Suzaku observation of two ultraluminous X-ray sources in NGC 1313

Publications of the Astronomical Society of Japan 59 巻 S257-S267 頁 2007-01-25 発行
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タイトル ( eng )
Suzaku observation of two ultraluminous X-ray sources in NGC 1313
作成者
Miyawaki Ryohei
Ebisawa Ken
Kubota Aya
Miyamoto Masao
Winter Lisa M.
Ueda Yoshihiro
Dewangan Gulab C.
Done Chris
Griffiths Richard E.
Haba Yoshito
Kokubun Motohide
Kotoku Jun'ichi
Makishima Kazuo
Matsushita Kyoko
Mushotzky Ricard F.
Namiki Masaaki
Petre Robert
Tamagawa Toru
Terashima Yuichi
収録物名
Publications of the Astronomical Society of Japan
59
開始ページ S257
終了ページ S267
抄録
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.
著者キーワード
accretion, accretion disks
black hole physics
X-rays: individual (NGC 1313 X-1, NGC 1313 X-2)
NDC分類
天文学・宇宙科学 [ 440 ]
言語
英語
資源タイプ 学術雑誌論文
出版者
日本天文学会
発行日 2007-01-25
権利情報
Copyright (c) 2007 Astronomical Society of Japan
出版タイプ Version of Record(出版社版。早期公開を含む)
アクセス権 オープンアクセス
収録物識別子
[ISSN] 0004-6264
[NCID] AA1082896X
[URI] http://pasj.asj.or.jp/v59/sp1/59s122/59s122a.html