Asca Observations of Gx 354-0 and Ks 1731-260

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 τ ∼ 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 2.9 × 10 22 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 1.1 × 10 22 cm −2. The likely interpretation is emission from a Comptonizing cloud with an optical depth τ > 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.