Tidal breakup of quadruple stars in the Galactic Centre

Giacomo Fragione*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

The most likely origin of hypervelocity stars is the tidal disruption of a binary star by the supermassive black hole (MBH) in the Galactic Centre (GC). However, HE0437-5439, a 9M B-type main-sequence star moving with a heliocentric radial velocity of about 720 km s-1 at a distance of ~60 kpc, and the recent discovered hypervelocity binary candidate (HVB), travelling at ~570 km s-1, challenge this standard scenario. Recently, Fragione & Gualandris have demonstrated that the tidal breakup of a triple star leads to an insufficient rate. Observations show that quadruple stars made up of two binaries orbiting their common centre of mass (the so-called 2+2 quadruples) are ≈ 4 per cent of the stars in the solar neighbourhood. Although rarer than triples, 2+2 quadruple stars may have a role in ejecting HVBs as due to their larger energy reservoir. We present a numerical study of 2+2 quadruple disruptions by the MBH in the GC and find that the production of HVBs has a probability ≲ 2-4 per cent, which translates into an ejection rate of ≲ 1Gyr-1, comparable to the triple disruption scenario. Given the low-ejection rate, we suggest that alternative mechanisms are responsible for the origin of HVBs, as the ejection from the interaction of a young star cluster with the MBH in the GC and the origin in the Large Magellanic Cloud.

Original languageEnglish (US)
Pages (from-to)2615-2622
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume479
Issue number2
DOIs
StatePublished - Sep 11 2018
Externally publishedYes

Keywords

  • Galaxies: star clusters: general
  • Galaxy: centre -Galaxy: kinematics and dynamics
  • Stars: kinematics and dynamics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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