Tidal Disruptions of Mainsequence Stars. IV. Relativistic Effects and Dependence on Black Hole Mass
Abstract
Using a suite of fully relativistic hydrodynamic simulations applied to mainsequence stars with realistic internal density profiles, we examine full and partial tidal disruptions across a wide range of black hole mass ( ${10}^{5}\leqslant {M}_{\mathrm{BH}}/{M}_{\odot }\leqslant 5\times {10}^{7}$ ) and stellar mass ( $0.3\leqslant {M}_{\star }/{M}_{\odot }\leqslant 3$ ) as larger M_{BH} leads to stronger relativistic effects. For fixed M_{⋆}, as M_{BH} increases, the ratio of the maximum pericenter distance yielding full disruptions ( ${{ \mathcal R }}_{{\rm{t}}}$ ) to its Newtonian prediction rises rapidly, becoming triple the Newtonian value for ${M}_{\mathrm{BH}}=5\times {10}^{7}\,{M}_{\odot }$ , while the ratio of the energy width of the stellar debris for full disruptions to the Newtonian prediction decreases steeply, resulting in a factor of 2 correction at ${M}_{\mathrm{BH}}=5\times {10}^{7}\,{M}_{\odot }$ . We provide approximate formulae that express the relativistic corrections of both ${{ \mathcal R }}_{{\rm{t}}}$ and the energy width relative to their Newtonian approximate estimates. For partial disruptions, we find that the fractional remnant mass for a given ratio of the pericenter to ${{ \mathcal R }}_{{\rm{t}}}$ is higher for larger M_{BH}. These results have several implications. As M_{BH} increases above $\sim {10}^{7}\,{M}_{\odot }$ , the cross section for complete disruptions is suppressed by competition with direct capture. However, the crosssection ratio for partial to complete disruptions depends only weakly on M_{BH}. The relativistic correction to the debris energy width delays the time of peak massreturn rate and diminishes the magnitude of the peak return rate. For ${M}_{\mathrm{BH}}\gtrsim {10}^{7}\,{M}_{\odot }$ , the M_{BH}dependence of the full disruption cross section and the peak massreturn rate and time is influenced more by relativistic effects than by Newtonian dynamics.
 Publication:

The Astrophysical Journal
 Pub Date:
 December 2020
 DOI:
 10.3847/15384357/abb3cc
 arXiv:
 arXiv:2001.03504
 Bibcode:
 2020ApJ...904..101R
 Keywords:

 Black holes;
 Galactic center;
 Tidal disruption;
 General relativity;
 Supermassive black holes;
 Gravitation;
 162;
 565;
 1696;
 641;
 1663;
 661;
 Astrophysics  High Energy Astrophysical Phenomena;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 13 pages, 9 figures, 2 tables, accepted for publication in ApJ