AT2020ocn/ZTF18aakelin: Tidal Disruption Event that is Brightening in the X-rays
ATel #13859; S. Gezari (UMd), S. van Velzen (UMd/NYU), D. Stern (Caltech), S. Frederick (UMd), E. Hammerstein (UMd), C. Ward (UMd), S. B. Cenko (NASA/Goddard), and M. Graham (Caltech), on behalf of the ZTF Collaboration
on 10 Jul 2020; 14:46 UT
Credential Certification: Suvi Gezari (suvi@astro.umd.edu)
Subjects: Optical, Ultra-Violet, X-ray
We report the classification of AT2020ocn/ZTF18aakelin as a tidal disruption event (TDE) in the quiescent, early type galaxy SDSS J135353.80+535949.7 at z=0.0705. The optical transient was first detected by the ZTF MSIP Northern Sky Survey on 2020 April 29 with g = 20.51 +/- 0.23 mag, and rose to a peak on 2020 May 09 with g=19.8 +/- 0.2 mag. Our Swift follow-up observations reveal that the nuclear transient is also UV bright, with Swift UVOT observations measuring uvw2 ~ 19.3 mag over the last two weeks, while the optical transient has faded to g~20.3 mag. We obtained a spectrum on 2020 Jun 17 with the Palomar 200in DBSP which revealed a blue excess compared to the archival SDSS spectrum, and evidence for broad emission near He II 4686, consistent with the TDE classification.
We also report dramatically brightening soft X-ray emission, from the first Swift XRT observation on 2020 Jun 25 with a count rate of 0.0069 +/- 0.0026 cts/sec, to the most recent Swift XRT observation on 2020 Jul 10 with a count rate of 0.0375 +/- 0.0051 cts/sec, all in the 0.3-1.5 keV band. The latest XRT count rate corresponds to a flux of 2.87e-12 ergs/s/cm^2 and a luminosity of 3.5e43 ergs/s, assuming a typical TDE blackbody temperature of 0.06 keV.
We will continue Swift monitoring, and have triggered VLA observations. Further spectroscopic follow-up and X-ray observations are encouraged.
