APPLICATION OF A GENERAL RELATIVISTIC ACCRETION DISK MODEL TO LMC X-1, LMC X-3, X1608-522, AND X1636-536

We compare the persistent X-ray spectra of black hole candidates and X-ray bursters with a model spectrum of an accretion disk around either a black hole or a neutron star. The model takes account of general relativity and assumes that the accretion disk is geometrically thin and in a steady state. First we compare this general relativistic model with other conventional model spectra that have been used to fit observations so far. It is shown that the general relativistic model, in shape, is quite similar to the multicolor disk model and the Sunyaev-Titarchuk Comptonization model. Through the medium of these conventional models, we perform spectral fitting analysis on the black hole candidates LMC X-1 nad LMC X-3 and on the X-ray bursters X1608-522 and X1636-536 using the general relativistic model. As a result, we obtain the lower limit of the masses of LMC X-1 and LMC X-3 and the probable masses of X1608-522 and X1636-533. The former masses are larger than the theoretical upper limit of the neutron star mass, 2.5 M., and the latter masses are consistent with the canonical neutron star mass, 1.4 M..