研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 宇宙物理学研究系 助教
- 学位
- 博士(理学)(2002年3月 東京大学理学系研究科物理学専攻)
- J-GLOBAL ID
- 202001017082346100
- researchmap会員ID
- R000012159
経歴
10-
2019年4月 - 現在
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2018年4月 - 2019年3月
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2017年4月 - 2018年3月
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2016年4月 - 2017年3月
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2011年4月 - 2016年3月
学歴
2-
1999年4月 - 2002年3月
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1997年4月 - 1999年3月
受賞
2主要な論文
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The Astrophysical Journal 2023年8月1日 査読有り筆頭著者
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Monthly Notices of the Royal Astronomical Society 512(4) 5995-6006 2022年3月25日 査読有りABSTRACT The far-infrared counterpart of hotspot D, the terminal hotspot of the eastern jet hosted by the radio galaxy Cygnus A, is detected with Herschel Aperture photometry of the source performed in 5 photometric bands covering the wavelength range of 70–350 $\mu$m. After removing the contamination from another nearby hotspot, E, the far-infrared intensity of hotspot D is derived as 83 ± 13 and 269 ± 66 mJy at 160 and 350 $\mu$m, respectively. Since the far-infrared spectrum of the object smoothly connects to the radio one, the far-infrared emission is attributed to the synchrotron radiation from the radio-emitting electron population. The radio-to-near-infrared spectrum is confirmed to exhibit a far-infrared break feature at the frequency of $\nu _\mathrm{br}=2.0^{+1.2}_{-0.8} \times 10^{12}$ Hz. The change in energy index at the break (Δα = 0.5) is interpreted as the impact of radiative cooling on an electron distribution sustained by continuous injection from diffusive shock acceleration. By ascribing the derived break to this cooling break, the magnetic field, B, in the hotspot is determined as a function of its radius, R within a uniform one-zone model combined with the strong relativistic shock condition. An independent B–R constraint is obtained by assuming the X-ray spectrum is wholly due to synchrotron self-Compton emission. By combining these conditions, the two parameters are tightly determined as B = 120–150 μG and R = 1.3–1.6 kpc. A further investigation into the two conditions indicates the observed X-ray flux is highly dominated by the synchrotron self-Compton emission.
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The Astrophysical Journal 899(1) 17-17 2020年8月7日 査読有り筆頭著者
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The Astrophysical Journal 850(2) 193-193 2017年12月1日 査読有り筆頭著者Mid-infrared properties are reported of the west hot spot of the radio galaxy Pictor A with the Wide-field Infrared Survey Explorer (WISE). The mid-infrared counterpart to the hot spot, WISE J051926.26-454554.1, is listed in the AllWISE source catalog. The source was detected in all four of the WISE photometric bands. A comparison between the WISE and radio images reinforces the physical association of the WISE source to the hot spot. The WISE flux density of the source was carefully evaluated. A close investigation of the multi-wavelength synchrotron spectral energy distribution from the object reveals a mid-infrared excess at the wavelength of lambda = 22 mu m with a statistical significance of 4.8 sigma over the simple power-law extrapolation from the synchrotron radio spectrum. The excess is reinforced by single and double cutoff power-law modeling of the radio-to-optical spectral energy distribution. The synchrotron cutoff frequency of the main and excess components was evaluated as 7.1 x 10(14) Hz and 5.5 x 10(13) Hz, respectively. From the cutoff frequency, the magnetic field of the emission region was constrained as a function of the region size. In order to interpret the excess component, an electron population different from the main one dominating the observed radio spectrum is necessary. The excess emission is proposed to originate in a substructure within the hot spot, in which the magnetic field is a factor of a few stronger than that in the minimum-energy condition. The relation of the mid-infrared excess to the X-ray emission is briefly discussed.