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Ejection and Capture Dynamics in Restricted Three-body Encounters

Kobayashi, Shiho and Hainick, Yanir and Sari, Re'em and Rossi, Elena M. (2012) Ejection and Capture Dynamics in Restricted Three-body Encounters. Astrophysical Journal, 748 (2). p. 105. ISSN 0004-637X. doi:10.1088/0004-637X/748/2/105.

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We study the tidal disruption of binaries by a massive point mass (e.g., the black hole at the Galactic center), and we discuss how the ejection and capture preference between unequal-mass binary members depends on which orbit they approach the massive object. We show that the restricted three-body approximation provides a simple and clear description of the dynamics. The orbit of a binary with mass m around a massive object M should be almost parabolic with an eccentricity of |1 – e| ≲ (m/M)^(1/3) ≪ 1 for a member to be captured, while the other is ejected. Indeed, the energy change of the members obtained for a parabolic orbit can be used to describe non-parabolic cases. If a binary has an encounter velocity much larger than (M/m)^(1/3) times the binary rotation velocity, it would be abruptly disrupted, and the energy change at the encounter can be evaluated in a simple disruption model. We evaluate the probability distributions for the ejection and capture of circular binary members and for the final energies. In principle, for any hyperbolic (elliptic) orbit, the heavier member has more chance to be ejected (captured), because it carries a larger fraction of the orbital energy. However, if the orbital energy is close to zero, the difference between the two members becomes small, and there is practically no ejection and capture preferences. The preference becomes significant when the orbital energy is comparable to the typical energy change at the encounter. We discuss its implications to hypervelocity stars and irregular satellites around giant planets.

Item Type:Article
Related URLs:
URLURL TypeDescription
Sari, Re'em0000-0002-1084-3656
Additional Information:© 2012 American Astronomical Society. Received 2011 November 22; accepted 2012 January 20; published 2012 March 13. We thank the referee, Hagai Perets, for his constructive comments, and Mostafa Ahmadi, Phil Armitage, Witold Maciejewski, and Ruth Murray Clay for useful discussion. This research was supported by STFC, ERC, and IRG grants, and Packard, Guggenheim, and Radcliffe fellowships.
Funding AgencyGrant Number
Packard FellowshipUNSPECIFIED
Guggenheim FellowshipUNSPECIFIED
Radcliffe FellowshipUNSPECIFIED
Subject Keywords:binaries: general; Galaxy: center; Galaxy: halo; Galaxy: kinematics and dynamics; planets and satellites: formation; planets and satellites: individual (Triton)
Issue or Number:2
Record Number:CaltechAUTHORS:20120504-154505289
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Official Citation:Ejection and Capture Dynamics in Restricted Three-body Encounters Shiho Kobayashi et al. 2012 ApJ 748 105
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31316
Deposited By: Jason Perez
Deposited On:07 May 2012 20:16
Last Modified:09 Nov 2021 19:50

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