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
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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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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