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ZTF19acymzwg Unlikely Related to SRG/eROSITA X-ray TDE Candidate

ATel #13507; S. Gezari (UMd), S. van Velzen (UMd), Charlotte Ward (UMd), S. Frederick (UMd), K. De (Caltech), S. Kulkarni (Caltech), M. J. Graham (Caltech), and S. B. Cenko (NASA/Goddard) on behalf of the ZTF Collaboration
on 20 Feb 2020; 00:00 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Suvi Gezari (suvi@astro.umd.edu)

Subjects: Optical, AGN, Black Hole, Transient, Tidal Disruption Event

Referred to by ATel #: 13510

ATel #13494 reported the association of Zwicky Transient Facility alert ZTF19acymzwg with the SRG/eROSITA X-ray TDE candidate SRGet J143359.25+400638.5 detected centered on the galaxy SDSS J143359.16+400636 on 2019 Dec 27, and coincident with the X-ray source detected by Swift XRT on 2020 Feb 05 (ATel #13464). We have inspected the ZTF alert packets for ZTF19acymzwg, and note that the transient is significantly off-center from the host galaxy nucleus, by more than 1.0 arcsec in the g and r bands. We speculate that the transient, detected first by ZTF with g=19.3 mag on UT 2019 Dec 14 and then faded monotonically to g=20.5 mag on UT 2020 Jan 24, is in fact a supernova in the host galaxy that is unrelated to the SRG/eROSITA X-ray source.

We also obtained a spectrum of the host galaxy nucleus with Keck/LRIS on UT 2020 Feb 18, and confirm the presence of strong narrow emission lines at z=0.099 as also reported in ATel #13500, and we note that the line ratios of [O III]/Hbeta and [N II]/Halpha are in the Seyfert region of the BPT diagram. The AGN classification for the host galaxy optical spectrum, together with the relatively hard spectrum of the X-rays reported by SRG/eROSITA (kT = 0.29 keV compared to previously reported X-ray selected TDEs with 0.04 keV < kT < 0.17 keV), suggest that the X-ray variability may be related to the host galaxy AGN, and not a tidal disruption event.