Astrophys. J., 697, 573-591 (2009/May-3)
A new dynamical model for the black hole binary LMC X-1.
OROSZ J.A., STEEGHS D., McCLINTOCK J.E., TORRES M.A.P., BOCHKOV I., GOU L., NARAYAN R., BLASCHAK M., LEVINE A.M., REMILLARD R.A., BAILYN C.D., DWYER M.M. and BUXTON M.
Abstract (from CDS):
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 R2= 17.0±0.8 R☉ and a projected rotational velocity of Vrot sin i = 129.9±2.2 km/s. Using these measured properties to constrain the dynamical model, we find an inclination of i = 36°.38 ±1°.92, a secondary star mass of M2= 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.
binaries: spectroscopic - black hole physics - stars: early-type - X-rays: binaries - X-rays: individual: LMC X-1
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