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 招聘研究開発員
- 学位
- 理学博士(中央大学)理学修士(中央大学)
- J-GLOBAL ID
- 201201017168289883
- researchmap会員ID
- 7000000018
学歴
4-
- 2011年
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- 2008年
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- 2006年
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- 2002年
委員歴
1-
2012年
論文
27-
Monthly Notices of the Royal Astronomical Society 484(2) 2229-2233 2019年4月 査読有り
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70(6) 2018年10月1日We present the results from the Hitomi Soft Gamma-ray Detector (SGD)<br /> observation of the Crab nebula. The main part of SGD is a Compton camera, which<br /> in addition to being a spectrometer, is capable of measuring polarization of<br /> gamma-ray photons. The Crab nebula is one of the brightest X-ray / gamma-ray<br /> sources on the sky, and, the only source from which polarized X-ray photons<br /> have been detected. SGD observed the Crab nebula during the initial test<br /> observation phase of Hitomi. We performed the data analysis of the SGD<br /> observation, the SGD background estimation and the SGD Monte Carlo simulations,<br /> and, successfully detected polarized gamma-ray emission from the Crab nebula<br /> with only about 5 ks exposure time. The obtained polarization fraction of the<br /> phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1<br /> $\pm$ 10.6)% and, the polarization angle is 110.7$^o$ + 13.2 / $-$13.0$^o$ in<br /> the energy range of 60--160 keV (The errors correspond to the 1 sigma<br /> deviation). The confidence level of the polarization detection was 99.3%. The<br /> polarization angle measured by SGD is about one sigma deviation with the<br /> projected spin axis of the pulsar, 124.0$^o$ $\pm$0.1$^o$.
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Astrophysical Journal, Supplement Series 238(2) 2018年10月© 2018. The American Astronomical Society. All rights reserved.. We present the third MAXI/GSC catalog in the high Galactic latitude sky () based on the 7-year data from 2009 August 13 to 2016 July 31, complementary to that in the low Galactic latitude sky (|b| > 10°) (Hori et al. 2018). We compile 682 sources detected at significances of s D,4-10 keV ≥ 6.5 in the 4-10 keV band. A two-dimensional image fit based on the Poisson likelihood algorithm (C-statistics) is adopted for the detections and constraints on their fluxes and positions. The 4-10 keV sensitivity reaches ≈0.48 mCrab, or ≈5.9 × 10-12 erg cm-2 s-1, over half of the survey area. Compared with the 37-month Hiroi et al. (2013) catalog, which adopted a threshold of s D,4-10 keV ≥ 7, the source number increases by a factor of ∼1.4. The fluxes in the 3-4 keV and 10-20 keV bands are further estimated, and hardness ratios (HRs) are calculated using the 3-4 keV, 4-10 keV, 3-10 keV, and 10-20 keV band fluxes. We also make the 4-10 keV light curves in 1-year bins for all the sources and characterize their variabilities with an index based on a likelihood function and the excess variance. Possible counterparts are found from five major X-ray survey catalogs by Swift, Uhuru, RXTE, XMM-Newton, and ROSAT, as well as an X-ray galaxy cluster catalog (MCXC). Our catalog provides the fluxes, positions, detection significances, HRs, 1-year bin light curves, variability indices, and counterpart candidates.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(3) 2018年6月 査読有り
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Journal of Astronomical Telescopes, Instruments, and Systems 4(2) 2018年4月 査読有り© The Authors. The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.
