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Tidal breakup of triple stars in the Galactic Centre

Fragione, Giacomo and Gualandris, Alessia (2018) Tidal breakup of triple stars in the Galactic Centre Monthly Notices of the Royal Astronomical Society, 475 (4). pp. 4986-4993.

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The last decade has seen the detection of fast moving stars in the Galactic halo, the so-called hypervelocity stars (HVSs). While the bulk of this population is likely the result of a close encounter between a stellar binary and the supermassive black hole (MBH) in the Galactic Centre (GC), other mechanims may contribute fast stars to the sample. Few observed HVSs show apparent ages which are shorter than the flight time from the GC, thereby making the binary disruption scenario unlikely. These stars may be the result of the breakup of a stellar triple in the GC which led to the ejection of a hypervelocity binary (HVB). If such binary evolves into a blue straggler star due to internal processes after ejection, a rejuvenation is possible that make the star appear younger once detected in the halo. A triple disruption may also be responsible for the presence of HVBs, of which one candidate has now been observed. We present a numerical study of triple disruptions by the MBH in the GC and find that the most likely outcomes are the production of single HVSs and single/binary stars bound to the MBH, while the production of HVBs has a probability ≲1% regardless of the initial parameters. Assuming a triple fraction of ≈10% results in an ejection rate of ≲1 Gyr−1, insufficient to explain the sample of HVSs with lifetimes shorter than their flight time. We conclude that alternative mechanisms are responsible for the origin of such objects and HVBs in general.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Fragione, Giacomo
Date : 18 January 2018
DOI : 10.1093/mnras/sty145
Copyright Disclaimer : © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Uncontrolled Keywords : Stars: kinematics and dynamics. Galaxy: centre. Galaxy: kinematics and dynamics. Galaxies: star clusters: general.
Related URLs :
Depositing User : Clive Harris
Date Deposited : 16 Jan 2018 14:40
Last Modified : 16 Jan 2019 19:07

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