ar X iv : a st ro - p h / 03 07 04 5 v 1 2 J ul 2 00 3 Chandra Observations of the Faintest Low - Mass X - ray Binaries

There exists a group of persistently faint galactic X-ray sources that, based on their location in the galaxy, high Lx/Lopt, association with X-ray bursts, and absence of low frequency Xray pulsations, are thought to be low-mass X-ray binaries (LMXBs). We present results from Chandra observations for eight of these systems: 4U 1708–408, 2S 1711–339, KS 1739–304, SLX 1735–269, GRS 1736–297, SLX 1746–331, 1E 1746.7–3224, and 4U 1812–12. Locations for all sources, excluding GRS 1736–297, SLX 1746–331, and KS 1739–304 (which were not detected) were improved to 0.6 error circles (90% confidence). Our observations support earlier findings of transient behavior of GRS 1736-297, KS 1739–304, SLX 1746-331, and 2S 1711-339 (which we detect in one of two observations). Energy spectra for 4U 1708–408, 2S 1711–339, SLX 1735–269, 1E 1746.7-3224, and 4U 1812–12 are hard, with power law indices typically 1.4-2.1, which are consistent with typical faint LMXB spectra. Subject headings: Accretion, Accretion Disks, Stars: Binaries: Close, stars: individual (4U 1708–408, 2S 1711–339, KS 1739–304, SLX 1735–269, GRS 1736–297, SLX 1746–331, 1E 1746.7–3224, 4U 1812–12),