8th HEAD Meeting, 8-11 September, 2004
Session 15 Black Holes Binaries and Intermediate Mass Black Holes
Poster, Thursday, September 9, 2004, 9:00am-10:00pm

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[15.12] Black Hole X-ray Binary LMC~X--1 and LMC~X--3: Observations Confront Spectral Models

Y. Yao, Q. D. Wang (UMASS), S. N. Zhang (UAH)

We present a comprehensive spectral analysis of black hole X-ray binaries, LMC X--1 and LMC X--3, based on BeppoSAX observations. We test both the commonly-used multi-color disk plus power law (MCD+PL) model and a newly-developed Monte-Carlo simulation-based Comptonized multi-color disk (CMCD) model, by comparing the inferred parameters with independent measurements. While both model give an adequate description of the spectra, we find a significant discrepancy between the MCD+PL inferred X-ray-absorbing gas column density and the absorption-edge measurement based on dispersed X-ray spectra. The MCD+PL fits to the LMC X-1 spectra also require a change in the inner disk radius during the BeppoSAX observation, which may be due to the nonphysical effects inherited in the model. No similar problem is found for the CMCD model. The inferred black hole masses, ~ 6.8(6.5-7.8) solar mass for LMC X--1 and ~ 7.2(7.1 - 7.3) solar mass for LMC X--3 (90% confidence limits), and the disk inclination angles, <= 43 degree and <= 69 degree, are all consistent with the optical measurements. The obtained X-ray-absorbing column density, 0.45(0.42 - 0.47) x 1021 cm-2 for LMC X--3, is statistically consistent with the value derived from the X-ray-absorption edge measurement. The spectral state evolution of LMC X--1 within the BeppoSAX observation can naturally be explained by a change in the accretion rate, which leads to an increase in both the inner disk temperature and the Comptonization opacity.

The author(s) of this abstract have provided an email address for comments about the abstract: yaoys@astro.umass.edu

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.