficient tolerance against TID
up to 200 krad, which absolutely exceeds the expected amount of dose during the
period of operating in a low-inclination low-earth orbit. The irradiation of Fe
ions with the fluence of 5.2x10^8 Ion/cm2 resulted in no single event latchup
(SEL), although there were some possible single event upsets. The threshold
against SEL is higher than 1.68 MeV cm^2/mg, which is sufficiently high enough
that the SEL event should not be one of major causes of instrument downtime in
orbit.
02/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We observed the luminous narrow-line Seyfert 1 galaxy Ton S180 with
Suzaku, and obtained its wide-band (0.25-55 keV) X-ray spectra for the
first time. The spectra were modeled with three components: a power-law
component, a reflection from a highly ionized disk component, and an
extra soft component either of a disk blackbody or a cutoff power-law.
The reflection component accounts for the broad iron K line centered at
6.7 keV, and some fraction of the soft X-ray excess, including the O VIII
line emission. The latter two components contribute comparably to the soft
X-ray excess. When we adopt the disk blackbody model as the extra soft
component, the disk inner radius temperature is 75 eV, much smaller than
previously considered. This component is almost consistent with that expected
for the slim-disk model assuming edge-on geometry. Hard X-ray emission above
15 keV was marginally detected. To account for the hard X-ray spectrum, we
introduced Compton-thick partial absorbers. The absence of the neutral
iron K line requires that those absorbers must be preferentially located
along the line of sight. Fractional variability has little energy
dependence below 10 keV, and is explained with a model in which the
covering fraction of the Compton-thick absorber alters the observed
flux.
Publications- Astronomical Society of Japan 11/2010; 62:1483. · 2.44 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: We report the results from our analysis of Suzaku X-ray Imaging Spectrometer (XIS) (0.5-10 keV) and Hard X-ray Detector (HXD)/PIN (15-40 keV) observations of five well-known local ultraluminous infrared galaxies: IRAS F05189 – 2524, IRAS F08572 + 3915, Mrk 273, PKS 1345 + 12, and Arp 220. The XIS observations of F05189 – 2524 and Mrk 273 reveal strong iron lines consistent with Fe Kα and changes in spectral shapes with respect to previous Chandra and XMM-Newton observations. Mrk 273 is also detected by the HXD/PIN at ~ 1.8σ. For F05189 – 2524, modeling of the data from the different epochs suggests that the change in spectral shape is likely due to the central source switching off, leaving behind a residual reflection spectrum, or an increase in the absorbing column. An increase in the covering fraction of the absorber can describe the spectral variations seen in Mrk 273, although a reduction in the intrinsic active galactic nucleus (AGN) luminosity cannot be formally ruled out. The Suzaku spectra of Mrk 273 are well fitted by a ~ 94% covering fraction model with a column density of ~ 1024 cm–2. The absorption-corrected log[L 2-10keV/L IR] ratio is consistent with those found in PG Quasars. The 0.5-10 keV spectrum of PKS 1345 + 12 and Arp 220 seem unchanged from previous observations and their hard X-ray emission is not convincingly detected by the HXD/PIN. The large column density derived from CO observations and the large equivalent width of an ionized Fe line in Arp 220 can be reconciled by an ionized reflection model. F08572 + 3915 is undetected in both the XIS and HXD/PIN, but the analysis of unpublished Chandra data provides a new measurement at low energies.
The Astrophysical Journal 01/2009; 691(1):261. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We examine whether the ultraluminous infrared galaxies that contain a type 1 Seyfert nucleus (a type I ULIRG) are in the transition stage from ULIRGs to quasi-stellar objects (QSOs). To investigate this issue, we compare the black hole (BH) mass, the bulge luminosity, and the far-infrared luminosity among type I ULIRGs, QSOs, and elliptical galaxies. As a result, we find the following results: (1) The type I ULIRGs have systematically smaller BH masses in spite of the comparable bulge luminosity relative to QSOs and elliptical galaxies. (2) The far-infrared luminosity of most type I ULIRGs is larger than the Eddington luminosity. We show that the above results do not change significantly for three type I ULIRGs for which we can estimate the visual extinction from the column density. Also, for all eight type I ULIRGs, we investigate the effect of uncertainties of BH mass measurements and our sample bias to make sure that our results are not altered even if we consider the above two effects. In addition, Anabuki recently revealed that their X-ray properties are similar to those of the narrow-line Seyfert 1 galaxies. These would indicate that active galactic nuclei (AGNs) with a high mass accretion rate exist in type I ULIRGs. On the basis of all of these findings, we conclude that it would be a natural interpretation that type I ULIRGs are the early phase of BH growth, namely, the missing link between ULIRGs and QSOs. Moreover, by comparing our results with a theoretical model of a coevolution scenario of a QSO BH and a galactic bulge, we show clearly that this explanation could be valid.