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68(6) 2016年12月Nearby active galactic nuclei were diagnosed in the X-ray and mid-to-far infrared wavelengths with Monitor of All-sky X-ray Image (MAXI) and the Japanese infrared observatory AKARI, respectively. One hundred of the X-ray sources listed in the second release of theMAXI all-sky X-ray source catalog are currently identified as non-blazar-type active galactic nuclei. These include 95 Seyfert galaxies and 5 quasars, and they are composed of 73 type-1 and 27 type-2 objects. The AKARI all-sky survey point source catalog was searched for their mid-and far-infrared counterparts at 9, 18, and 90 mu m. As a result, 69 Seyfert galaxies in the MAXI catalog (48 type-1 and 21 type-2) were found to be detected with AKARI. The X-ray (3-4 keV and 4-10 keV) and infrared luminosities of these objects were investigated, together with their color information. Adopting the canonical photon index, Gamma = 1.9, of the intrinsic X-ray spectrum of the Seyfert galaxies, the X-ray hardness ratio between the 3-4 and 4-10 keV ranges derived with MAXI was roughly converted into the absorption column density. After the X-ray luminosity was corrected for absorption from the estimated column density, the well-known X-ray-to-infrared luminosity correlation was confirmed, at least in the Compton-thin regime. In contrast, NGC 1365, the only Compton-thick object in the MAXI catalog, was found to deviate from the correlation toward a significantly lower X-ray luminosity by nearly an order of magnitude. It was verified that the relation between the X-ray hardness below 10 keV and X-ray-to-infrared color acts as an effective tool to pick up Compton-thick objects. The difference in the infrared colors between the type-1 and type-2 Seyfert galaxies and its physical implication on the classification and unification of active galactic nuclei are briefly discussed.
MISC
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VizieR On-line Data Catalog 2023年10月
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eprint arXiv:2307.05666 2023年7月
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Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave 2020年12月13日
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Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave 2018年7月12日
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Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray 10699 2018年7月6日© 2018 SPIE. Toward a new era of X-ray astronomy, next generation X-ray optics are indispensable. To meet a demand for telescopes lighter than the foil optics but with a better angular resolution less than 1 arcmin, we are developing micropore X-ray optics based on micromaching technologies. Using sidewalls of micropores through a thin silicon wafer, this type can be the lightest X-ray telescope ever achieved. Two new Japanese missions ORBIS and GEOX will carry this optics. ORBIS is a small X-ray astronomy mission to monitor supermassive blackholes, while GEO-X is a small exploration mission of the Earth's magnetosphere. Both missions need a ultra light-weight (<1 kg) telescope with moderately good angular resolution (<10 arcmin) at an extremely short focal length (<30 cm). We plan to demonstrate this optics in these two missions around 2020, aiming at future other astronomy and exploration missions.
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Space Telescopes and Instrumentation 2018: Ultraviolet to Gamma Ray 2018年7月6日
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宇宙航空研究開発機構特別資料 = JAXA Special Publication: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (17) 217-220 2018年3月9日第4回「あかり」国際会議 (2017年10月17-20日. 東京大学), 文京区, 東京形態: カラー図版あり資料番号: AA1730026036レポート番号: JAXA-SP-17-009E The 4th AKARI International Conference: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (October 17-20, 2017. The University of Tokyo), Bunkyo-ku, Tokyo, JapanWe analyzed the 4.67 micrometers CO ro-vibrational absorption band in nearby ten active galactic nuclei (AGNs) observed with AKARI and Spitzer by fitting a plane-parallel local thermal equilibrium gas model. We found that the CO gas is warm (200-500 K) with a large column density (N(sub H) less than in the order of 10(exp 23) cm-2). Such a large column of warm gas is not achievable with UV heating or shock heating in starbursts. The most convincing heating source is X-ray photons emitted from the nuclei, which can produce warm gas of N(sub H) in the order of 10(exp 24) cm-2. This indicates that the region probed by the CO absorption is in the vicinity of the nuclei. The hydrogen column density estimated from the CO band is smaller than that inferred from X-ray observations. The observed deep absorption implies that the gas is close to the continuum source. We suggest that the probed region is outside the X-ray emitting region and just in front of the dust sublimation layer, which can be designated as the inner rim of the obscuring material around the AGNs.Physical characteristics: Original contains color illustrations
