2005ApJ...621L..17L -
Astrophys. J., 621, L17-L20 (2005/March-1)
A 2 hour quasi period in an ultraluminous X-ray source in NGC 628.
LIU J.-F., BREGMAN J.N., LLOYD-DAVIES E.J., IRWIN J., ESPAILLAT C. and SEITZER P.
Abstract (from CDS):
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 ~(2-20)x103 M☉is estimated from the fb-Møscaling relation found in the Galactic X-ray binaries and active galactic nuclei.
Abstract Copyright:
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Journal keyword(s):
Galaxies: Individual: NGC Number: NGC 628 - X-Rays: Binaries
Simbad objects:
12
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