FLOYDS Classification of AT 2018dyk/ZTF18aajupnt as a Possible Tidal Disruption Event

ATel #11953; I. Arcavi, J. Burke (Las Cumbres Obs./UCSB), K. D. French (Carnegie), A. Zabludoff (U of Arizona), D. Hiramatsu, C. McCully, D. A. Howell, G. Hosseinzadeh (Las Cumbres Obs./UCSB), S. Valenti (UC Davis)
on 15 Aug 2018; 01:05 UT
Credential Certification: Iair Arcavi (iarcavi@lcogt.net)

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We obtained a spectrum of the nuclear transient AT 2018dyk/ZTF18aajupnt on 2018 August 12.3 UT with the robotic FLOYDS instrument mounted on the Las Cumbres Observatory 2-meter telescope on Haleakala, Hawai'i, under the "Transients in Galaxy Centers" program (PI: Arcavi). Using Superfit (Howell et al. 2005, ApJ, 634, 1190), we find a reasonable fit to the tidal disruption event (TDE) ASASSN-14ae (Holoien et al. 2014, MNRAS, 445, 3263; Arcavi et al. 2014, ApJ, 793, 38) at the redshift of the host galaxy (z=0.037; SDSS). The spectrum displays possible broad H-alpha, H-beta and He II emission lines, similar to those seen in other TDEs. Unlike other TDEs, however, it displays narrow H-beta and He II emission lines not seen in the SDSS host spectrum, stronger narrow H-alpha compared to the SDSS host spectrum, and it does not display a blue continuum. The ZTF light curve retrieved from the ZTF public alert stream via MARS (https://mars.lco.global/7014426/) peaks at an apparent magnitude of about 18.6, which at the deduced redshift corresponds to an absolute magnitude of -17.4, several magnitudes fainter than most TDEs but similar to the TDE iPTF16fnl (Blagorodnova et al. 2017, ApJ, 844, 46). The SDSS spectrum of the host galaxy shows weak H-alpha emission indicative of only weak current star formation, and does not show strong Balmer absorption which would be indicative of a recent strong starburst. The recent star formation history of the host galaxy appears similar to that of TDE PTF09ge (Arcavi et al. 2014, ApJ, 793, 38), which formed less than 1% of its current stellar mass in the last Gyr (French et al. 2016, ApJL, 818, 21; French et al. 2017, ApJ, 835, 176). Our spectrum is available on the Transient Name Server.