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宇宙航空研究開発機構特別資料 = JAXA Special Publication: Proceedings of the SPICA Science Conference from Exoplanets to Distant Galaxies: SPICA's New Window on the Cool Universe (17) 117-119 2018年3月9日形態: カラー図版あり資料番号: AA1730027026レポート番号: JAXA-SP-17-010E SPICA Science Conference from Exoplanets to Distant Galaxies: SPICA's New Window on the Cool Universe (June 18-21, 2013. Ito Hall, the University of Tokyo), Bunkyou-ku, Tokyo, JapanWe carried out systematic observations of the HI recombination line Bra (4.05 μm) in nearby (z less than 0.3) ultraluminous infrared galaxies (ULIRGs), using AKARI near-infrared 2.5-5.0 μm spectroscopy. We derived star formation rates (SFRs) from the Bra line, whose observed flux is predicted to be the highest among HI recombination lines in conditions with large dust extinction (visual extinction Av greater than 15 mag) expected in ULIRGs. Using the 3.3 μm polycyclic aromatic hydrocarbon emission in addition to the Bra line as an indicator of the SFR, we estimated the contribution of the star formation to the total infrared luminosity in 51 ULIRGs. The contribution was on average 28 plus or minus4 0/o in ULIRGs optically classified as H II, while 14 plus or minus2 0/o in ULIRGs optically classified as LINER or Seyfert. This result indicates that the star formation is significantly active in H II ULIRGs and other energy source, i.e. active galactic nuclei, is needed in LINER ULIRGs.Physical characteristics: Original contains color illustrations
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宇宙航空研究開発機構特別資料 = JAXA Special Publication: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (17) 379-382 2018年3月9日第4回「あかり」国際会議 (2017年10月17-20日. 東京大学), 文京区, 東京形態: カラー図版あり資料番号: AA1730026077レポート番号: JAXA-SP-17-009E The 4th AKARI International Conference: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (October 17-20, 2017. The University of Tokyo), Bunkyo-ku, Tokyo, JapanWe made systematic observations of the HI Br alpha (4.05 micrometers) and Br beta (2.63 micrometers) lines in 52 nearby (z less than 0.3) ULIRGs with AKARI. Our observations show that ULIRGs have a tendency to indicate higher Br beta/Br alpha line ratios than those observed in Galactic HII regions, and three galaxies in the observed sample show the anomaly of the Br beta/Br alpha line ratios (in the order of 1.0), which are significantly higher than that of case B (0.565). The high Br beta/Br alpha line ratios cannot be explained by the combination of the dust extinction and the case B, since dust extinction reduces the ratio. We simulate HII regions in the ULIRGs with the Cloudy code, and show that the high Br beta/Br alpha line ratios can be explained with the combination of the optically thick Br alpha line and the optically thin Br beta line. To achieve the column density large enough to make the Br alpha line optically thick, the gas density is required as high as n in the order of 10(exp 8) cm(exp -3). Hence our results suggest that star-formation activity in ULIRGs occurs preferentially in high-density clouds.Physical characteristics: Original contains color illustrations
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宇宙航空研究開発機構特別資料 = JAXA Special Publication: The Cosmic Wheel and the Legacy of the AKARI archive: from galaxies and stars to planets and life (17) 325-327 2018年3月9日第4回「あかり」国際会議 (2017年10月17-20日. 東京大学), 文京区, 東京形態: カラー図版あり資料番号: AA1730026063レポート番号: JAXA-SP-17-009E
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Astrophysical Journal 753(2) 2012年7月10日We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10keV) properties for local active galactic nuclei (AGNs). The Swift Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray-detected AGNs. Cross-correlating the 22month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGNs detected by the AKARI instruments. We find a strong correlation for most AGNs between the infrared (9, 18, and 90 μm) and hard X-ray (14-195keV) luminosities, and quantify the correlation for various subsamples of AGNs. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1 galaxies, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick (CT) sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity versus infrared color diagram, in which type 1 radio-loud AGNs are well isolated from the others in the sample. The other uses the X-ray versus infrared color as a useful redshift-independent indicator for identifying CT AGNs. Importantly, CT AGNs and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR. © 2012. The American Astronomical Society. All rights reserved..
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 63(2) 397-405 2011年4月The Solid-state Slit Camera (SSC) is an X-ray camera aboard the MAXI mission of the International Space Station. Two sets of SSC sensors view the X-ray sky using charge-coupled devices (CCDs) in the 0.5-12 keV band. The total area for X-ray detection is about 200 cm(2), which is the largest among the missions of X-ray astronomy. The energy resolution at the CCD temperature of -70 degrees C is 145 eV in full width at the half maximum (FWHM) at 5.9 keV, and the field of view is 1.degrees 5 (FWHM) x 90 degrees for each sensor. The SSC could make a whole-sky image With the energy resolution good enough to resolve line emissions, and monitor the whole-sky at the energy band of <2 keV for the first time in these decades.