The Astrophysical Journal 12/2008; 637(1):104. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We report the results from our analysis of {\it Suzaku} XIS (0.5-10 keV) and HXD/PIN (15-40 keV) observations of five well-known local ULIRGs: {\em IRAS} F05189-2524, {\em IRAS} F08572+3915, Mrk 273, PKS 1345+12, and Arp 220. The XIS observations of F05189-2524 and Mrk 273 reveal strong iron lines consistent with Fe K$\alpha$ and changes in spectral shapes with respect to previous {\it Chandra} and {\it XMM-Newton} observations. Mrk 273 is also detected by the HXD/PIN at $\sim$1.8-$\sigma$. For F05189-2524, modeling of the data from the different epochs suggests that the change in spectral shape is likely due to the central source switching off, leaving behind a residual reflection spectrum, or an increase in the absorbing column. An increase in the covering fraction of the absorber can describe the spectral variations seen in Mrk 273, although a reduction in the intrinsic AGN luminosity cannot be formally ruled out. The {\it Suzaku} spectra of Mrk 273 are well fit by a ~94% covering fraction model with a column density of $\sim10^{24}$ cm$^{-2}$. The absorption-corrected log[$L_{\rm 2-10 keV}$ / $L_{\rm IR}$] ratio is consistent with those found in PG Quasars. The 0.5-10 keV spectrum of PKS 1345+12 and Arp 220 seem unchanged from previous observations and their hard X-ray emission is not convincingly detected by the HXD/PIN. The large column density derived from CO observations and the large equivalent width of an ionized Fe line in Arp 220 can be reconciled by an ionized reflection model. F08572+3915 is undetected in both the XIS and HXD/PIN, but the analysis of unpublished {\em Chandra} data provides a new measurement at low energies. Comment: 37 pages including 4 tables and 10 figures. Accepted for publication in ApJ. It is tentatively scheduled to appear in the January 20, 2009 issue of ApJ
09/2008;
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[show abstract]
[hide abstract]
ABSTRACT: We present a comparison between the 2001 XMM–Newton and 2005 Suzaku observations of the quasar, PG 1211+143, at z= 0.0809. Variability is observed in the 7 keV iron K-shell absorption line (at 7.6 keV in the quasar frame), which is significantly weaker in 2005 than during the 2001 XMM–Newton observation. From a recombination time-scale of <4 yr, this implies an absorber density n > 4 × 103 cm−3, while the absorber column is 5 × 1022 < NH < 1 × 1024 cm−2. Thus, the size scale of the absorber is too compact (pc scale) and the surface brightness of the dense gas too high (by 9–10 orders of magnitude) to arise from local hot gas, such as the local bubble, group or warm/hot intergalactic medium (WHIM), as suggested by McKernan, Yaqoob & Reynolds. Instead, the iron K-shell absorption must be associated with an active galactic nucleus (AGN) outflow with mildly relativistic velocities. Finally, we show that the association of the absorption in PG 1211+143 with local hot gas is simply a coincidence, and the comparison between the recession and iron K absorber outflow velocities in other AGN does not reveal a one-to-one kinematic correlation.
Monthly Notices of the Royal Astronomical Society Letters 03/2008; 385(1):L108 - L112.
