Further evidence of Quasiperiodic Eruptions in a tidal disruption event AT2019vcb by SRG/eROSITA

TL;DR

This paper presents evidence of quasiperiodic eruptions in a tidal disruption event AT2019vcb, observed through X-ray flares detected by SRG/eROSITA and XMM-Newton, linking TDEs with QPE phenomena.

Contribution

It provides the first detailed evidence of QPEs in AT2019vcb, strengthening the connection between TDEs and QPEs through multi-epoch X-ray observations.

Findings

X-ray flares lasted less than 12 hours with high amplitude.

Flares observed 7 months after TDE onset suggest quasiperiodic behavior.

Results support the TDE-QPE connection in astrophysical phenomena.

Abstract

We report the discovery of a short, large amplitude X-ray flare from AT2019vcb (aka Tormund), a tidal disruption event at $z=0.088$. The discovery is based on the data from the SRG/eROSITA X-ray telescope which happened to observe the source seven months after the onset of the optical TDE. eROSITA observation occurred 13 days after a soft flare was detected in the XMM-Newton data by Quintin et al. 2023. Both events bear similar characteristics in terms of timing and spectral properties. eROSITA spectrum is described as an accretion disk with a characteristic temperature of $\sim180$ eV and luminosity $\sim8\times10^{43}$ erg/s. The eROSITA flare lasted less than 12 hours and had an amplitude $\ge70$ with respect to the quiescent level, no flares were detected in later eROSITA observations (6-18 months later). The XMM-Newton and eROSITA flares provide strong evidence that the TDE AT2019vcb is a bona fide QPE source. Our work further strengthens the direct connection between TDEs and QPE following similar recent results in a TDE AT2019qiz by Nicholl et al. 2024.