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SPACE TELESCOPES AND INSTRUMENTATION 2010: ULTRAVIOLET TO GAMMA RAY 7732 77320Z-77320Z-18 2010年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 similar to 7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued.
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ASTROPHYSICAL JOURNAL 706(1) 454-463 2009年11月A Suzaku observation of a giant radio galaxy, 3C 326, which has a physical size of about 2 Mpc, was conducted on 2008 January 19-21. In addition to several X-ray sources, diffuse emission was significantly detected and associated with its west lobe, but the east lobe was contaminated by an unidentified X-ray source WARP J1552.4+2007. After careful evaluation of the X-ray and non-X-ray background, the 0.4-7 keV X-ray spectrum of the west lobe is described by a power-law model modified with the Galactic absorption. The photon index and 1 keV flux density were derived as Gamma = 1.82(-0.24)(+0.26) +/- 0.04 and S-X = 19.4(-3.2)(+3.3) +/- 3.0 nJy, respectively, where the first and second errors represent the statistical and systematic ones. The diffuse X-rays were attributed to be inverse Compton (IC) radiation by the synchrotron radio electrons scattering off the cosmic microwave background photons. This radio galaxy is the largest among those with lobes detected through IC X-ray emission. A comparison of the radio to X-ray fluxes yields the energy densities of electron and magnetic field as u(e) = (2.3 +/- 0.3 +/- 0.3) x 10(-13) erg cm(-3) and u(m) = (1.2(-0.1)(+0.2) +/- 0.2) x 10(-14) erg cm(-3), respectively. The galaxy is suggested to host a low-luminosity nucleus with an absorption-corrected 2-10 keV luminosity of < 2 x 10(42) erg s(-1), together with a relatively weak radio core. The energetics in the west lobe of 3C 326 were compared with those of moderate radio galaxies with a size of similar to 100 kpc. The west lobe of 3C 326 is confirmed to agree with the correlations for the moderate radio galaxies, u(e) proportional to D-2.2 +/- 0.4 and u(m) proportional to D-2.4 +/- 0.4, where D is their total physical size. This implies that the lobes of 3C 326 are still being energized by the jet, despite the current weakness of the nuclear activity.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 61 S327-S335 2009年1月An observation of the West lobe of radio galaxy Fornax A (NGC 1316) with Suzaku is reported. Since Feigelson et al. (1995, ApJ, 449, L149) and Kaneda et al.(1995, AN, 453, L13) discovered the cosmic microwave background boosted inverse-Comptonized (IC) X-rays from the radio lobe, the magnetic field and electron energy density in the lobes have been estimated under the assumption that a single component of the relativistic electrons generates both the IC X-rays and the synchrotron radio emission. However, electrons generating the observed IC X-rays in the 1-10 keV band do not possess sufficient energy to radiate the observed synchrotron radio emission under the estimated magnetic field of a few mu G. On the basis of observations made with Suzaku, we show in the present paper that a 0.7-20 keV spectrum is well described by a single power-law model with an energy index of 0.68 and a flux density of 0.12 +/- 0.01 nJy at 1 keV from the West lobe. The derived multiwavelength spectrum strongly suggests that a single electron energy distribution over a Lorentz factor gamma = 300-90000 is responsible for generating both the X-ray and radio emissions. The derived physical quantities are not only consistent with those reported for the West lobe, but are also in very good agreement with those reported for the East lobe.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 61 S377-S386 2009年1月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).
