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titleSuzaku detections of luminosity-dependent spectral changes from the two ultraluminous X-ray sources, X1 and X2, in NGC 1313
Author(jpn)磯部, 直樹; 大須賀, 健; 牧島, 一夫; 水野, 恒史; 久保田, あや
Author(eng)Isobe, Naoki; Ohsuga, Ken; Makishima, Kazuo; Mizuno, Tsunefumi; Kubota, Aya; Gandhi, Poshak
Author Affiliation(jpn)京都大学理学研究科宇宙物理学教室; 国立天文台; 理化学研究所; 広島大学理学部; 芝浦工業大学システム工学部電子情報システム学科; 理化学研究所
Author Affiliation(eng)Department of Astronomy, Kyoto University; National Astronomical Observatory of Japan; Cosmic Radiation Laboratory, RIKEN; Department of Physics, Hiroshima University; Department of Electronic Information System, Shibaura Institute of Technology; Cosmic Radiation Laboratory, RIKEN
Issue Date2010-02-26
Japan Aerospace Exploration Agency (JAXA)
Publication title宇宙航空研究開発機構特別資料:
JAXA Special Publication: The Energetic Cosmos; from Suzaku to ASTRO-H
Start page260
End page263
Publication date2010-02-26
AbstractA Suzaku follow-up observation of the nearby galaxy NGC 1313 was performed on 2008 December 5-8. The 0.5 - 10 keV luminosity of the two ultraluminous X-ray sources (ULXs), X1 and X2, in the galaxy was measured as 7.1 x 10(exp 39) ergs s(exp -1) and 1.9 x 10(exp 39) ergs s(exp -1), respectively, both of which are by a factor of 4 lower than those of the scientific working group (SWG) observation in 2005. The X-ray spectrum of X1 is described with a composite model, consisting of a power-law (PL) component with a high energy cut off and a cool accretion disk emission. In comparison with the SWG observation, the innermost disk temperature stayed relatively unchanged (T(sub in) approximately 0.25 keV), while the cut off energy became slightly higher (E(sub cut) = 6.88(sup +4.9)(sub -2.2) keV). On the other hand, X2 exhibited a transition from the disk-like spectrum to the PL-dominated one with a photon index of gamma = 1.84(sup +0.15)(sub -0.19), between the SWG and this follow-up observations. These results re-confirmed that the spectral properties of these two ULXs are successfully interpreted, on the basis of the very high and slim disk states of Galactic black holes at the sub- or trans-Eddington luminosities. As a result, the intermediate-mass-black-hole interpretation for ULXs are supported.
DescriptionMeeting Information: The 3rd Suzaku international Conference "Energetic Cosmos : from Suzaku to ASTRO-H" (June 29-July 2, 2009. Grand Park Otaru Hotel), Otaru, Hokkaido Japan
Meeting sponsors: The University of Tokyo, The Institute of Physical and Chemical Research, The Japan Society for the Promotion of Science
Keywordsaccretion, accretion disks - black hole physics - galaxies: individual (NGC 1313)
Document TypeConference Paper
JAXA Category特別資料
Report NoJAXA-SP-09-008E

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