Shock Breakouts from Tidal Disruption Events

TL;DR

This paper investigates the shock breakout radiation from tidal disruption events, highlighting its detectability in UV/optical wavelengths and estimating detection rates for surveys like LSST.

Contribution

It provides the first detailed analysis of shock breakout signals from tidal disruption events across different star types and predicts detection rates for upcoming surveys.

Findings

Shock breakout from main sequence stars emits X-ray radiation, but detection is challenging.

Red giant shock breakouts emit UV/visible light, making them easier to detect.

LSST could detect tidal disruption events once per month under certain galactic conditions.

Abstract

Tidal disruption events of stars by supermassive black holes have so far been discovered months to years after the fact. In this paper we explore the short, faint and hard burst of radiation is emitted at maximum compression, as a result of shock breakout. The detection of this burst can be used to capture tidal disruption events in real time. We verify that shock breakout from main sequence stars produces radiation in the X-ray range, but find that it is difficult to detect using all sky X-ray surveying telescopes. In the case of shock breakout from red giants, most of the radiation is emitted in the UV and visible range, which is significantly easier to detect. A similar burst of UV/optical radiation will also be emitted by stars puffed by tidal heating from a previous passage close to the central black hole. This radiation can be detected by surveys like ZTF and LSST. We calculate detection rates for different types of galactic nuclei. For the case of a very full loss cone we predict a detection rate of once per month with LSST, whereas for the case of a very empty loss cone we predict a rate of once per year with LSST. Evidence from a recent tidal disruption event, ASASSN-14li, seems to favour a very full loss cone, in which case LSST is expected to detect one such event every month.