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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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[show abstract]
[hide abstract]
ABSTRACT: The metal abundances in the interstellar medium of the isolated
elliptical galaxy NGC 720 were studied with the CCD X-ray Imaging
Spectrometer (XIS) aboard the Suzaku satellite. The high detection
efficiency along with the excellent spectral resolution of the XIS
allowed the K-shell lines of O and Mg to be clearly resolved, and the
abundances of O, Ne, Mg, Si, and Fe to be measured with good accuracy
for the region within a 3' radius of NGC 720. The abundances of O and
Mg were well determined to be 0.4 and 0.5 solar respectively, meaning
stellar metallicity of mass-losing stars in NGC 720 was also well
determined. The abundance of Fe was determined to be about 0.7 solar,
while the O/Fe, Ne/Fe abundance ratios were found to be about 0.5 and
Mg/Fe, Si/Fe were found to be 0.7 in solar units. Relative errors of
30% for the O/Fe, Ne/Fe, Mg/Fe abundance ratios are the lowest among
isolated elliptical galaxies so far observed. The higher abundance of
Fe than those of O, Ne, and Mg supplied by stellar mass loss indicates
that iron is enhanced by SN Ia in NGC 720. These abundance ratios are
consistent with those in the ISM of NGC 1399, NGC 1404, and in the ICM
of the Fornax cluster observed with Suzaku.
Publications- Astronomical Society of Japan 12/2007; 60:307. · 2.44 Impact Factor
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Takeshi Itoh,
Chris Done,
Kazuo Makishima,
Grzegorz Madejski,
Hisamitsu Awaki,
Naoki Isobe,
Poshak Gandhi,
Gulab C. Dewangan,
Richard E. Griffiths, Naohisa Anabuki,
Takashi Okajima,
James Reeves,
Tadayuki Takahashi,
Yoshihiro Ueda,
Satohi Eguchi,
Tahir Yaqoob
[show abstract]
[hide abstract]
ABSTRACT: Suzaku observed a nearby Seyfert 2 galaxy NGC4945, which hosts one of the brightest active galactic nuclei above 20 keV. Combining data from the X-ray CCD camera (XIS) and the Hard X-ray Detector (HXD), the AGN intrinsic nuclear emission and its reprocessed signals were observed simultaneously. The intrinsic emission is highly obscured with an absorbing column of $\sim 5 \times 10^{24}$ cm$^{-2}$, and was detectable only above $\sim 10$ keV. The spectrum below 10 keV is dominated by reflection continuum and emission lines from neutral/ionized material. Along with a neutral iron K$\alpha$ line, a neutral iron K$\beta$ and a neutral nickel K$\alpha$ line were detected for the first time from this source. The neutral lines and the cold reflection continuum are consistent with both originating in the same location. The Compton down-scattered shoulder in the neutral Fe-K$\alpha$ line is $\sim 10%$ in flux of the narrow core, which confirms that the line originates from reflection rather than transmission. The weakness of the Compton shoulder also indicates that the reflector is probably seen nearly edge-on. Flux of the intrinsic emission varied by a factor of $\sim 2$ within $\sim 20$ ks, which requires the obscuring material to be geometrically thin. Broadband spectral modeling showed that the solid angle of the neutral reflector is less than a few $\times 10^{-2} \times 2\pi$. All this evidence regarding the reprocessed signals suggests that a disk-like absorber/reflector is viewed from a near edge-on angle.
09/2007;
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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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Giovanni Miniutti,
Andrew C. Fabian, Naohisa Anabuki,
Jamie Crummy,
Yasushi Fukazawa,
Luigi Gallo,
Yoshito Haba,
Kiyoshi Hayashida,
Steve Holt,
Hideyo Kunieda, [......],
James N. Reeves,
Tadayuki Takahashi,
Yasuo Tanaka,
Yuichi Terashima,
Ken'ichi Torii,
Yoshihiro Ueda,
Masayoshi Ushio,
Shin Watanabe,
Makoto Yamauchi,
Tahir Yaqoob
[show abstract]
[hide abstract]
ABSTRACT: Suzaku has, for the first time, enabled the hard X-ray variability of the Seyfert 1 galaxy MCG-6-30-15 to be measured. The variability in the 14-45 keV band, which is dominated by a strong reflection hump, is quenched relative to that at a few keV. This directly demonstrates that the whole reflection spectrum is much less variable than the power-law continuum. The broadband spectral variability can be decomposed into two components - a highly variable power-law and constant reflection - as previously inferred from other observations in the 2-10 keV band. The strong reflection and high iron abundance give rise to a strong broad iron line, which requires the inner disc radius to be at about 2 gravitational radii. Our results are consistent with the predictions of the light bending model which invokes the very strong gravitational effects expected very close to a rapidly spinning black hole.
