Simulataneous X-ray and optical observations of LMC X-2

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 L_x ~ 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 (T_th~5keV) plasma and a cooler blackbody radiation (T_bb~1.3keV) or by a comptonized thermal (T_co~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.