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 60 S317-S331 2008年2月The compact group of galaxies HCG 62 (z = 0.0145) was observed for 120 ks with Suzaku XIS and HXD-PIN. The XIS spectra for four annular regions were fitted with a two-temperature vapec model with variable abundance, combined with the foreground Galactic component. The Galactic component was described by a two-temperature apec model, and constrained to have a common surface brightness among the four annuli. We confirmed the multitemperature nature of the intra-group medium, as reported previously, with a doughnut-like high temperature ring at radii 3'3-6'5. Abundances of Mg, Si, S, and Fe were well-constrained. We examined the possible "high-abundance arc" at'- 2; southwest from the center; however, Suzaku data did not confirm it. We suspect that it is a misidentification of an excess hot component in this region as the Fe line. Neither XIS (5-12 keV) nor HXD-PIN (12-40 keV) gave positive detection of the extended hard X-rays previously reported with ASCA, although our upper limit did not exclude the ASCA result. The 5-12 keV intensity in the r < 33 region turned out to be 70 19% higher than the nominal CXB level, and Chandra and Suzaku data suggest a concentration of hard X-ray sources with an average photon index of F = 1.3 8 0.06. The cumulative mass of 0, Fe, and Mg in the intra-group medium and the metal mass-to-light ratio were compared with those in other groups. The possible role of AGN or galaxy mergers in this group is also discussed.
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PASJ : publications of the Astronomical Society of Japan 59(1) S257-S267 2007年1月31日Two ultraluminous X-ray sources (ULXs) in the nearby Sb galaxy NGC 1313, named X-1 and X-2, were observed with Suzaku on 2005 September 15. During the observation for a net exposure of 28 ks (but over a gross time span of 90 ks), both objects varied in intensity by about 50%. The 0.4–10 keV X-ray luminosities of X-1 and X-2 were measured as 2.5×1040 ergs-1 and 5.8×1039 ergs-1, respectively, with the former exhibiting the highest ever reported for this ULX. The spectrum of X-1 can be explained by the sum of a strong and variable powerlaw component with a high-energy cutoff, and a stable multicolor blackbody with an innermost disk temperature of ∼ 0.2keV. These results suggest that X-1 was in a "very high" state, where disk emission is strongly Comptonized. The absorber within NGC 1313 toward X-1 is suggested to have a subsolar oxygen abundance. The spectrum of X-2 is best represented, in its fainter phase, by a multicolor blackbody model with an innermost disk temperature of 1.2–1.3 keV, and becomes flatter as the source becomes brighter. Hence, X-2 is interpreted to be in a slim-disk state. These results suggest that the two ULXs have black hole masses of some dozens to a few hundred of solar masses.
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PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT 169(169) 312-315 2007年It may seem to be difficult to analyze the Suzaku data, but the data structure and the tools are rather simple. We have constructed the way to process Suzaku FITS data and ftools for over ten years. We have prepared three kinds of manuals to analyze the data; Seven step manual of the XIS and the HXD for beginners, first step manual to walk through the analyses, and the ABC guide as a full manual. In the actual analyses, we have to be careful about events in operation and the limitations in the calibration of instruments. In this paper, the data structure, tools, and manuals with activities of help desks, current status of processing are summarized.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 59 S53-S76 2007年1月The in-orbit performance and calibration of the Hard X-ray Detector (HXD) on board the X-ray astronomy satellite Suzaku are described. Its basic performances, including a wide energy bandpass of 10-600keV, energy resolutions of similar to 4 keV (FWHM) at 40 keV and similar to 11% at 511 keV, and a high background rejection efficiency, have been confirmed by extensive in-orbit calibrations. The long-term gains of PIN-Si diodes have been stable within 1% for half a year, and those of scintillators have decreased by 5-20%. The residual non-X-ray background of the HXD is the lowest among past non-imaging hard X-ray instruments in energy ranges of 15-70 and 150-500 keV. We provide accurate calibrations of energy responses, angular responses, timing accuracy of the HXD, and relative normalizations to the X-ray CCD cameras using multiple observations of the Crab Nebula.
