Low-Mass X-Ray Binaries in the Large Magellanic Cloud

Abstract

We report results on three low-mass X-ray binaries (LMXB) in the LMC, obtained with EXOSAT, IUE and ground-based (ESO) telescopes: LMC X-2 which appears to be "Sco X-1"-like, LHG 83 and LHG 87. The latter are two weaker sources first detected in the course of the HEAO-B LMC survey. They have faint optical counterparts of which LHG 87 was only recently identified by us. In X-rays, they are characterized by ultrasoft X-ray spectra possibly characteristic of black-hole primaries. LHG 83 furthermore shows evidence for X-ray ionization of the surrounding interstellar medium, similar to the He III region around the black-hole candidate LMC X-1. X-ray binaries with masses of compact objects in excess of 3 M_⊙ and ultrasoft X-ray spectra are comparatively frequent in the LMC. We suggest that subcritical accretion onto black holes takes place in LHG 83 and LHG 87.