THE MASS OF THE BLACK HOLE IN LMC X-3

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 kms(-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-rot sin i = 118.5 +/- 6.6 kms(-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 degrees.84 +/- 0 degrees.37 for models that do not include X-ray heating and an inclination of i = 69 degrees.24 +/- 0 degrees.72 for models that incorporate X-ray heating. Adopting the latter inclination measurement, we find masses of 3.63 +/- 0.57 M-circle dot and 6.98 +/- 0.56 M-circle dot for the companion star and the black hole, respectively. We briefly compare our results with earlier work and discuss some of their implications.