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ASTROPHYSICAL JOURNAL 645(1) 256-263 2006年7月An XMM-Newton observation of the east radio lobe of the nearby radio galaxy Fornax A is reported. The diffuse hard X-ray emission associated with the east lobe, which was initially discovered by ASCA and ROSAT, is confirmed with significant signal statistics, after strictly removing 59 sources detected within the MOS field of view. Its X-ray spectrum is described by a single power-law model, which is absorbed by a medium with a column density consistent with that toward the object. The best-fit X-ray photon index, Gamma(X) = 1.62(-0.15)(+0.24), agrees with the synchrotron radio index, Gamma(R) = 1.68 +/- 0.1, determined from the radio spectrum between 29.9 MHz and 5 GHz. Hence, the inverse Compton interpretation for the diffuse X-rays is justified. The X-ray flux density in the east lobe is measured to be 90 +/- 21 nJy at 1 keV (including both statistical and systematic errors) with the index fixed at the radio value. This gives electron and magnetic energy densities of 3.0(-1.0)(+1.5) x 10(-13) and 6.1(-3.5)(+5.7) x 10(-14) ergs cm(-3), respectively. The latter corresponds to a magnetic field strength of 1.24(-0.40)(+0.50) mu G, which is smaller than the field estimated under the minimum energy condition, 1.55 mu G, although with a slightly large error. Reevaluation is also made of the ASCA result on the west lobe, to show that both lobes share a similar physical condition in terms of energetics.
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PROCEEDINGS OF THE X-RAY UNIVERSE 2005, VOLS 1 AND 2 604 569-+ 2006年NGC 1316 hosts the classical double lobe radio galaxy Fornax A. Recently, Kim and Fabbiano (2003) revealed with Chandra a 'blob' like emission associated with the optical dark lane, suggesting heating by the galaxy-merging. In this paper, we show a detail analysis focusing into the 'blob' to show significantly low temperature and low entropy. The significantly lower entropy in comparison with the other inter-stellar medium structures supports that the 'blob' are produced at the past galaxy merging. Comparing with those of non-thermal electrons in the radio lobes, we discuss a possible history of the nucleus activity and show its estimated kinetic luminosity during its active phase.
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Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray, Pts 1 and 2 6266(No.) U2663-U2663 2006年Monitor of All-sky X-ray Image (MAXI) is an X-ray all-sky scanner, which will be attached on Exposed Facility of Japanese Experiment Module dubbed "Kibo" of International Space Station (ISS). MAXI will be launched by the Space Shuttle or the Japanese H-IIA Transfer Vehicle (HTV) in 2008. MAXI carries two types of X-ray cameras: Solid-state Slit Camera (SSC) for 0.5 - 10 keV and Gas Slit Camera (GSC) for 2 - 30 keV bands. Both have long narrow fields of view (FOV) made by a slit and orthogonally arranged collimator plates (slats). The FOV will sweep almost the whole sky once every 96 minutes by utilizing the orbital motion of ISS. Then the light curve of an X-ray point source become triangular shape in one transit. In this paper, we present the actual triangular response of the GSC collimator, obtained by our calibration. In fact they are deformed by gaps between the slats, leaning angle of the slats, and the effective width of the slats. We are measuring these sizes by shooting X-ray beams into the detector behind the collimator. We summarize the calibration and present the first compilation of the data to make the GSC collimator response, which will be useful for public users.
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ASTROPHYSICAL JOURNAL 632(2) 781-787 2005年10月The XMM-Newton observation of the nearby FR II radio galaxy 3C 98 is reported. In two exposures on the target, faint diffuse X-ray emission associated with the radio lobes was significantly detected together with a bright X-ray active nucleus, of which the 2-10 keV intrinsic luminosity is (4-8) x 10(42) ergs s(-1). The EPIC spectra of the northern and southern lobes are reproduced by a single power-law model modified by the Galactic absorption, with a photon index of 2.2(-0.5)(+0.6) and 1.7(-0.6)(+0.7), respectively. These indices are consistent with that of the radio synchrotron spectrum, 1.73 +/- 0.01. The luminosities of the northern and southern lobes are measured to be 8.3(-2.6)(+3.3) x 10(40) and 9.2+(5.7)(-4.3) x 10(40) ergs s(-1), respectively, in the 0.7-7 keV range. The diffuse X-ray emission is interpreted as an inverse Compton emission, produced when the synchrotron-emitting energetic electrons in the lobes scatter off the cosmic microwave background photons. The magnetic field in the lobes is calculated to be about 1.7 mu G, which is about 2.5 times lower than the value estimated under the minimum energy condition. It is inferred that the energy density of the electrons exceeds that in the magnetic fields by a factor of 40-50.
