Speaker
Description
The black hole candidate LMC X-1 is a persistently soft-state high-mass X-ray binary with an unusual luminosity--temperature relationship, and its inferred spin depends strongly on assumptions about disk structure and the treatment of the seed-photon spectrum. To investigate the role of Comptonization in shaping its thermal continuum, we analyze 10 Chandra High Energy Transmission Grating Spectrometer observations using eqpair as our primary spectral model. The model provides good fits to the broadband continuum after accounting for narrow absorption and emission features detected by the HETG, while also reproducing the unusual normalization--temperature trend. This suggests that scattering in a warm, optically thick layer may play an important role in this system. We further test this interpretation by fitting the spectra with a Comptonized disk model, thcomp $\times$ kerrbb, using a consistent set of physical parameters including black hole spin. These fits yield a moderate spin, $a^* \sim 0.5$, and a variable color-correction factor, $f_c \sim 1.7$--$2.0$, highlighting the extent to which inferred disk properties depend on the adopted treatment of Comptonization. Together, the eqpair and thcomp $\times$ kerrbb results suggest that LMC X-1's unusual thermal behavior may be better explained by changes in the disk atmosphere or corona rather than by large changes in the inner disk radius. As a cross-instrument check, we also apply these models to XMM-Newton observations of LMC X-1 to test whether the same Comptonization-based interpretation remains consistent across instruments.