Steiner, JamesMcClintock, JeffreyRemillard, Ronald A.Gou, LijunYamada, ShinNarayan, Ramesh2016-06-062010Steiner, James F., Jeffrey E. McClintock, Ronald A. Remillard, Lijun Gou, Shin’ya Yamada, and Ramesh Narayan. 2010. The constant inner-disk radius of LMC X-3: A basis for measuring black hole spin. The Astrophysical Journal Letters 718, no. 2: L117–L121. doi:10.1088/2041-8205/718/2/l117.2041-8205http://nrs.harvard.edu/urn-3:HUL.InstRepos:27231582he black hole binary system LMC X-3 has been observed by virtually every X-ray mission since the inception of X-ray astronomy. Among the persistent sources, LMC X-3 is uniquely both habitually soft and highly variable. Using a fully relativistic accretion disk model, we analyze hundreds of spectra collected during eight X-ray missions that span 26 years. For a selected sample of 391 RXTE spectra, we find that to within ≈2% the inner radius of the accretion disk is constant over time and unaffected by source variability. Even considering an ensemble of eight X-ray missions, we find consistent values of the radius to within ≈4%–6%. Our results provide strong evidence for the existence of a fixed inner-disk radius. The only reasonable inference is that this radius is closely associated with the general relativistic innermost stable circular orbit. Our findings establish a firm foundation for the measurement of black hole spin.en-USaccretionaccretion disksblack hole physicsx-ray binarystarsLMC X-3Journal Article2016-04-0120102016-06-0610.1088/2041-8205/718/2/l117