X-RAY SPECTRAL STATE IS NOT CORRELATED WITH LUMINOSITY IN HOLMBERG II X-1

被引：32

作者：

Grise, F. ^{[1
]}

Kaaret, P. ^{[1
]}

Feng, H. ^{[2
,3
]}

Kajava, J. J. E. ^{[4
]}

Farrell, S. A. ^{[5
]}

机构：

[1] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA

[2] Tsinghua Univ, Dept Engn Phys, Beijing 100084, Peoples R China

[3] Tsinghua Univ, Ctr Astrophys, Beijing 100084, Peoples R China

[4] Univ Oulu, Astron Div, Dept Phys, Oulu 90014, Finland

[5] Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England

来源：

ASTROPHYSICAL JOURNAL LETTERS | 2010年 / 724卷 / 02期

关键词：

accretion; accretion disks; black hole physics; X-rays: binaries; X-rays: individual (Holmberg II X-1); BLACK-HOLE BINARIES; GRS 1915+105; ESO; 243-49; GALAXY; VARIABILITY; TRANSITIONS; EVOLUTION; EMISSION; MASSES; PERIOD;

D O I：

10.1088/2041-8205/724/2/L148

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

The ultraluminous X-ray source (ULX) Holmberg II X-1 has been observed over four months in 2009/2010 by the Swift observatory. The source luminosity varied by a factor of up to 14, reaching a maximum 0.3-10 keV luminosity of similar to 3.0 x 10(40) erg s(-1). The spectral properties do not vary much over these four months, with only a slight monotonic increase of the hardness ratio with the count rate. This means that the erratic flaring activity of the source is not associated with spectral changes, as seen in other ULXs. Conversely, comparison with data obtained by Swift in 2006 shows a completely different picture: while at a luminosity also seen in the 2009/2010 data, the source appears with a hard spectrum. Thus, it appears that, as in Galactic black hole binaries, spectral states in this ULX are not determined only by the X-ray luminosity.

引用

页码：L148 / L152

页数：5

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