Energy spectra of low-mass binary X-ray sources observed from Tenma.

Observations of X-ray spectra for four low-mass binary X-ray sources, Sco X-1, 4U 1608-522, GX5-1 and GX349+2 were performed with the gas scintillation proportional counters on board Tenma. Common to the four sources, the spectrum hardens with increasing intensity, and the difference of the spectra before and after an intensity increase shows invariably a blackbody spectrum of kT ≅ 2 keV. Every observed spectrum can be expressed by a sum of two spectral components: a hard component and a soft component, whose spectral shapes are fixed for each individual source.