Tidal disruption and ignition of white dwarfs by moderately massive black holes

TL;DR

This paper uses numerical simulations to study how white dwarfs are tidally disrupted and ignited by moderately massive black holes, potentially producing observable X-ray flares and supernova-like explosions.

Contribution

It provides a realistic modeling of gas dynamics and nuclear reactions during white dwarf disruption by black holes, highlighting possible explosive outcomes and observational signatures.

Findings

Nuclear energy release can be comparable to type Ia supernovae.

Disruption leads to bright X-ray flares lasting about a year.

A significant fraction of debris remains bound to the black hole.

Abstract

We present a numerical investigation of the tidal disruption of white dwarfs by moderately massive black holes, with particular reference to the centers of dwarf galaxies and globular clusters. Special attention is given to the fate of white dwarfs of all masses that approach the black hole close enough to be disrupted and severely compressed to such extent that explosive nuclear burning can be triggered. Consistent modeling of the gas dynamics together with the nuclear reactions allows for a realistic determination of the explosive energy release. In the most favorable cases, the nuclear energy release may be comparable to that of typical type Ia supernovae. Although the explosion will increase the mass fraction escaping on hyperbolic orbits, a good fraction of the debris remains to be swallowed by the hole, causing a bright soft X-ray flare lasting for about a year. Such transient signatures, if detected, would be a compelling testimony for the presence of a moderately mass black hole (below $10^5 M_\odot$).