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

作者：Liu JF^*; Bregman JN; Lloyd Davies E; Irwin J; Espaillat C; Seitzer P

来源：Astrophysical Journal, 2005, 621(1): L17-L20.

DOI：10.1086/428902

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

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.

• 出版日期2005-3-1