A central tidal disruption event candidate in high redshift quasar SDSS J000118.70+003314.0

TL;DR

This paper reports the identification of a high-redshift quasar TDE candidate, demonstrating that tidal disruption events can occur in active galactic nuclei and can be distinguished from intrinsic quasar variability.

Contribution

It presents the first candidate TDE in a high-redshift quasar with detailed analysis, expanding the understanding of TDE occurrence in active galaxies.

Findings

TDE candidate in a $z=1.404$ quasar with nine-year light curve variability.

Estimated disrupted star mass of approximately 1.9 solar masses.

Black hole mass inferred from TDE is significantly smaller than virial estimates.

Abstract

We report a high-redshift ($z=1.404$) tidal disruption event (TDE) candidate in SDSS J000118.70+003314.0 (SDSS J0001), which is a quasar with apparent broad Mg~{\sc ii} emission line. The long-term variability in its nine-year photometric $ugriz$-band light curves, obtained from the SDSS Stripe82 and the PHOTOOBJALL databases, can be described by the conventional TDE model. Our results suggest that the TDE is a main-sequence star with mass of $1.905_{-0.009}^{+0.023}{\rm M_\odot}$ tidally disrupted by a black hole (BH) with mass {$6.5_{-2.6}^{+3.5}\times10^7{\rm M_\odot}$}. The BH mass is about 7.5 times smaller than the virial BH mass derived from the broad Mg~{\sc ii} emission line, which can be explained by non-virial dynamic properties of broad emission lines from TDEs debris. Furthermore, we examine the probability that the event results from intrinsic variability of quasars, which is about $0.009\%$, through applications of the DRW/CAR process. Alternative explanations for the event are also discussed, such as the scenarios of dust obscurations, microlensing and accretion. Our results provide clues to support that TDEs could be detectable in broad line quasars as well as in quiescent galaxies, and to indicate the variability of some active galactic nuclei may be partly attributed to central TDEs.