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Astrophysical Journal, Supplement Series 235(1) 2018年3月© 2018. The American Astronomical Society. All rights reserved.. We present the first MAXI/GSC X-ray source catalog in the low-Galactic-latitude sky outside the Galactic center region (, l < 30°, and l > 330°) based on 7-year data from 2009 August 13 to 2016 July 31. To overcome source confusion in crowded regions, we have accurately calibrated the position-dependent shape of the point-spread function of the MAXI/GSC by analyzing onboard data. We have also taken into account the Galactic ridge X-ray emission. Using a maximum likelihood image fitting method, we have detected 221 sources with a significance threshold >6.5σ, 7 of which are transients only detected in 73-day time-sliced images. The faintest source has a flux of 5.2 10-12 erg cm-2 s-1 (or an intensity of 0.43 mCrab) in the 4-10 keV band. We have identified the counterparts for about 81% of the detected sources, by cross-matching with the Swift, Uhuru, RXTE, XMM-Newton, MCXC, and ROSAT all-sky survey catalogs. Our catalog contains the source name, position and its error, flux and detection significance in the 3-4 keV, 4-10 keV, and 10-20 keV bands, hardness ratios, and information on the likely counterpart for the individual detected sources. We have obtained 73-day bin light curves of all the cataloged sources over 7 years and have calculated their periodograms. On the basis of the mean properties of time variability and spectral hardness, we suggest that the majority of the unidentified sources are low-mass X-ray binaries or blazars. Finally, we present the log N-log S relations at different Galactic longitudes and for different source populations.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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Publications of the Astronomical Society of Japan 70(2) 2018年3月1日 査読有り© The Author(s) 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2-300 keV band and the Kashima NICT radio telescope in the 1.4-1.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 σ fluctuations of the X-ray fluxes at the pulse peaks, and the 3 σ upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2-300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.5-10 keV and 70-300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) × 10−11 erg cm−2, respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 70(2) 2018年3月 査読有り
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2018年2月14日We present results from the Hitomi X-ray observation of a young<br /> composite-type supernova remnant (SNR) G21.5$-$0.9, whose emission is dominated<br /> by the pulsar wind nebula (PWN) contribution. The X-ray spectra in the 0.8-80<br /> keV range obtained with the Soft X-ray Spectrometer (SXS), Soft X-ray Imager<br /> (SXI) and Hard X-ray Imager (HXI) show a significant break in the continuum as<br /> previously found with the NuSTAR observation. After taking into account all<br /> known emissions from the SNR other than the PWN itself, we find that the Hitomi<br /> spectra can be fitted with a broken power law with photon indices of<br /> $\Gamma_1=1.74\pm0.02$ and $\Gamma_2=2.14\pm0.01$ below and above the break at<br /> $7.1\pm0.3$ keV, which is significantly lower than the NuSTAR result ($\sim9.0$<br /> keV). The spectral break cannot be reproduced by time-dependent particle<br /> injection one-zone spectral energy distribution models, which strongly<br /> indicates that a more complex emission model is needed, as suggested by recent<br /> theoretical models. We also search for narrow emission or absorption lines with<br /> the SXS, and perform a timing analysis of PSR J1833$-$1034 with the HXI and<br /> SGD. No significant pulsation is found from the pulsar. However, unexpectedly,<br /> narrow absorption line features are detected in the SXS data at 4.2345 keV and<br /> 9.296 keV with a significance of 3.65 $\sigma$. While the origin of these<br /> features is not understood, their mere detection opens up a new field of<br /> research and was only possible with the high resolution, sensitivity and<br /> ability to measure extended sources provided by an X-ray microcalorimeter.
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SPACE TELESCOPES AND INSTRUMENTATION 2018: ULTRAVIOLET TO GAMMA RAY 10699 2018年 査読有りThe ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi, "Resolving astrophysical problems by precise high-resolution X-ray spectroscopy".(1) This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission's initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020's and 2030's.Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: "Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects". To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
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NATURE 551(7681) 478-+ 2017年11月 査読有りThe metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae(1). Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode(2-6). Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun(7-11), suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, highresolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations(12-14) disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near-and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment(5,15,16).
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ASTROPHYSICAL JOURNAL 832(2) 2016年12月 査読有りWe present multi-epoch X-ray spectral observations of three Type IIn supernovae (SNe), SN 2005kd, SN 2006jd, and SN 2010jl, acquired with Chandra, XMM-Newton, Suzaku, and Swift. Previous extensive X-ray studies of SN. 2010jl have revealed that X-ray spectra are dominated by thermal emission, which likely arises from a hot plasma heated by a forward shock propagating into a massive circumstellar medium (CSM). Interestingly, an additional soft X-ray component was required to reproduce the spectra at a period of similar to 1-2 years after the SN explosion. Although this component is likely associated with the SN, its origin remained an open question. We find a similar, additional soft X-ray component from the other two SNe IIn as well. Given this finding, we present a new interpretation for the origin of this component; it is thermal emission from a forward shock essentially identical to the hard X-ray component, but directly reaches us from a void of the dense CSM. Namely, the hard and soft components are responsible for the heavily and moderately absorbed components, respectively. The co-existence of the two components with distinct absorptions as well as the delayed emergence of the moderately absorbed X-ray component could be evidence for asphericity of the CSM. We show that the X-ray spectral evolution can be qualitatively explained by considering a torus-like geometry for the dense CSM. Based on our X-ray spectral analyses, we estimate the radius of the torus-like CSM to be on the order of similar to 5 x 10(16) cm.
