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Dynamics and Interactions of Binaries and Neutron Stars in Globular Clusters

Sigurdsson, Steinn and Phinney, E. S. (1995) Dynamics and Interactions of Binaries and Neutron Stars in Globular Clusters. Astrophysical Journal Supplement Series, 99 . pp. 609-635. ISSN 0067-0049. doi:10.1086/192199.

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We model the dynamics of test binaries in isotropic, multimass models of Galactic globular clusters. The evolution of binary orbits through the cluster potentials is modeled, including second-order diffusion terms, and probabilities for close encounters with field stars are calculated. We carry out Monte Carlo simulations of the effects of the binary-single star encounters on the binary population and distribution in the cluster, and estimate the collision rate for different stellar populations in globular clusters with different structural parameters. In particular, we consider the rate for neutron stars and massive white dwarfs to undergo mass transfer due to collisional encounters, and hence estimate the population of observable millisecond pulsars in different clusters formed by binary-single star encounters. Assuming a Salpeter IMF, for low concentration clusters the core encounter rate is dominated by turnoff mass main-sequence stars and medium mass white dwarfs. For high concentration, high- density clusters the encounter probabilities are increasingly dominated by neutron stars and heavy white dwarfs. Hence we predict a smaller ratio of blue stragglers and cataclysmic variables to pulsars in high concentration clusters. The total number of millisecond pulsars, and the ratio of single to binary pulsars, is broadly consistent with the observed population, suggesting the binary-single star encounters contribute significantly to the pulsar formation rate in globular clusters, for the whole range of globular cluster types. The number of millisecond pulsars and the ratio of pulsars in different globular clusters is best explained by a total binary fraction comparable to that of the Galaxy, and a modest number of primordial neutron stars in the globular clusters.

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Additional Information:© 1995. The American Astronomical Society. Received 1994 September 15; accepted 1994 December 30. We would like to thank D. Chemoff for helpful discussion and comments. This research was supported in part by NASA grants NAGW-2144 and NAGW-2422, the NSF under grants AST 90-18526 and ASC 93-18185, and an ASF Thor Thors fellowship.
Funding AgencyGrant Number
NSFAST 90-18526
NSFASC 93-18185
American-Scandinavian FoundationUNSPECIFIED
Subject Keywords:binaries: general —celestial mechanics, stellar dynamics—globular clusters: general—methods: numerical—pulsars: general—stars: neutron
Record Number:CaltechAUTHORS:20190205-142100646
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92693
Deposited By: George Porter
Deposited On:05 Feb 2019 23:27
Last Modified:16 Nov 2021 03:52

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