2006/06/14 by M. van den Berg, J. Grindlay, S. Laycock +10 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Scientific Research and Discoveries #astro-ph
paper · pdf · doi:10.1086/506613
published as Astrophys.J.647:L135-L138,2006 · 4 pages, 3 figures (1 color figure), accepted for publication in ApJ Letters
arxiv created 2006/06/14 · openalex publication_date 2006/08/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
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—that is, 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 in which 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 eight 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 ≲ Γ ≲ 1.5) suggests that our sample includes systems similar to the symbiotics recently detected with INTEGRAL and Swift .