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Modeling the low-state spectrum of the X-Ray nova XTE J1118+480

Esin, Ann A.; McClintock, Jeffrey E.; Drake, Jeremy J.; Garcia, Michael R.; Haswell, Carole A.; Hynes, Robert I. and Muno, Michael P. (2001). Modeling the low-state spectrum of the X-Ray nova XTE J1118+480. Astrophysical Journal, 555(number 1, part 1) pp. 483–488.

URL: http://www.journals.uchicago.edu/ApJ/journal/issue...
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Abstract

Based on recent multiwavelength observations of the new X-ray nova XTE J1118+480, we can place strong constraints on the geometry of the accretion flow in which a low/hard-state spectrum, characteristic of an accreting black hole binary, is produced. We argue that the absence of any soft blackbody-like component in the X-ray band implies the existence of an extended hot optically thin region, with the optically thick cool disk truncated at some radius Rtr 55RSchw. We show that such a model can indeed reproduce the main features of the observed spectrum: the relatively high optical to X-ray ratio, the sharp downturn in the far-UV band, and the hard X-ray spectrum. The absence of the disk blackbody component also underscores the requirement that the seed photons for thermal Comptonization be produced locally in the hot flow, e.g., via synchrotron radiation. We attribute the observed spectral break at 2 keV to absorption in a warm, partially ionized gas.

Item Type: Journal Article
ISSN: 1538-4357
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 4365
Depositing User: Users 6827 not found.
Date Deposited: 06 Jul 2006
Last Modified: 02 Dec 2010 19:51
URI: http://oro.open.ac.uk/id/eprint/4365
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