AstroNote 2021-310

We report new radio observations taken as part of our VLA Large Program dedicated to tidal disruption events (TDEs). Following its public classification by ZTF (TNS Classification Report No. 10352), we have been observing the TDE AT2021sdu with NSF’s Karl G. Jansky Very Large Array (VLA), beginning on 2021 August 10 UT. The data were reduced in CASA using standard procedures. We detect brightening radio emission consistent with the optical position, with a peak flux density of ~0.7 mJy at ~18 GHz in our most recent multi-frequency observation on 2021 November 28 UT. The spectral index is consistent with self-absorbed synchrotron emission at lower frequencies. We additionally observed the target with the NICER X-ray telescope on 1 Dec 2021. The source was not detected and we set an upper limit on the 0.3-2.0 keV unabsorbed flux of 4e-13 erg/s/cm^2, assuming a 0.1 keV thermal spectrum. Further observations are planned. We encourage additional multi-wavelength follow up of this interesting source.

Our VLA Large Program (20B-377) began in December 2020 and will continue until 2023. We plan to target new publicly-reported TDEs discovered at z < 0.1, to determine the prevalence of radio emission in TDEs. We will report new results from this program to the community via ATels, TNS AstroNotes, and on our program website (https://sites.northwestern.edu/radiotdes/). For collaboration, or to suggest new targets, please contact the program PI (Kate Alexander, kate.alexander@northwestern.edu) or one of the program co-Is.