10/2006;
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[show abstract]
[hide abstract]
ABSTRACT: We examine whether the ultraluminous infrared galaxies that contain a type I Seyfert nucleus (a type I ULIRG) are in the transition stage from ULIRGs to quasi-stellar objects (QSOs). To inspect this issue, we compare the black hole (BH) mass, the bulge luminosity and the far infrared luminosity among type I ULIRGs, QSOs and elliptical galaxies. As a result, we find the following results; (1) The type I ULIRGs have systematically smaller BH masses in spite of the comparable bulge luminosity relative to QSOs and elliptical galaxies. (2) The far-infrared luminosity of most type I ULIRGs is larger than the Eddington luminosity. We show that above results do not change significantly for 3 type I ULIRGs that we can estimate the visual extinction from the column density. Also, for all 8 type I ULIRGs, we investigate the effect of uncertainties of BH mass measurments and our sample bias, so that it turns out that our results do not alter even if we consider above two effects. In addition, Anabuki (2004) revealed that their X-ray properties are similar to those of the narrow line Seyfert 1 galaxies. These would indicate that active galactic nuclei (AGNs) with a high mass accretion rate exist in the type I ULIRGs. Based on all of these findings, we conclude that it would be a natural interpretation that type I ULIRGs are the early phase of BH growth, namely the missing link between ULIRGs and QSOs. Moreover, by comparing our results with a theoretical model of a coevolution scenario of a QSO BH and a galactic bulge, we show clearly that this explanation would be valid. Comment: 11 pages, 4 figures, 4 tables accepted for publication in ApJ
09/2005;
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[show abstract]
[hide abstract]
ABSTRACT: We present X-ray observations of the ultraluminous infrared galaxy, UGC 5101, thought to contain a buried active galactic nucleus (AGN) based on observations in other wavebands. We detected an absorbed hard component at >3 keV, as well as soft emission in the energy range 0.5-2 keV. The soft X-ray component, possibly due to a modestly dust-obscured, extended starburst, has an absorption-corrected 0.5-2 keV X-ray luminosity of LX(0.5-2 keV) = 1.2 * 10^41 ergs s^-1. The 0.5-2 keV X-ray to infrared luminosity ratio is a factor of 5 lower than typical values for a normal starburst, suggesting that this extended starburst is unlikely to be energetically dominant in UGC 5101. The most plausible origin of the absorbed hard component is the putative buried AGN. The 6.4 keV Fe K alpha emission line has a modest equivalent width (400 eV), suggesting that this hard component is direct emission from the AGN, rather than a scattered component. The absorption-corrected 2-10 keV X-ray luminosity of the buried AGN was estimated to be LX(2-10 keV) = 5 * 10^42 ergs s^-1. The intrinsic 2-10 keV X-ray luminosity and the 2-10 keV X-ray to infrared luminosity ratio are both comparable to values measured for Mrk 463, a Seyfert-2 galaxy of similar infrared luminosity. Comment: 12 pages, 2 figures, Accepted for Publication in ApJL
09/2003;
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[show abstract]
[hide abstract]
ABSTRACT: The electron scattering region (ESR) is one of important ingredients in Seyfert nuclei because it makes possible to observe the hidden broad line region (hereafter HBLR) in some type 2 Seyfert nuclei (hereafter S2s). However, little is known about its physical and geometrical properties. Using the number ratio of S2s with and without HBLR, we investigate statistically where the ESR is in Seyfert nuclei. Our analysis suggests that the ESR is located at radius between $\sim$ 0.01 pc and $\sim$ 0.1 pc from the central engine. We also discuss a possible origin of the ESR briefly. Comment: 5 pages and 1 figure. The Astrophysical Journal (Letters), in press
06/1999;
