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Spectroscopic Classification of ASASSN-18zj with the Lick 3-m Shane Telescope

ATel #12198; Subo Dong, Subhash Bose, Ping Chen (KIAA-PKU), T. G. Brink, Thomas de Jaeger, A. V. Filippenko, and W. Zheng (UCB)
on 10 Nov 2018; 17:18 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Subo Dong (dongsubo@pku.edu.cn)

Subjects: Optical, Transient, Tidal Disruption Event

Referred to by ATel #: 12218

We report a spectroscopic observation of the optical transient ASASSN-18zj (as known as AT 2018hyz) performed on Nov. 9, 2018 UT with the Kast spectrograph mounted on the 3-m Shane telescope at Lick Observatory.

ASASSN-18zj (RA 10:06:50.875; Dec +01:41:33.96) was discovered by the All Sky Automated Survey for SuperNovae (ASAS-SN; Shappee et al. 2014; ATel #12194) on 2018-11-06.65 at g = 16.4 mag. According to ATel #12194, the position of ASASSN-18zj is within ~0.1” of the center of its host galaxy 2MASS J10065085+0141342 (redshift z = 0.045815, via NED), and its luminosity was approximately M_g = -20.2 mag at the time of discovery.

The Lick/Kast spectrum reveals a blue continuum with a broad (~10,000 km/s) H-alpha emission line and also weaker broad emission lines of (probably) H-beta and He I 5876 Angstrom (rest wavelength).

SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) shows good matches with young Type II supernovae.

The spectroscopic features are also similar to those of optical tidal disruption event (TDE) candidates such as ASASSN-14ae (Holoien et al. 2014). The SDSS archival spectrum of the host galaxy shows clear signatures of an E+A/post-starburst galaxy with the presence of H-alpha absorption and other strong Balmer absorption lines, including H-delta. Optical TDE candidates are known to have a clear preference for E+A/post-starburst galaxies (Arcavi et al. 2014; French et al. 2017). The transient's spectroscopic features, high luminosity, and location (consistent with the host-galaxy center), together with the E+A host, make ASASSN-18zj an excellent TDE candidate. Multiwavelength follow-up observations are strongly encouraged.