Two Rapidly Variable Galactic X-ray Transients Observed with Chandra , Xmm-newton , And Suzaku

Abstract

We have identified two moderately bright, rapidly variable transients in new and archival X-ray data near the Galactic center. Both objects show strong, flaring variability on timescales of tens to thousands of seconds, evidence of N-H variability, and hard spectra. XMMU J174445.5-295044 is seen at 2-10 keV fluxes of 3 x 10(-11) to < 10(-12) erg cm(-2) s(-1), with N-H at or above 5 x 10(22) cm(-2), by XMM-Newton, Chandra, and Suzaku. A likely Two Micron All Sky Survey (2MASS) counterpart with K-S = 10.2 shows colors indicative of a late-type star. CXOU J174042.0-280724 is a likely counterpart to the fast hard transient IGR J17407-2808. Chandra observations find F-X(2-10 keV) similar to 10(-12) erg cm(-2) s(-1), with large N-H variations (from 2 x 10(22) to > 2 x 10(23) cm(-2)). No 2MASS counterpart is visible, to K-S > 13. XMMU J174445.5-295044 seems likely to be a new symbiotic star or symbiotic X-ray binary, while CXOU J174042.0-280724 is more mysterious, likely an unusual low-mass X-ray binary.