A candidate for True Type-2 AGN without hidden central BLRs Identified by central Tidal Disruption Event

TL;DR

This study identifies SDSS J233454.07+145712.9 as a candidate True Type-2 AGN lacking hidden broad line regions, using TDE variability and spectroscopic analysis to distinguish it from typical AGN.

Contribution

It presents a novel method combining TDE signatures and spectroscopic data to identify True Type-2 AGN without hidden broad lines.

Findings

TDE analysis suggests a star disrupted by the central black hole within 20 light-days.

Optical spectra show only narrow emission lines, disfavoring broad line regions.

SDSS J2334 is a potential True Type-2 AGN confirmed by multiple lines of evidence.

Abstract

In this manuscript, through applications of TDE (tidal disruption event) expected variability properties, a potential candidate for True type-2 AGN without hidden central broad line regions (=TT2AGN) is reported in the SDSS J233454.07+145712.9 (=SDSS J2334). Through analyzing the 20-years optical light curves of SDSS J2334 from different Sky Survey projects, a TDE is preferred with a $4.7{\rm M_\odot}$ main-sequence star tidally disrupted by the central BH with mass $11.7\times 10^6{\rm M_\odot}$, indicating that central region within distance about 20 light-days to central BH in SDSS J2334 is directly in the line-of-sight. Moreover, AGN activities in SDSS J2334 can be confirmed through applications of BPT diagrams. Meanwhile, comparing virial BH mass determined through assumed broad Balmer emission components and M-sigma expected BH mass by well measured stellar velocity dispersion through stellar absorption features, optical broad emission lines in SDSS J2334 are disfavored with confidence level higher than 6$\sigma$. Therefore, combining the unique properties of the TDE and the spectroscopic results with only narrow emission lines, SDSS J2334 can be well identified as a potential candidate for a TT2AGN. The results indicate the to detect TDE expected flares in normal Type-2 AGN classified by spectroscopic results should be a new practicable method for identifying