A 2 hour quasi period in an ultraluminous X-ray source in NGC 628

被引：21

作者：

Liu, JF ^{[1
]}

Bregman, JN ^{[1
]}

Lloyd-Davies, E ^{[1
]}

Irwin, J ^{[1
]}

Espaillat, C ^{[1
]}

Seitzer, P ^{[1
]}

机构：

[1] Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA

来源：

ASTROPHYSICAL JOURNAL | 2005年 / 621卷 / 01期

关键词：

galaxies : individual (NGC 628); X-rays : binaries;

D O I：

10.1086/428902

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Quasi-periodic oscillations and X-ray spectroscopy are powerful probes of black hole masses and accretion disks, and here we apply these diagnostics to an ultraluminous X-ray source (ULX) in the spiral galaxy NGC 628 (M74). This object was observed four times over 2 years with the Chandra X-Ray Observatory and XMM-Newton, with three long observations showing dramatic variability, distinguished by a series of outbursts with a quasi period of 4000-7000 s. This is unique behavior among ULXs and Galactic X-ray binaries because of the combination of its burstlike peaks and deep troughs, its long quasi periods, its high variation amplitudes of >90%, and its substantial variability between observations. The X-ray spectra is fitted by an absorbed accretion disk plus a power-law component, suggesting the ULX was in a spectral state analogous to the low/hard state or the very high state of Galactic black hole X-ray binaries. A black hole mass of similar to(2-20) x 10(3) M-circle dot is estimated from the f(b)-M-circle scaling relation found in the Galactic X- ray binaries and active galactic nuclei.

引用

页码：L17 / L20

页数：4