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Publications of the Astronomical Society of Japan 68(5) 2016年10月1日 査読有り© 2016 The Author. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved. Twenty-three giant flares from thirteen active stars (eight RS CVn systems, one Algol system, three dMe stars, and one young stellar object) were detected during the first two years of our all-sky X-ray monitoring with the gas propotional counters (GSC) of the Monitor of All-sky X-ray Image (MAXI). The observed parameters of all these MAXI/GSC flares are found to be at the upper ends for stellar flares with the luminosity of 1031-34 erg s-1 in the 2-20 keV band, the emission measure of 1054-57 cm-3, the e-folding time of 1 hr to 1.5 d, and the total radiative energy released during the flare of 1034-39 erg. Notably, the peak X-ray luminosity of 5+4-2 × 1033erg s-1 in the 2-20 keV band was detected in one of the flares on II Peg, which is one of the, or potentially the, largest-ever-observed in stellar flares. X-ray flares were detected from GT Mus, V841 Cen, SZ Psc, and TWA-7 for the first time in this survey. Whereas most of our detected sources are multiple-star systems, two of them are single stars (YZ CMi and TWA-7). Among the stellar sources within 100 pc distance, the MAXI/GSC sources have larger rotation velocities than the other sources. This suggests that the rapid rotation velocity may play a key role in generating large flares. Combining the X-ray flare data of nearby stars and the sun, taken from literature and our own data, we discovered a universal correlation of τ LX0.2 for the flare duration τ and the intrinsic X-ray luminosity LX in the 0.1-100 keV band, which holds for 5 and 12 orders of magnitude in τ and LX, respectively. The MAXI/GSC sample is located at the highest ends of the correlation.
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ApJ, 837, L15 (2017) 837 2016年7月26日High-resolution X-ray spectroscopy with Hitomi was expected to resolve the<br /> origin of the faint unidentified E=3.5 keV emission line reported in several<br /> low-resolution studies of various massive systems, such as galaxies and<br /> clusters, including the Perseus cluster. We have analyzed the Hitomi<br /> first-light observation of the Perseus cluster. The emission line expected for<br /> Perseus based on the XMM-Newton signal from the large cluster sample under the<br /> dark matter decay scenario is too faint to be detectable in the Hitomi data.<br /> However, the previously reported 3.5 keV flux from Perseus was anomalously high<br /> compared to the sample-based prediction. We find no unidentified line at the<br /> reported high flux level. Taking into account the XMM measurement uncertainties<br /> for this region, the inconsistency with Hitomi is at a 99% significance for a<br /> broad dark-matter line and at 99.7% for a narrow line from the gas. We do not<br /> find anomalously high fluxes of the nearby faint K line or the Ar satellite<br /> line that were proposed as explanations for the earlier 3.5 keV detections. We<br /> do find a hint of a broad excess near the energies of high-n transitions of<br /> Sxvi (E=3.44 keV rest-frame) -- a possible signature of charge exchange in the<br /> molecular nebula and another proposed explanation for the unidentified line.<br /> While its energy is consistent with XMM pn detections, it is unlikely to<br /> explain the MOS signal. A confirmation of this interesting feature has to wait<br /> for a more sensitive observation with a future calorimeter experiment.
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NATURE 535(7610) 117-+ 2016年7月 査読有りClusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes(1) of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling-a process known as active galactic nucleus feedback(2-6). Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 +/- 10 kilometres per second in the region 30-60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 +/- 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.
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SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY 9905 2016年 査読有り
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Publications of the Astronomical Society of Japan 67(6) p.121 2015年12月Suzaku observations of the Wolf-Rayet binary WR 140 (WC7pd+O5.5fc) were made<br /> at four different times around periastron passage in 2009 January. The spectra<br /> changed in shape and flux with the phase. As periastron approached, the column<br /> density of the low-energy absorption increased, which indicates that the<br /> emission from the wind-wind collision plasma was absorbed by the dense W-R<br /> wind. The spectra can be mostly fitted with two different components: a warm<br /> component with kT=0.3--0.6 keV and a dominant hot component with kT~3 keV. The<br /> emission measure of the dominant, hot component is not inversely proportional<br /> to the distance between the two stars. This can be explained by the O star wind<br /> colliding before it has reached its terminal velocity, leading to a reduction<br /> in its wind momentum flux. At phases closer to periastron, we discovered a cool<br /> plasma component in a recombining phase, which is less absorbed. This component<br /> may be a relic of the wind-wind collision plasma, which was cooled down by<br /> radiation, and may represent a transitional stage in dust formation.
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Société Royale des Sciences de Liège, Bulletin 80 724-728 2011年1月
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ASTRONOMY & ASTROPHYSICS 490(1) 259-264 2008年10月We present XMM-Newton observations of the WC binary theta Muscae (WR 48), the second brightest Wolf-Rayet binary in optical wavelengths. The system consists of a short-period (19.1375 days) WC5/WC6 + O6/O7V binary and possibly has an additional O supergiant companion (O9.5/B0Iab) which is optically identified at a separation of similar to 46 mas. Strong emission lines from highly ionized ions of C, O, Ne, Mg, Si, S, Ar, Ca and Fe are detected. The spectra are fitted by a multi-temperature thin-thermal plasma model with an interstellar absorption N(H) = 2-3 x 10(21) cm(-2). Lack of nitrogen line indicates that the abundance of carbon is at least an order of magnitude larger than that of nitrogen. A Doppler shift of similar to 630 km s(-1) is detected for the O VIII line, while similar shifts are obtained from the other lines. The reddening strongly suggests that the emission lines originated from the wind-wind shock zone, where the average velocity is similar to 600 km s(-1). The red-shift motion is inconsistent with a scenario in which the X-rays originate from the wind-wind collision zone in the short-period binary, and would be evidence supporting the widely separated O supergiant as a companion. This may make up the collision zone be lying behind the short-period binary. In addition to the emission lines, we also detected the RRC (radiative recombination continuum) structure from carbon around 0.49 keV. This implies the existence of additional cooler plasma.
