Gemini Spectroscopy of Galactic Bulge Sources: A Population of Hidden Accreting Binaries Revealed?

J. Wu, P. Jonker, M. Torres, Christopher Britt, C. Johnson, R.I. Hynes, S. Greiss, D. Steeghs, Thomas Maccarone, C.Õ. Heinke, T. Wevers

Research output: Contribution to conferencePaper

Abstract

We present Gemini spectroscopy for 21 X-ray sources detected in the Galactic Bulge Survey (GBS), which aims to investigate X-ray binaries in the Galactic Bulge region. For the majority of the sources, we have obtained spectra of the objects that are likely the real optical counterparts to the X-ray sources. Line measurements, spectral classification, and radial velocity analysis were performed on the Gemini spectra. We discover a population of hidden accreting binaries whose Gemini spectra apparently show neither strong H$α$ emission nor H$α$ absorption. However, the residual spectra of some sources after subtracting the best-fit stellar spectroscopic templates contain a broad H$α$ emission line which likely originates in an accretion disk. These hidden accreting sources may constitute a substantial portion of the full accreting binary population. We also identify three likely candidates of eclipsing or high-inclination quiescent low-mass X-ray binaries based on their broad H$α$ emiss
Original languageEnglish
StatePublished - Jan 2015

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