X-Ray Spectrum and Variability of the Black Hole Candidate LMC X-3
Maraschi, L.; Tanzi, E. G.; Chiappetti, L.; Stella, L.; Belloni, T.; van der Klis, M.; Treves, A.
Italy, Netherlands
Abstract
LMC X-3 was observed on seven occasions in 1983-1984 with the EXOSAT satellite covering various orbital phases. No phase related variability was detected, while the X-ray flux increased gradually by ~ 30% in two weeks. Analysis of the short term variability in terms of autocorrelation reveals a minimum time scale of 600 s, with an rms amplitude of ~ 1%. Energy spectra in the 0.3-9 keV range have been fitted with various analytical laws. A good fit is obtained with the Comptonization spectrum given by Sunyaev and Titarchuk, yielding an optical depth τ ~ 23 and a temperature of ~ 1 keV. The results are compared with those of Cygnus X-1 in the low state and with the expectations of the standard accretion disk model.