Paper: astro-ph/0605190
Date: Mon, 8 May 2006 01:59:05 GMT (85kb)

Title: A Prominent Accretion Disk in the Low-Hard State of the Black Hole
Candidate SWIFT J1753.5-0127

Authors: J. M. Miller (1), J. Homan (2), G. Miniutti (3) ((1) University of
Michigan, (2) MIT, (3) University of Cambridge)

Comments: 4 pages, 3 figures, submitted to ApJ
\\
We report on simultaneous XMM-Newton and RXTE observations of the
stellar-mass black hole candidate SWIFT J1753.5-0127. The source was observed
in the "low-hard" state, during the decline of a hard ouburst. The inner
accretion disk is commonly assumed to be radially truncated in this state, and
it has been suggested that this property may be tied to the production of
steady, compact jets. Fits to the X-ray spectra of SWIFT J1753.5-0127 with a
number of simple models clearly reveal a cool (kT = 0.2 keV) accretion disk.
The disk component is required at more than the 8 sigma level of confidence.
Although estimates of inner disk radii based on continuum spectroscopy are
subject to considerable uncertainty, fits with a number of models suggest that
the disk is observed at or close to the innermost stable circular orbit.
Recently, an observation of GX 339-4 revealed a disk extending to the innermost
stable circular orbit at L_X = 0.05 L_Edd; our results from SWIFT J1753.5-0127
extend this finding down to L_X = 0.003 (d/8.5 kpc)^2 (M/10 Msun) L_Edd. We
discuss our results within the context of low-luminosity accretion flow models
and disk-jet connections.

\\ ( http://arXiv.org/abs/astro-ph/0605190 , 85kb)