Simulataneous X-ray and optical observations of LMC X-2
Motch, C.; Beuermann, K.; Pakull, M.; van der Klis, M.; Bonnet-Bidaud, J. M.; Parmar, A.
France, Germany, Netherlands
Abstract
The X-ray source LMC X-2 was observed with EXOSAT for -8hours on February 2nd, 1984 with simultaneous photometric and spectroscopic optical coverage. The source was seen at a luminosity of Lx ~ 1.5 1038erg.s-1 with a mean X-ray spectrum which can be described equally well by either a superposition of a thermal emission of a thin hot (Tth~5keV) plasma and a cooler blackbody radiation (Tbb~1.3keV) or by a comptonized thermal (Tco~3keV) radiation. There is no evidence of iron line.
The mean source spectrum is found very alike those of the bright galactic bulge sources. The source is however only moderately variable in X-rays with spectral variations similar to those of Sco X-1 in quiescent state. No coherent periodic (0.016-2500s) pulsations are detected. Large photometric optical variations are present which suggest an orbital period of 6.4h though at a low level of significance. There is no clear correlation however between X-ray and optical variations.