AstroNote 2024-43

AT2022dbl was classified as a tidal disruption event (TDE) at z=0.0284 on 2022 Feb 21 (AstroNote 2022-47; Arcavi et al. 2022). ZTF observations show that the TDE rose to a peak magnitude of g~17 around 2022 Mar 2 and has subsequently faded and stayed at g>21 mag from November 2022 to December 2023. 

On 2024 Jan 12, ZTF detected AT2022dbl again at g=19.20 +/- 0.13 mag. The g-band light curve gradually brightened and reached g=17.92 +/- 0.06 mag on 2024 Feb 1, suggesting a possible re-brightening of this TDE. On 2024 Feb 5, we obtained an optical spectrum using the Keck-I/LRIS. The spectrum is similar to that from the first TDE flare from 2 years ago, with a blue continuum and broad lines around He II and Halpha. 

Seven epochs of Swift observations have been triggered and obtained during the second flare. The UVOT data show that the second flare is bright and rising in the UV, with the host-subtracted uvw2 AB magnitude being 18.1 on 2024 Jan 23 and 17.4 on 2024 Feb 3. No significant X-ray emission was detected by XRT. The merged XRT event file (14.4 ks) gives a 3-sigma upper limit of 4.88e-4 c/s, which corresponds to 1.7e-14 erg/cm^2/s assuming an absorbed power-law with Gamma=2 and Galactic nH=1.94e+20 cm^-2.

If the two optical flares are from the disruption of the same star, AT2022dbl might represent a repeating partial TDE (pTDE), similar to the previously identified pTDE AT2020vdq (Somalwar et al. 2023, arxiv: 2310.03782). Follow-up observations of AT2022dbl at all wavelengths are encouraged.