Rapid disk formation and reprocessing in a X-ray bright tidal disruption event
Abstract
We present UV/optical, X-ray and optical spectroscopic follow-up of a new X-ray bright tidal disruption event. The Swift lightcurve is atypical, showing a secondary maximum/plateau after 40-80 days of decline from peak, similar to ASASSN-15lh. In addition to broad H, He and potentially O/Fe lines, narrow emission lines emerge in the optical spectra during the plateau phase. We identify both high ionisation (He i and O iii) and low ionisation (Fe ii) lines. These lines, in conjunction with the Lopt/Lx ratio evolution, suggest the rapid formation of a compact accretion disk, which can be explained by a relativistic pericenter. We similarly identify Fe ii lines in optical spectra of ASASSN-15oi 330 d after discovery, indicating that a class of Fe-rich TDEs exists. Taken together with the plateau in X-ray and UV/optical luminosity this indicates that emission from the central source is efficiently reprocessed into UV/optical wavelengths, suggesting that we are witnessing the real-time assembly of an accretion disk around a SMBH. We will present the observations and their implications, and highlight some similarities between TDEs and NLS1 galaxies.
- Publication:
-
The Extragalactic Explosive Universe: the New Era of Transient Surveys and Data-Driven Discovery
- Pub Date:
- October 2019
- DOI:
- 10.5281/zenodo.3478116
- Bibcode:
- 2019eeu..confE..60W
- Keywords:
-
- Zenodo community eeu2019