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The former companion of the 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 (2020) The former companion of the hyper-velocity star S5-HVS1. . (Unpublished)

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The hyper-velocity star S5-HVS1, ejected 5 Myr ago from the Galactic Center at 1800 km/s, 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 1.5 and 6M⊙ and was captured into a highly eccentric orbit with pericenter distance in the range 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 pericenter distance is smaller than about 3 AU. Over the past 5 Myr, its angular momentum has been significantly modified by orbital relaxation, which may stochastically drive the pericenter inwards below 3 AU and cause tidal disruption. We find an overall survival probability in the range 5% to 50%, depending on the local relaxation time in the close environment of the captured star, and the initial pericenter at capture. The pericenter 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:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Lu, Wenbin0000-0002-1568-7461
Fuller, Jim0000-0002-4544-0750
Perets, Hagai B.0000-0002-5004-199X
Hosek, Matthew W., Jr.0000-0003-2874-1196
Do, Tuan0000-0001-9554-6062
Additional Information:We thank Reinhard Genzel, Aleksey Generozov, Clément Bonnerot, Saul Teukolsky for useful discussions. WL is supported by the David and Ellen Lee Fellowship at Caltech. HBP is greatful for the support from the Kingsley distinguished-visitor program at Caltech.
Group:TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
David and Ellen Lee Postdoctoral ScholarshipUNSPECIFIED
Kingsley FellowshipUNSPECIFIED
Subject Keywords:Galactic Center - hyper-velocity stars - stellar oscillations - tidal disruption events
Record Number:CaltechAUTHORS:20200609-071005022
Persistent URL:
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:09 Jun 2020 18:06

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