THE LOW-SPIN BLACK HOLE IN LMC X-3

Building upon a new dynamical model for the X-ray binary LMC X-3, we measure the spin of its black hole (BH) primary via the continuum-fitting method. We consider over one thousand thermal-state Rossi X-ray Timing Explorer X-ray spectra of LMC X-3. Using a large subset of these spectra, we constrain the spin parameter of the BH to be a(*) = 0.25(-0.29)(+0.20) (90% confidence). Our estimate of the uncertainty in a(*) takes into account a wide range of systematic errors. We discuss evidence for a correlation between a BH's spin and the complexity of its X-ray spectrum.