The mass fallback rate of the debris in relativistic stellar tidal disruption events

Abstract

Highly energetic stellar tidal disruption events (TDEs) provide a way to study black hole characteristics and their environment. We simulate TDEs with the PHANTOM code in a general relativistic and Newtonian description of a supermassive black hole's gravity. Stars, which are placed on parabolic orbits with different parameters $\beta$, are constructed with the stellar evolution code MESA and therefore have realistic stellar density profiles. We study the mass fallback rate of the debris $\dot{M}$ and its dependence on the $\beta$, stellar mass and age as well as the black hole's spin and the choice of the gravity's description. We calculate peak value ${\dot{M}}_{\mathrm{peak}}$, time to the peak $t_{\mathrm{peak}}$, duration of the super-Eddington phase $t_{\mathrm{Edd}}$, time $t_{>0.5{\dot{M}}_{\mathrm{peak}}}$ during which $\dot{M}>0.5{\dot{M}}_{\mathrm{peak}}$, early rise-time ${\tau }_{\mathrm{rise}}$ and late-time slope $n_{\infty }$. We recover the trends of ${\dot{M}}_{\mathrm{peak}}$, $t_{\mathrm{peak}}$, ${\tau }_{\mathrm{rise}}$ and $n_{\infty }$ with $\beta$, stellar mass and age, which were obtained in previous studies. We find that $t_{\mathrm{Edd}}$, at a fixed $\beta$, scales primarily with the stellar mass, while $t_{>0.5{\dot{M}}_{\mathrm{peak}}}$ scales with the compactness of stars. The effect of SMBH's rotation depends on the orientation of its rotational axis relative to the direction of the stellar motion on the initial orbit. Encounters on prograde orbits result in narrower $\dot{M}$ curves with higher ${\dot{M}}_{\mathrm{peak}}$, while the opposite occurs for retrograde orbits. We find that disruptions, at the same pericenter distance, are stronger in a relativistic tidal field than in a Newtonian. Therefore, relativistic $\dot{M}$ curves have higher ${\dot{M}}_{\mathrm{peak}}$, and shorter $t_{\mathrm{peak}}$ and $t_{\mathrm{Edd}}$.

18 pages, 11 figures, accepted for publication in ApJ

References in corpus (4)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Stellar disruption by a supermassive black hole: is the light curve really proportional to $t^{-5/3}$?
• Tidal disruptions by rotating black holes: effects of spin and impact parameter
• Tidal disruption of a star in the Schwarzschild spacetime: relativistic effects in the return rate of debris

Cited by in corpus (4)

• Spin-induced offset stream self-crossing shocks in tidal disruption events
• The effect of relativistic precession on light curves of tidal disruption events
• Partial tidal disruption of White Dwarfs in off-equatorial orbits around Kerr black holes
• Evolution of Quasi-Periodic Eruptions in the post-TDE Accretion Disk Perturbed by an Orbiting Star