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ID 34756
本文ファイル
著者
Sakurai, Soki
Makishima, Kazuo
キーワード
binaries: general
stars: individual (4U 1608-522)
stars: neutron
X-rays: stars
NDC
天文学・宇宙科学
抄録(英)
To investigate the physics of mass accretion onto weakly magnetized neutron stars (NSs), 95 archival Rossi X-Ray Timing Explorer data sets of an atoll source 4U 1608-522, acquired over 1996-2004 in the so-called upper-banana state, were analyzed. The object meantime exhibited 3-30 keV luminosity in the range of less than or similar to 10(35)-4 x 10(37) erg s(-1), assuming a distance of 3.6 kpc. The 3-30 keV Proportional Counter Array spectra, produced one from each data set, were represented successfully with a combination of a soft and a hard component, the presence of which was revealed in a model-independent manner by studying spectral variations among the observations. The soft component is expressed by the so-called multi-color disk model with a temperature of similar to 1.8 keV, and is attributed to the emission from an optically thick standard accretion disk. The hard component is a blackbody (BB) emission with a temperature of similar to 2.7 keV, thought to be emitted from the NS surface. As the total luminosity increases, a continuous decrease is observed in the ratio of the BB luminosity to that of the disk component. This property suggests that it gradually becomes difficult for the matter flowing through the accretion disk to reach the NS surface, presumably forming outflows driven by the increased radiation pressure. On timescales of hours to days, the overall source variability was found to be controlled by two independent variables: the mass accretion rate and the innermost disk radius, which changes both physically and artificially.
掲載誌名
Astrophysical Journal
738巻
1号
開始ページ
62
出版年月日
2011
出版者
IOP science
ISSN
0004-637X
NCID
出版者DOI
言語
英語
NII資源タイプ
学術雑誌論文
広大資料タイプ
学術雑誌論文
DCMIタイプ
text
フォーマット
application/pdf
著者版フラグ
publisher
権利情報
(c) 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
関連情報URL
部局名
理学研究科