Swift J1644+57: A White Dwarf Tidally Disrupted by a 10^4 M_{odot} Black Hole?

TL;DR

This paper suggests that Swift J1644+57 is a white dwarf tidally disrupted by an intermediate mass black hole, explaining its rapid flares and light curve features.

Contribution

It introduces a novel model where a white dwarf disruption accounts for the observed phenomena, differing from previous main sequence star disruption models.

Findings

White dwarf disruption explains short flare rise times (~100 s).

Flares' recurrence period (~5×10^4 s) matches white dwarf orbital passages.

Black hole mass estimated to be less than 10^5 solar masses.

Abstract

We propose that the remarkable object Swift J1644+57, in which multiple recurring hard X-ray flares were seen over a span of several days, is a system in which a white dwarf was tidally disrupted by an intermediate mass black hole. Disruption of a white dwarf rather than a main sequence star offers a number of advantages in understanding the multiple, and short, timescales seen in the light curve of this system. In particular, the short internal dynamical timescale of a white dwarf offers a more natural way of understanding the short rise times ($\sim 100$ s) observed. The relatively long intervals between flares ($\sim 5 \times 10^4$ s) may also be readily understood as the period between successive pericenter passages of the remnant white dwarf. In addition, the expected jet power is larger when a white dwarf is disrupted. If this model is correct, the black hole responsible must have mass $\lesssim 10^5 M_{\odot}$.