Abstract We study close encounters of a 1 M ⊙ middleage mainsequence star (modeled using MESA) with massive black holes through hydrodynamic simulations, and explore in particular the dependence of the outcomes on the black hole mass. We consider here black holes in the intermediatemass range, M BH = 100–10 4 M ⊙ . Possible outcomes vary from a small tidal perturbation for weak encounters all the way to partial or full disruption for stronger encounters. We find that stronger encounters lead to increased mass loss at the first pericenter passage, in many cases ejecting the partially disrupted star on an unbound orbit. For encounters that initially produce a bound system, with only partial stripping of the star, the fraction of mass stripped from the star increases with each subsequent pericenter passage and a stellar remnant of finite mass is ultimately ejected in all cases. The critical penetration depth that separates bound and unbound remnants has a dependence on the black hole mass when M BH ≲ 10 3 M ⊙ . We also find that the number of successive close passages before ejection decreases as we go from the stellarmass black hole to the intermediatemass black hole regime. For instance, after an initial encounter right at the classical tidal disruption limit, a 1 M ⊙ star undergoes 16 (5) pericenter passages before ejection from a 10 M ⊙ (100 M ⊙ ) black hole. Observations of periodic flares from these repeated close passages could in principle indicate signatures of a partial tidal disruption event.
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Hydrodynamics of Collisions and Close Encounters between Stellar Black Holes and Mainsequence Stars
Abstract Recent analyses have shown that close encounters between stars and stellar black holes occur frequently in dense star clusters. Depending upon the distance at closest approach, these interactions can lead to dissipating encounters such as tidal captures and disruptions, or direct physical collisions, all of which may be accompanied by bright electromagnetic transients. In this study, we perform a wide range of hydrodynamic simulations of close encounters between black holes and mainsequence stars that collectively cover the parameter space of interest, and we identify and classify the various possible outcomes. In the case of nearly headon collisions, the star is completely disrupted with roughly half of the stellar material becoming bound to the black hole. For more distant encounters near the classical tidaldisruption radius, the star is only partially disrupted on the first pericenter passage. Depending upon the interaction details, the partially disrupted stellar remnant may be tidally captured by the black hole or become unbound (in some cases, receiving a sufficiently large impulsive kick from asymmetric mass loss to be ejected from its host cluster). In the former case, the star will undergo additional pericenter passages before ultimately being disrupted fully. Based on the properties of the material bound to the black hole at the end of our simulations (in particular, the total bound mass and angular momentum), we comment upon the expected accretion process and associated electromagnetic signatures that are likely to result.
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 NSFPAR ID:
 10359302
 Date Published:
 Journal Name:
 The Astrophysical Journal
 Volume:
 933
 Issue:
 2
 ISSN:
 0004637X
 Page Range / eLocation ID:
 203
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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