著者

Tamagawa Toru Hayato Asami Nakamura Satoshi TERADA Yukikatsu BAMBA Aya HIRAGA Junko S. HUGHES John P. HWANG Una KATAOKA Jun KINUGASA Kenzo KUNIEDA Hideyo TANAKA Takaaki TSUNEMI Hiroshi UENO Masaru HOLT Stephen S. KOKUBUN Motohide MIYATA Emi SZYMKOWIAK Andrew TAKAHASHI Tadayuki TAMURA Keisuke UENO Daisuke MAKISHIMA Kazuo

出版者

社団法人日本天文学会

雑誌

PASJ : publications of the Astronomical Society of Japan (ISSN:00046264)

巻号頁・発行日

vol.61, no.1, pp.S167-S174, 2009-01-30

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

著者

Mizuno Tsunefumi Miyawaki Ryohei Ebisawa Ken KUBOTA Aya MIYAMOTO Masao WINTER Lisa UEDA Yoshihiro ISOBE Naoki MAKISHIMA Kazuo

出版者

Published for the Yukawa Institute for Theoretical Physics and the Physical Society of Japan

雑誌

Progress of theoretical physics. Supplement (ISSN:03759687)

巻号頁・発行日

no.169, pp.229-233, 2007-12-19

参考文献数

24

被引用文献数

1

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We report about the Suzaku observation of two ultraluminous X-ray sources (ULXs), X-1 and X-2, in NGC1313, together with their spectra by XMM-Newton. During the observation, both showed intensity-correlated spectral changes. The brighter source, X-1, exhibited the highest luminosity (~3×10^<40>erg s^<-1>) ever recorded from this source. Its spectral variation is ascribed to a strong power-law like component with a mild high energy curvature, while about 10% of the flux is carried by a stable soft component modeled by a cool disk emission. These properties suggest that the source was in the "very high" state, wherein the disk emission is strongly Comptonized and the optically-thick disk is truncated at a large radii or cooled off. The spectrum of X-2 is best represented, in its fainter phase, by a multicolor disk model with the innermost disk temperature of 1.2-1.3keV, and becomes flatter as the source gets brighter. Hence X-2 is interpreted to be in a slim disk state. These results suggest that the two ULXs host black holes of a few tens to a few hundreds solar masses.

著者

Mizuno Tsunefumi Miyawaki Ryohei Ebisawa Ken KUBOTA Aya MIYAMOTO Masao WINTER Lisa M. UEDA Yoshihiro ISOBE Naoki DEWANGAN Gulab C. DONE Chris GRIFFITHS Richard E. HABA Yoshito KOKUBUN Motohide KOTOKU Jun'ichi MAKISHIMA Kazuo MATSUSHITA Kyoko MUSHOTZKY Richard F. NAMIKI Masaaki PETRE Robert TAKAHASHI Hiromitsu TAMAGAWA Toru TERASHIMA Yuichi

出版者

日本天文学会

雑誌

PASJ : publications of the Astronomical Society of Japan (ISSN:00046264)

巻号頁・発行日

vol.59, no.1, pp.S257-S267, 2007-01-31

参考文献数

56

被引用文献数

2

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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.