AstroNote 2022-223

We report the discovery and classification of ZTF22abajudi/AT2022lri, a UV and X-ray bright tidal disruption event (TDE) in a galaxy at z=0.032. 

AT2022lri is a nuclear transient first reported to TNS by the ATLAS survey on 2022 June 2 with o=17.2. Forced photometry recovered subthreshold ATLAS detections in March 2022. We note that the rise of the optical flare was missed by optical sky surveys due to Sun constraints. AT2022lri was subsequently detected by the Zwicky Transient Facility (ZTF; Bellm et al. 2019; Graham et al. 2019) Caltech survey on 2022 August 14 with g=18.77 +/- 0.04 mag. It passed the ZTF nuclear filter (van Velzen et al. 2019, 2021) on 2022 Sep 17. The optical flux has since slowly declined.

We obtained an optical spectrum with the Double Spectrograph (DBSP) on the Palomar 200-inch telescope on 2022 October 11 which showed host galaxy features at z=0.032 and broad lines around Halpha and He II 4686 at the same redshift. This classifies AT2022lri as a TDE-H+He, following the classification scheme in van Velzen et al. 2021 and Hammerstein et al. 2022.

We triggered a Swift observation which was obtained on 2022 October 23 with an exposure time of 2.13 ks. The X-ray telescope (XRT) detected an X-ray source with 0.569 +/- 0.017 count/s. An absorbed blackbody (tbabs*zbbody) model fit to the XRT spectrum suggests a blackbody temperature of 114 +/- 5 eV, and a 0.3--2 keV flux of (1.34 +0.07 -0.05) e-11 erg/cm^2/s, corresponding to a luminosity of (3.2 +/- 0.2) E+43 erg/s. The Ultraviolet telescope (UVOT) detected a bright UV source with (host galaxy subtracted) uvw2=18.52 +/- 0.04 mag. The UV flux is bright with uvw2 ~ r-1. 

Continued monitoring with Swift and the NICER X-ray telescope (GO program 5035; PI Yao) have been triggered. Further multi-wavelength follow-up observations are encouraged.

We thank the Swift team for the prompt approval and execution of our TOO observation.