ASCA Observations of GX 354-0 and KS 1731-260

Abstract

We report on ASCA observations of the low mass X-ray binaries GX 354-0 and KS 1731-260. The spectrum of GX 354-0 is best described as a power-law or a Comptonized spectrum with tau ~ 5 and kT ~ 8 keV and a residual at ~6.5 keV. The residual may be a disk reflection or a Compton broadened Gaussian line from the hot inner ADAF-like coronal region. The absorption column density to the source is 2.9e22 cm^-2. No soft thermal component was detected. The spectrum from KS 1731-260 is softer and it is best fit with a two component model with a column density of 1.1e22 cm^-2. The likely interpretation is emission from a Comptonizing cloud with an optical depth tau>12 and either a neutron star or a disk blackbody emission. We discuss the likely location of the Comptonizing cloud for both sources within the context of several proposed emission models.

Accepted for publication in the Astrophysical Journal

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• Hard X-ray Emission From Low Mass X-ray Binaries
• RXTE Studies of Long-Term X-ray Spectral Variations in 4U 1820-30
• Strong Field Gravity and X-Ray Observations of 4U1820-30
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