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

Gu Ying, Zheng Qi, Cheng Peizheng, Li Xiao, Xing-Qian Cheng, Zhang XueGuang, Liang EnWei

First listed 2025-05-27 | Last updated 2025-05-27

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$σ$. 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

Short digest

Reports SDSS J233454.07+145712.9 as a candidate true type‑2 AGN uncovered via a central TDE singled out in 20‑year optical light curves (CSS/PTF/PanSTARRS/ZTF), with a 2009–2013 outburst showing the steep‑rise/smooth‑decline template and otherwise quiescent behavior. TDE modeling (TDEFIT/MOSFIT) favors disruption of a 4.7 Msun main‑sequence star by a 1.17×10^7 Msun black hole, implying an unobscured line‑of‑sight to within ≈20 light‑days of the nucleus. Spectroscopy shows only narrow lines and BPT AGN classification; hypothetical broad Balmer components yield virial masses inconsistent with M–sigma at >6σ, disfavoring hidden BLRs. Together this positions SDSS J2334 as a TT2AGN candidate and demonstrates TDE flares as a practical route to identify BLR‑less nuclei among type‑2 spectra.

Key figures to inspect

• Figure 1: Inspect the multi‑survey light curves to see the 2009–2013 outburst and how the TDE template overlays each band; check the WISE W1/W2 panels for any mid‑IR echo relative to the dashed peak time and read off the MCMC posteriors that set the BH/star parameters.
• Figure 2: Examine the SSP spectral decomposition with and without an added AGN continuum to verify a narrow‑line–only spectrum and that host subtraction does not hide broad Balmer wings.
• Figure 3: Use the right‑hand M–sigma comparison to locate both the TDE‑inferred mass and the (rejected) virial mass from assumed broad lines relative to literature relations and the 3–6σ confidence bands.
• Figure 4: Compare fits around Hβ and Hα with models that include only narrow components (with blue‑shifted wings) versus versions forcing broad Balmer; residuals should reveal why broad lines are statistically disfavored.
• Figure 1 (top vs middle panels): Check timing between optical peak and any W1/W2 response to gauge dust reprocessing and consistency with a central, unobscured TDE.