Tidal disruption of white dwarfs in a modified gravity theory with SPH

TL;DR

This paper investigates how a modified gravity theory affects the tidal disruption of white dwarfs by black holes, using numerical simulations to identify observable differences from general relativity.

Contribution

It introduces a numerical study of white dwarf tidal disruptions within Eddington inspired Born-Infeld gravity, highlighting observable effects of the modified gravity parameter.

Findings

Departure from general relativity could be observationally significant.

Tidal kick velocity and debris fallback rates are affected by the modified gravity parameter.

Qualitative differences exist between modified gravity effects and stellar rotation.

Abstract

Low energy imprints of modifications to general relativity are often found in pressure balance equations inside stars. These modifications are then amenable to tests via astrophysical phenomena, using observational effects in stellar astrophysics that crucially depend on such equations. One such effect is tidal disruption of stars in the vicinity of black holes. In this paper, using a numerical scheme modelled with smoothed particle hydrodynamics, we study real time tidal disruption of a class of white dwarfs by intermediate-mass black holes, in the low energy limit of a theory of modified gravity that alters the internal physics of white dwarfs, namely the Eddington inspired Born-Infeld theory. In this single parameter extension of general relativity, the mass-radius relation of white dwarfs as well as their tidal disruption radius depend on the modified gravity parameter, and these capture the effect of modifications to general relativity. Our numerical simulations incorporating these show that departure from general relativity in these scenarios might be observationally significant, and should therefore be contrasted with data. In particular, we study observationally relevant physical quantities, i.e., tidal kick velocity and trajectory deviation of the remnant core and fallback rates of the tidal debris in this theory and compare them to the Newtonian limit of general relativity. We also comment on the qualitative differences between the modified gravity theory and one with stellar rotation.