AstroNote 2022-106

AT2022dbl was discovered by ALeRCE on MJD 59688.28 == 2022-04-19.28 and we independently detected it in ATLAS on MJD 59689.37== 2022-04-20.37. The ATLAS forced photometry shows a 15-day rise with the last deep non-detection occuring on MJD 59683.40 == 2022-04-14.40. The transient peaked at g =16.4, c = 16.7 on MJD 59699 == 2022-04-30 and is very blue, with a g-r = -0.7 +/- 0.1. AT2022dbl is coincident (within 0.1") with the core of the host galaxy SDSS J095445.24+552625.2 which has a photoZ = 0.124 +/- 0.0114 and gives a peak absolute magnitude of M_g = -22.3 (assuming M-m = 38.7 and A_g = 0.03).

A spectrum was obtained on MJD 59705.92 == 2022-05-06.92 with SPRAT at the Liverpool Telescope. The spectrum is a blue continuum with apparent broad features at 4560A, 4690A and 5150A, which suggests the presence of He II and N III. Furthermore, we obtain matches with the known TDE-He AT2022dsb at around peak using SNID and therefore believe AT2022hvp to also be of the TDE-He subtype. The redshift from the SNID template matching is z = 0.12, consistent with the photometric redshift of the host. Host emission lines are not readily visible, and the galaxy appears red and quiescent.

We conclude that AT2022hvp is a fast-rising, very luminous and blue TDE, and the most likely classification is TDE-He, but that TDE-H+He is possible with very broad and shallow H-lines. We encourage spectroscopic follow-up.