Late-Time Radio Detection of the TDE AT2018fyk

ATel #16650; Yvette Cendes (University of Oregon/ CfA), Edo Berger (CfA), Kate Alexander (University of Arizona), Tanmoy Laskar (University of Utah), Adelle Goodwin (Curtin University)
on 13 Jun 2024; 14:39 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Yvette Cendes (yvette.cendes@cfa.harvard.edu)

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We report the discovery of late-time radio emission from the TDE AT2018fyk with the MeerKAT radio telescope at 1.36 GHz. AT2018fyk/ ASASSN-18ul (RA: 22:50:16.090, Dec: -44:51:53.50) was first detected by the All Sky Automated Survey for Supernovae (ASASSN) on September 8, 2018 at a distance of 270 Mpc (Wevers 2019). The TDE was UV and X-ray bright for the first 500 days. Subsequent dimming at 600 days and rebrightening at 1200 days in X-rays have led to speculation that AT2018fyk could be a partial TDE (Wevers 2023). In radio, several ATCA observations in the first ~600 days post-discovery at 21 GHz and 7.5 GHz yielded non-detections (Wevers 2019, Wevers 2021). We first observed AT2018fyk with MeerKAT on May 8, 2021 (days since disruption, t_d = 973 days) at 1.36 GHz resulting in a 3sigma upper limit of <0.06 mJy (Cendes 2024, in press). A subsequent L-band MeerKAT observation on January 25, 2023 (t_d = 1601 days) resulted in a 3sigma upper limit of <0.04 mJy (Cendes 2024, in press). However, a recent L-band MeerKAT observation on Feb 20, 2024 (t_d = 1991 days; program: SCI-20230907-YC-01) resulted in a clear detection of AT2018fyk of 0.087 +/- 0.013 mJy at 1.36 GHz, indicating a brightening by a factor of at least 2x in ~1 year. A subsequent observation on May 15, 2024 (t_d = 2086 days; DDT-20240522-YC-01) yielded a detection of 0.0531 +/- 0.0131 mJy. Further observations with MeerKAT and ATCA are ongoing; multi-wavelength observations (particularly in X-ray) are encouraged. We thank the MeerKAT observatory and staff for coordinating these observations.