Formation of black hole x-ray binaries in globular clusters

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Issue Date
2010-07-10
Authors
Ivanova, Natalia
Chaichenets, Semyon
Fregeau, John
Heinke, Craig O.
Lombardi, James C., Jr. (Jamie)
Woods, Tyrone E.
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Keywords
galaxies: star clusters: general , stars: kinematics and dynamics , X-rays: binaries
Abstract
Inspired by the recent identification in extragalactic globular clusters of the first candidate black hole–white dwarf (BH–WD) X-ray binaries, where the compact accretors may be stellar-mass black holes (BHs), we explore how such binaries could be formed in a dynamical environment. We provide analyses of the formation rates via well-known formation channels like binary exchange and physical collisions and propose that the only possibility of forming BH–WD binaries is via coupling these usual formation channels with subsequent hardening and/or triple formation. In particular, we find that the most important mechanism for the creation of a BH–WD X-ray binary from an initially dynamically formed BH–WD binary is mass transfer induced in a triple system via the Kozai mechanism. Furthermore, we find that BH–WD binaries that evolve into X-ray sources can be formed by exchanges of a BH into a WD–WD binary or possibly by collisions of a BH and a giant star. If BHs undergo significant evaporation from the cluster or form a completely detached subcluster of BHs, then we cannot match the observationally inferred production rates even using the most optimistic estimates of formation rates. To explain the observations with stellar-mass BH–WD binaries, at least 1% of all formed BHs, or presumably 10% of the BHs present in the core now, must be involved in interactions with the rest of the core stellar population.
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Physics
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This article has been accepted for publication in The Astrophysical Journal ©: 2010. Ivanova, N., Chaichenets, S., Fregeau, J., Heinke, C.O., Lombardi, J.C. Jr, and Woods, T.E. Published by the American Astronomical Society. All rights reserved.
Citation
Ivanova, N., Chaichenets, S., Fregeau, J., Heinke, C.O., Lombardi, J.C. Jr., and Woods, T.E. (2010). Formation of black hole x-ray binaries in globular clusters. The Astrophysical Journal 717(2): 948-957. doi: 10.1088/0004-637X/717/2/948
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Institute of Physics
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