ChaMPlane Discovery of Candidate Symbiotic Binaries in Baade's and   Stanek's Windows
  We have searched the OGLE-II archive for candidate counterparts of X-ray sources detected in two low-extinction windows included in our Galactic bulge Chandra/HST survey. We find that a significant number - i.e. in excess of the expected level of random associations - can be matched with probable M-giants. Their X-ray properties can be understood if these sources are symbiotic binaries where the X-rays are typically, either directly or indirectly, the result of a white dwarf accreting from the wind of a cool giant. Optical and near-infrared properties of selected sources are consistent with a symbiotic nature, although none of the spectra collected for 8 out of 13 candidate counterparts show the high-ionization nebular emission lines observed for many symbiotics. The hard X-ray emission for several sources (power-law photon indices -1.5 ~< Gamma ~< 1.5) suggests our sample includes systems similar to the symbiotics recently detected with INTEGRAL and Swift. 
M. van den Berg (1), J. Grindlay (1), S. Laycock (1), J. Hong (1), P.   Zhao (1), X. Koenig (1), E. M. Schlegel (2), H. Cohn...