Two Rapidly Variable Galactic X-ray Transients Observed with Chandra, XMM and Suzaku

C. O. Heinke(1), J. A. Tomsick(2), F. Yusef-Zadeh(3), J. E. Grindlay(4)


(1) University of Alberta, Dept. of Physics, 11322-89 Avenue, Edmonton AB, T6G 2G7, Canada
(2) Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450, USA
(3) Northwestern University, Dept. of Physics & Astronomy, 2145 Sheridan Rd., Evanston, IL 60208, USA
(4) Harvard University, Dept. of Astronomy, 60 Garden Street, Cambridge, MA 02138, USA

Paper: ApJ, August 2009, in press

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 NH variability, and hard spectra. XMMU J174445.5-295044 is seen at 2-10 keV fluxes of 3*10-11 to <10-12 ergs cm-2 s-1, with NH at or above 5*1022 cm-2, by XMM, Chandra, and Suzaku. A likely 2MASS counterpart with KS=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 FX(2-10 keV) 10-12 ergs cm-2 s-1, with large NH variations (from 2*1022 to >2*1023 cm-2). No 2MASS counterpart is visible, to KS>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.

Preprints available from the authors at cheinke@phys.ualberta.ca , or the raw TeX (no figures) if you click here.

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