Kavli Affiliate: Pau Amaro Seoane
| First 5 Authors: Pau Amaro Seoane, , , ,
| Summary:
We have evidence of X-ray flares in several galaxies consistent with a a star
being tidally disrupted by a supermassive black hole (MBH). If the star starts
on a nearly parabolic orbit relative to the MBH, one can derive that the
fallback rate follows a $t^{-5/3}$ decay in the bolometric luminosity. We have
modified the standard version of the smoothed-particle hydrodynamics (SPH) code
{sc Gadget} to include a relativistic treatment of the gravitational forces.
We include non-spinning post-Newtonian corrections to incorpore the periapsis
shift and the spin-orbit coupling up to next-to-lowest order. We run a set of
simulations for different penetration factors in both the Newtonian- and the
relativistic regime. We find that tidal disruptions around MBHs in the
relativistic cases are underluminous for values starting at $beta gtrapprox
2.25$; i.e. the fallback curves produced in the relativistic cases are
progressively lower compared to the Newtonian simulations as the penetration
parameter increases. This is due to the fact that, contrary to the Newtonian
cases, we find that all relativistic counterparts feature a survival core for
penetration factors going to values as high as $12.05$. We derive a
relativistic calculation which shows that geodesics of the elements in the star
converge as compared to the Newtonian case, allowing for a core to survive the
tidal disruption. A survival core should consistently emerge from any TDE with
$beta gtrapprox 2.25$. The higher the value, the lower the colour
temperatures than derived from standard accretion models.
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