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ID 20651
file
creator
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
subject
accretion, accretion disks
black hole physics
X-rays: individual (NGC 1313 X-1, NGC 1313 X-2)
NDC
Astronomy. Space sciences
abstract
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.
journal title
Publications of the Astronomical Society of Japan
volume
Volume 59
start page
S257
end page
S267
date of issued
2007-01-25
publisher
日本天文学会
issn
0004-6264
ncid
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
Copyright (c) 2007 Astronomical Society of Japan
relation url
department
Graduate School of Science