A NEW DYNAMICAL MODEL FOR THE BLACK HOLE BINARY LMC X-1
Author(s)Orosz, Jerome A.; Steeghs, Danny; McClintock, Jeffrey E.; Torres, Manuel A. P.; Bochkov, Ivan; Gou, Lijun; Narayan, Ramesh; Blaschak, Michael; Bailyn, Charles D.; Dwyer, Morgan; Buxton, Michelle; Levine, Alan M; Remillard, Ronald A; ... Show more Show less
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We present a dynamical model of the high mass X-ray binary LMC X-1 based on high-resolution optical spectroscopy and extensive optical and near-infrared photometry. From our new optical data we find an orbital period of P = 3.90917 ± 0.00005 days. We present a refined analysis of the All Sky Monitor data from RXTE and find an X-ray period of P = 3.9094 ± 0.0008 days, which is consistent with the optical period. A simple model of Thomson scattering in the stellar wind can account for the modulation seen in the X-ray light curves. The V – K color of the star (1.17 ± 0.05) implies AV = 2.28 ± 0.06, which is much larger than previously assumed. For the secondary star, we measure a radius of R 2 = 17.0 ± 0.8 R ☉ and a projected rotational velocity of V rotsin i = 129.9 ± 2.2 km s–1. Using these measured properties to constrain the dynamical model, we find an inclination of i = 36fdg38 ± 1fdg92, a secondary star mass of M 2 = 31.79 ± 3.48 M ☉, and a black hole mass of 10.91 ± 1.41 M ☉. The present location of the secondary star in a temperature-luminosity diagram is consistent with that of a star with an initial mass of 35 M ☉ that is 5 Myr past the zero-age main sequence. The star nearly fills its Roche lobe (≈90% or more), and owing to the rapid change in radius with time in its present evolutionary state, it will encounter its Roche lobe and begin rapid and possibly unstable mass transfer on a timescale of a few hundred thousand years.
DepartmentMIT Kavli Institute for Astrophysics and Space Research
Institute of Physics/American Astronomical Society
Orosz, Jerome A., Danny Steeghs, Jeffrey E. McClintock, Manuel A. P. Torres, Ivan Bochkov, Lijun Gou, Ramesh Narayan, et al. “A NEW DYNAMICAL MODEL FOR THE BLACK HOLE BINARY LMC X-1.” The Astrophysical Journal 697, no. 1 (May 4, 2009): 573–591. © 2009 American Astronomical Society.
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