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PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 60 S49-S56 2008年2月 査読有りWe report on a serendipitous detection of an intense X-ray flare from the Tycho reference source on HD 161084 during a Suzaku observation of the galactic center region for similar to 20 ks. The X-ray Imaging Spectrometer recorded a flare from this A1-type dwarf or subgiant star with a flux of similar to 1.4 x 10(-12) erg s(-1) cm(-2) (0.5-10 keV) and a decay time scale of similar to 0.5 hr. The spectrum is hard with a prominent Fe XXV K alpha emission line at 6.7 keV, which is explained by a similar to 5 keV thin-thermal plasma model attenuated by a similar to 1.4 x 10(21) cm(-2) extinction. The low extinction, which is consistent with the optical reddening, indicates that the source is a foreground star toward the galactic center region. Based on a spectroscopic parallax distance of similar to 530 pc, the peak X-ray luminosity amounts to similar to 1 x 10(32) erg s(-1) (0.5-10 keV). This is much larger than the X-ray luminosity of ordinary late-type main-sequence stars, and the X-ray emission is unattributable to a hidden late-type companion that comprises a wide binary system with the A star. We discuss possible nature of HD 161084, and suggest that it is most likely an interacting binary with elevated magnetic activity in the companion, such as the Algol-type system. The flux detected by Suzaku during the burst is similar to 100-times larger than the quiescent level measured using the archived XMM-Newton and Chandra data. The large flux amplification makes this star a unique example among sources of this class.
MISC
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Proceedings of Science 2017年1月1日© Copyright owned by the author(s) under the terms of the Creative Commons. Since the launch in 2009 August, with the unprecedentedly high sensitivity as an all-sky X-ray monitor, MAXI has caught more than a hundred of huge flares from stars. Most of them are from low-mass, active stars (RS CVn systems, an Algol system, dMe systems, a dKe system, Young Stellar Objects). With the total radiative energy of 1034–1039ergs, the MAXI detections have broken the record of the largest flaring magnitudes in each stellar categories. The enlarged sample of intense flares has enabled us to do systematic studies in various viewpoints. One of the studies is the discovery of a universal correlation between the flare duration and the intrinsic X-ray luminosity, which holds for 5 and 12 orders of magnitude in the duration and LX, respectively (Tsuboi et al. 2016). Here, we review the studies of stellar flares obtained with MAXI.
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2015年11月4日Colliding Wolf-Rayet (WR) winds produce thermal X-ray emission widely<br /> observed by X-ray telescopes. In wide WR+O binaries, such as WR 140, the X-ray<br /> flux is tied to the orbital phase, and is a direct probe of the winds'<br /> properties. In the Galactic center, $\sim$30 WRs orbit the super massive black<br /> hole (SMBH) within $\sim$10", leading to a smorgasbord of wind-wind collisions.<br /> To model the X-ray emission of WR 140 and the Galactic center, we perform 3D<br /> hydrodynamic simulations to trace the complex gaseous flows, and then carry out<br /> 3D radiative transfer calculations to compute the variable X-ray spectra. The<br /> model WR 140 RXTE light curve matches the data well for all phases except the<br /> X-ray minimum associated with periastron, while the model spectra agree with<br /> the RXTE hardness ratio and the shape of the Suzaku observations throughout the<br /> orbit. The Galactic center model of the Chandra flux and spectral shape match<br /> well in the region r$<$3", but the model flux falls off too rapidly beyond this<br /> radius.
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Suzaku-MAXI 2014: Expanding the Frontiers of the X-ray Universe pp.pp220-221 2014年9月
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Suzaku-MAXI 2014: Expanding the Frontiers of the X-ray Universe pp.pp208-209 2014年9月
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Suzaku-MAXI 2014: Expanding the Frontiers of the X-ray Universe pp.pp164-165 2014年9月
講演・口頭発表等
68所属学協会
3Works(作品等)
1共同研究・競争的資金等の研究課題
3-
科学研究費補助金 若手研究(B) 2016年4月 - 2019年3月
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科学研究費補助金 特別研究促進費 2009年4月 - 2011年3月
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2005年
