Simultaneous X-Ray, Ultraviolet, and Optical Observations of LMC X-3
Maraschi, L.; Tanzi, E. G.; Belloni, T.; Falomo, R.; Treves, A.; Corbet, R. H. D.; Makishima, K.; Makino, F.; Ebisawa, K.; Miyamoto, S.
Italy, Germany, Japan
Abstract
The black hole candidate LMC X-3 was observed simultaneously at X- ray (Ginga), UV (IUE), and optical frequencies in 1988 January. The X- ray energy distribution is the superposition of a thermal component and a hard tail. The former component can be described equally well by a Comptonization spectrum or by a disk blackbody. In the latter picture, the high-energy tail may derive from the inner part of the accretion disk, which is hot and transparent. Optical and UV data indicate a very low state of the source. Comparing with 1984 observations, one finds that the optical-to-X-ray flux ratio is not maintained, possibly indicating a secular variation of the disk structure, or a change of the anisotropy of the X-ray emission.