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UV AND GAMMA-RAY SPACE TELESCOPE SYSTEMS, PTS 1 AND 2 5488(No.) 197-208 2004年Monitor of All-sky X-ray Image (MAXI) is an X-ray all-sky monitor, which will be delivered to the International Space Station (ISS) in 008, to scan almost the whole sky once every 96 minutes for a mission life of two years. The detection sensitivity will be 7 mCrab (5sigma level) in one scan, and 1 mCrab for one-week accumulation. At previous SPIE meetings, we presented the development status of the MAXI payload, in particular its X-ray detectors. In this paper, we present the whole picture of the MAXI system, including the downlink path and the MAXI ground system. We also examine the MAXI system components other than X-ray detectors from the point of view of the overall performance of the mission. The engineering model test of the MAXI X-ray slit collimator shows that we can achieve the position determination accuracy of <0.1 degrees, required for the ease of follow-up observations. Assessing the downlink paths, we currently estimates that the MAXI ground system receive more than 50% of the observational data in "real time" (with time delay of a few to ten seconds), and the rest of data with delay of 20 minutes to a few hours from detection, depending on the timing of downlink. The data will be processed in easily-utilised formats, and made open to public users through the Internet.
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X-RAY AND GAMMA-RAY INSTRUMENTATION FOR ASTRONOMY XIII 5165(No.) 354-365 2004年The current status is reported of the development of Monitor of All-sky X-ray Image and the measurement of its observational response. MAXI is a scanning X-ray camera to be attached to the Japanese Experiment Module of the International Space Station in 2008. MAXI is mainly composed of two kinds of instruments, GSC which is sensitive to the 2 - 30 keV photons, and SSC to the 0.5 - 10 keV ones. As an X-ray all-sky monitor, MAXI has an unprecedented sensitivity of 7 mCrab in one orbit scan, and I mCrab in one week. Using the engineering mode of the proportional counter and of the collimator for GSC, the observational response of GSC is extensively measured. The acceptable performances are obtained as a whole for both the collimator and the counter. The engineering models of the other part of MAXI are also constructed and the measurement of their performance is ongoing.
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ASTROPHYSICAL JOURNAL 580(2) L111-L115 2002年12月An 80 ks Chandra ACIS observation of the radio galaxy 3C 452 is reported. A diffuse X-ray emission associated with the lobes has been detected with high statistical significance, together with the X-ray nucleus of the host galaxy. The 0.5-5 keV ACIS spectrum of the diffuse emission is described by a two-component model, consisting of a soft thermal plasma emission from the host galaxy halo and a hard nonthermal power-law component. The hard component is ascribed to the inverse Comptonization of cosmic microwave background photons by the synchrotron-emitting electrons in the lobes, because its spectral energy index, 0.68 +/- 0.28, is consistent with the radio synchrotron index, 0.78. These results reveal a significant electron dominance in the lobes. The electrons are inferred to have a relatively uniform distribution, while the magnetic field is compressed toward the lobe periphery.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 53(1) 79-83 2001年2月The X-ray properties of the BL Lacertae object OJ 287, observed with ASCA on 1997 April 26 and November 17, are reported. The 0.5-10 keV flux was lower than that obtained in previous X-ray observations, and no evidence of intensity variations was found during each observation. The obtained flux densities at 1 keV, 0.22-0.26 mu Jy, exceed the extrapolations from lower frequency synchrotron continua, which were measured in nearly the same period as the present ASCA observations. The X-ray spectra acquired with the GIS and SIS were consistently described with a single power-law model modified by the Galactic absorption, and the derived photon indices, 1.5-1.6, are flatter than those observed so far. These results strongly suggest that the X-ray spectra observed in 1997 arise via an inverse Compton process alone. The X-ray spectra obtained in 1994 (Idesawa et al. 1997, AAA 68.159.334), exhibiting a steeper slope than those in 1997, is thought to be contaminated by a "synchrotron soft tail".
講演・口頭発表等
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The 32nd Texas Symposium on Relativistic Astrophysics 2023年12月15日
共同研究・競争的資金等の研究課題
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日本学術振興会 科学研究費助成事業 2023年4月 - 2026年3月
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日本学術振興会 科学研究費助成事業 2021年4月 - 2025年3月
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日本学術振興会 科学研究費助成事業 2010年 - 2012年
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日本学術振興会 科学研究費助成事業 2008年 - 2011年
