Dynamics of tidal disruption events: statistical properties

Abstract

ABSTRACT We study the correlations between the dynamical history of a star that eventually experiences a tidal disruption event (TDE) and the properties of the TDE itself. As expected, we find that (i) in empty loss cone at the radius of influence, most TDEs are non-violent TDEs; i.e. the star’s periastron is only a bit smaller than the tidal radius. These stars had experienced strong tidal interactions with the supermassive black hole (SMBH), just slightly outside the tidal radius. (ii) In full loss cone at the radius of influence, most TDEs are violent; i.e. the star’s periastron is significantly smaller than the tidal radius. These stars did not previously encounter strong tidal effects. Nevertheless, we demonstrate that even in extremely empty or extremely full loss cone a finite fraction of order ${\sim} 10{{\ \rm per\ cent}}$ of the events are non-typical. This is due to two surprising effects: (i) In an empty loss cone, a logarithmic fraction of the events are associated with stars that entered the loss cone via strong scatterings. Those events are usually violent penetrating deep into the loss cone. (ii) In full loss cone, orbits with semimajor axis smaller than the radius of influence, where the loss cone is marginally empty, dominate the TDE rate. As a result, a constant fraction of TDEs involve stars in empty loss cone orbits, which have typically experienced strong interactions with the SMBH in previous orbits.