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Detection of a Quiescent Low Mass X-Ray Binary Companion in 47 Tucanae

Peter D. Edmonds·Craig O. Heinke·Jonathan E. Grindlay·Ronald L. Gilliland
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Abstract

We present the results of a search for optical counterparts to the two quiescent low mass X-ray binaries (X5 and X7) in the globular cluster 47 Tucanae, using high quality Chandra and HST images. A faint blue (V=21.7; U-V=0.9) star within 0.03" of the eclipsing system X5 shows variability on both short and long timescales, and is the counterpart of the X-ray source. The colors and variability of this object are consistent with the combination of light from an accretion disk and a red main sequence star (possibly somewhat larger than a normal MS star with similar luminosity). No evidence is found for a star showing either variability or unusual colors near the position of X7, but a probable chance superposition of a star with V=20.25 limits the depth of our search.

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Peter D. Edmonds, Craig O. Heinke, Jonathan E. Grindlay, Ronald L. Gilliland. 2001-11-20. Detection of a Quiescent Low Mass X-Ray Binary Companion in 47 Tucanae. https://doi.org/10.1086/338776

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