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The former companion of hyper-velocity star S5-HVS1

Lu, Wenbin and Fuller, Jim and Raveh, Yael and Perets, Hagai B. and Li, Ting S. and Hosek, Matthew W., Jr. and Do, Tuan (2021) The former companion of hyper-velocity star S5-HVS1. Monthly Notices of the Royal Astronomical Society, 503 (1). pp. 603-613. ISSN 0035-8711. doi:10.1093/mnras/stab459.

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The hyper-velocity star S5-HVS1, ejected 5 Myr ago from the Galactic Centre at 1800 km s⁻¹, was most likely produced by tidal break-up of a tight binary by the supermassive black hole SgrA*. Taking a Monte Carlo approach, we show that the former companion of S5-HVS1 was likely a main-sequence star between 1.2 and 6 M⊙ and was captured into a highly eccentric orbit with pericentre distance in the range of 1–10 au and semimajor axis about 10³ au. We then explore the fate of the captured star. We find that the heat deposited by tidally excited stellar oscillation modes leads to runaway disruption if the pericentre distance is smaller than about 3au⁠. Over the past 5 Myr, its angular momentum has been significantly modified by orbital relaxation, which may stochastically drive the pericentre inwards below 3au and cause tidal disruption. We find an overall survival probability in the range 5 per cent to 50 per cent, depending on the local relaxation time in the close environment of the captured star, and the initial pericentre at capture. The pericentre distance of the surviving star has migrated to 10–100 au, making it potentially the most extreme member of the S-star cluster. From the ejection rate of S5-HVS1-like stars, we estimate that there may currently be a few stars in such highly eccentric orbits. They should be detectable (typically K_s ≲ 18.5 mag) by the GRAVITY instrument and by future Extremely Large Telescopes and hence provide an extraordinary probe of the spin of SgrA*.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lu, Wenbin0000-0002-1568-7461
Fuller, Jim0000-0002-4544-0750
Perets, Hagai B.0000-0002-5004-199X
Li, Ting S.0000-0002-9110-6163
Hosek, Matthew W., Jr.0000-0003-2874-1196
Do, Tuan0000-0001-9554-6062
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 February 11. Received 2021 January 18; in original form 2020 May 24. We thank Reinhard Genzel, Aleksey Generozov, Clément Bonnerot, Saul Teukolsky for useful discussions. WL was supported by the David and Ellen Lee Fellowship at Caltech. JF acknowledges support from an Innovator Grant from The Rose Hills Foundation, and the Sloan Foundation through grant FG2018-10515. HBP is grateful for the support from the Kingsley distinguished-visitor program at Caltech. TSL was supported by NASA through Hubble Fellowship grant HST-HF2-51439.001, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. MWH acknowledges support by NASA through grant HST-GO-15199.001-A. TD was supported by NSF AAG AST-1909554. Data Availability: The data underlying this article will be shared on reasonable request to the corresponding author.
Group:TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
David and Ellen Lee Postdoctoral ScholarshipUNSPECIFIED
Rose Hills FoundationUNSPECIFIED
Alfred P. Sloan FoundationFG2018-10515
Kingsley FellowshipUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51439.001
NASA Hubble FellowshipHST-GO-15199.001-A
Subject Keywords:black hole physics – stars: kinematics and dynamics – stars: oscillations – Galaxy: centre
Issue or Number:1
Record Number:CaltechAUTHORS:20200609-071005022
Persistent URL:
Official Citation:Wenbin Lu, Jim Fuller, Yael Raveh, Hagai B Perets, Ting S Li, Matthew W Hosek, Jr, Tuan Do, The former companion of hyper-velocity star S5-HVS1, Monthly Notices of the Royal Astronomical Society, Volume 503, Issue 1, May 2021, Pages 603–613,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103780
Deposited By: Tony Diaz
Deposited On:09 Jun 2020 18:06
Last Modified:16 Nov 2021 18:25

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