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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
The spectral energy distribution of quiescent black hole X-ray binaries: New constraints from Spitzer
Astrophysical Journal, Volume 670, No. 1, Year 2007
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Description
Among the various issues that remain open in the field of accretion onto black hole X-ray binaries (BHBs) is the question of how gas accretes at very low Eddington ratios, in the so-called quiescent regime. While there is general agreement that X-rays are produced by a population of high-energy electrons near the BH, there is controversy concerning the modeling of the contributions of inflowing versus outflowing particles and their relative energy budget. Recent Spitzer observations of three quiescent BHBs have shown evidence for excess emission with respect to the Rayleigh-Jeans tail of the companion star between 8-24 μm. We suggest that synchrotron emission from a partially self-absorbed outflow might be responsible for the observed mid-IR excess, in place of, or in addition to, thermal emission from circumbinary material. If so, then the jet synchrotron luminosity, integrated from radio to near-IR frequencies, exceeds the measured 2-10 keV luminosity by a factor of a few in these systems. In turn, the mechanical power stored in the jet exceeds the bolometric X-ray luminosity by at least 4 orders of magnitude. We compile the broadband spectral energy distribution (SED) of A0620-00, the lowest Eddington-ratio stellar mass BH with a known radio counterpart, by means of simultaneous radio, optical, and X-ray observations, and the archival Spitzer data. We are able to fit the SED of A0620-00 with a maximally jet-dominated model, in which the radio through the soft X-rays are dominated by synchrotron emission, while the hard X-rays are dominated by inverse Compton at the jet base. The fitted parameters land in a range of values reminiscent of the Galactic center supermassive black hole Sgr A*. Most notably, the inferred ratio of the jet acceleration rate to local cooling rates is 2 orders of magnitude weaker than higher luminosity, hard-state sources. © 2007. The American Astronomical Society. All rights reserved.
Authors & Co-Authors
Gallo, Elena
United States, Santa Barbara
University of California, Santa Barbara
Migliari, Simone
United States, La Jolla
University of California, San Diego
Markoff, Sera B.
Netherlands, Amsterdam
Universiteit Van Amsterdam
Tomsick, John A.
United States, Berkeley
University of California, Berkeley
Bailyn, Charles D.
United States, New Haven
Yale University
Berta, Stefano
United States, La Jolla
University of California, San Diego
Italy, Padua
Università Degli Studi Di Padova
Fender, Robert P.
United Kingdom, Southampton
University of Southampton
Miller-Jones, James C.A.
Netherlands, Amsterdam
Universiteit Van Amsterdam
Statistics
Citations: 86
Authors: 8
Affiliations: 7
Identifiers
Doi:
10.1086/521524
ISSN:
0004637X
Research Areas
Environmental
Study Design
Cross Sectional Study