TY - JOUR

T1 - Stars Crushed by Black Holes. III. Mild Compression of Radiative Stars by Supermassive Black Holes

AU - Kundu, Suman Kumar

AU - Coughlin, Eric R.

AU - Nixon, C. J.

N1 - Funding Information:
To analyze the amount of tidal compression of a radiative, solar-like star (modeled with the Eddington standard model) during a TDE, we used an analytic model originally proposed by Coughlin & Nixon () that accounts for both the self-gravity and the pressure of the star during its tidal encounter with the black hole (Section ). We then relaxed the assumptions made within that model by performing three-dimensional simulations of deep TDEs that satisfied 2 ≤ β ≤ 10, where β = r / r with r the stellar pericenter distance and r the canonical tidal radius, verified the numerical accuracy of our results by varying the spatial resolution, and performed additional simulations in the Schwarzschild metric to assess the importance of general relativity (Section ). We showed that the two methods—analytical and numerical—agree very well in their predictions for the maximum density and temperature reached during the disruption, and we therefore conclude that We thank the referee for useful and constructive comments. S.K.K. and E.R.C. acknowledge support from the National Science Foundation through grant AST-2006684, and E.R.C. acknowledges additional support from the Oakridge Associated Universities through a Ralph E. Powe Junior Faculty Enhancement Award. C.J.N. acknowledges support from the Science and Technology Facilities Council [grant number ST/W000857/1]. Some of this work was carried out using the Syracuse University HTC Campus Grid and the NSF award ACI-1341006. We used SPLASH (Price ) for Figure . t p p t
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.

PY - 2022/11/1

Y1 - 2022/11/1

N2 - A tidal disruption event (TDE) occurs when the gravitational field of a supermassive black hole (SMBH) destroys a star. For TDEs in which the star enters deep within the tidal radius, such that the ratio of the tidal radius to the pericenter distance β satisfies β ≫ 1, the star is tidally compressed and heated. It was predicted that the maximum density and temperature attained during deep TDEs scale as ∝ β 3 and ∝ β 2, respectively, and nuclear detonation is triggered by β ≳ 5, but these predictions have been debated over the last four decades. We perform Newtonian smoothed-particle hydrodynamics simulations of deep TDEs between a Sun-like star and a 106 M ⊙ SMBH for 2 ≤ β ≤ 10. We find that neither the maximum density nor temperature follow the ∝ β 3 and ∝ β 2 scalings or, for that matter, any power-law dependence, and that the maximum-achieved density and temperature are reduced by ∼1 order of magnitude compared to past predictions. We also perform simulations in the Schwarzschild metric and find that relativistic effects modestly increase the maximum density (by a factor of ≲1.5) and induce a time lag relative to the Newtonian simulations, which is induced by time dilation. We also confirm that the time the star spends at high density and temperature is a very small fraction of its dynamical time. We therefore predict that the amount of nuclear burning achieved by radiative stars during deep TDEs is minimal.

AB - A tidal disruption event (TDE) occurs when the gravitational field of a supermassive black hole (SMBH) destroys a star. For TDEs in which the star enters deep within the tidal radius, such that the ratio of the tidal radius to the pericenter distance β satisfies β ≫ 1, the star is tidally compressed and heated. It was predicted that the maximum density and temperature attained during deep TDEs scale as ∝ β 3 and ∝ β 2, respectively, and nuclear detonation is triggered by β ≳ 5, but these predictions have been debated over the last four decades. We perform Newtonian smoothed-particle hydrodynamics simulations of deep TDEs between a Sun-like star and a 106 M ⊙ SMBH for 2 ≤ β ≤ 10. We find that neither the maximum density nor temperature follow the ∝ β 3 and ∝ β 2 scalings or, for that matter, any power-law dependence, and that the maximum-achieved density and temperature are reduced by ∼1 order of magnitude compared to past predictions. We also perform simulations in the Schwarzschild metric and find that relativistic effects modestly increase the maximum density (by a factor of ≲1.5) and induce a time lag relative to the Newtonian simulations, which is induced by time dilation. We also confirm that the time the star spends at high density and temperature is a very small fraction of its dynamical time. We therefore predict that the amount of nuclear burning achieved by radiative stars during deep TDEs is minimal.

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U2 - 10.3847/1538-4357/ac9734

DO - 10.3847/1538-4357/ac9734

M3 - Article

AN - SCOPUS:85142052020

SN - 0004-637X

VL - 939

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 71

ER -