AstroNote 2023-250

We report the classification of the optical transient ZTF23aapyidj/AT2023mfm as a tidal disruption event (TDE). AT2023mfm was first detected by the Zwicky Transient Facility (ZTF) on 2023 June 18 at a magnitude of g = 19.88 +/- 0.17 mag. AT2023mfm was identified as a TDE candidate due to its blue color (g-r ~ -0.3 mag) for more than 30 days. 

We observed AT2023mfm on 2023 Sep. 07 UT with the Kast double spectrograph on the Shane 3 m telescope at Lick Observatory. The spectra (range 3500-10600 Angs) are dominated by a starlight continuum from an older stellar population with weak nebular emission lines at redshift z=0.087, diluted by a blue continuum. In comparison with galaxy templates, a broad emission feature is present near H-alpha, consistent with previous TDE spectra.

We requested and obtained one epoch of Swift observation on 2023 Aug 10. The host-subtracted UVOT (AB) photometry is uvw2=18.85 +/- 0.06 mag, uvm2=18.57 +/- 0.07 mag, and uvw1=18.45 +/- 0.06 mag, implying a UV-optical color of uvm2 - r ~ -0.1 mag. No significant X-ray emission was detected, with a 3-sigma 0.3-10 keV upper limit at <1.71E-3 count/s. Assuming an absorbed blackbody spectral shape with Nh=3.31E+20 cm^-2 and Tbb=80 eV, this corresponds to a luminosity limit of < 8.8E+41 erg s^-1.