The mass of the black hole in LMC X-3

Abstract

We analyze a large set of new and archival photometric and spectroscopic observations of LMC X-3 to arrive at a self-consistent dynamical model for the system. Using echelle spectra obtained with the Magellan Inamori Kyocera Echelle instrument on the 6.5 m Magellan Clay telescope and the UVES instrument on the second 8.2 m Very Large Telescope, we find a velocity semiamplitude for the secondary star of K 2 = 241.1 ± 6.2 km s-1, where the uncertainty includes an estimate of the systematic error caused by X-ray heating. Using the spectra, we also find a projected rotational velocity of V rotsin i = 118.5 ± 6.6 km s-1. From an analysis of archival B and V light curves as well as new B and V light curves from the SMARTS 1.3 m telescope, we find an inclination of i = 69.°84 ± 0.°37 for models that do not include X-ray heating and an inclination of i = 69.°24 ± 0.°72 for models that incorporate X-ray heating. Adopting the latter inclination measurement, we find masses of 3.63 ± 0.57 M and 6.98 ± 0.56 M for the companion star and the black hole, respectively. We briefly compare our results with earlier work and discuss some of their implications.