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SALT Spectroscopic classification of Three Transients

ATel #12246; Subhash Bose, Subo Dong, Ping Chen (KIAA-PKU), M. Gromadzki (Warsaw), D. A. H. Buckley (SAAO), Jose L. Prieto (UDP), Jack M. Neustadt, K. Z. Stanek (OSU), T. Holoien (Carnegie)
on 29 Nov 2018; 11:52 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Subo Dong (dongsubo@pku.edu.cn)

Subjects: Optical, AGN, Supernovae, Transient, Tidal Disruption Event

We report spectroscopic observations of optical transients ASASSN-18zz (ATel #12228), ASASSN-18zp (ATel #12194) and ATLAS18yik using SALT/RSS (350.0-920.0 nm). The target was discovered by All-Sky Automated Survey for Supernovae (ASAS-SN, Shappee et al. 2014) and ATLAS survey (Tonry et al. 2011 and Tonry et al. ATel #8680). We used SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) to identify the SN type, phase, and redshift from the spectra.

 
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 Survey Name | IAU Name   | Obsv. Date    | Spec. Type  | Phase                 |  Redshift     | Notes  
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 ASASSN-18zz | SN 2018ioa | 2018-11-23.03 |    Ia       | ~ 1 week post-max.    | 0.041229(NED) | (a)   
 ATLAS18yik  | SN 2018hzh | 2018-11-23.13 |    Ia       | ~10 days post-max.    | 0.035         |    
 ASASSN-18zp | SN 2018ido | 2018-11-23.32 |   AGN/TDE?  | ---                   | 0.052997(NED) | (b)   
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(a) The redshift is of the host galaxy from NED. The SNID estimated redshift is consistent with that of the host galaxy.
(b) The spectrum shows strong and broad hydrogen Balmer emission lines. In addition, there are weak and broad HeI and possibly HeII emission lines. ASASSN-18zp was discovered on the rise on UT 2018-11-08 at an absolute magnitude of M_g = -19.5 mag. Relative astrometry using an image taken by LCOGT 1m telescope shows that ASASSN-18zp is located at 0.08 +/- 0.11 arcsec with respect to the nucleus position of the host galaxy 2dFGRS S448Z231. The archival 2dF spectrum (via NED) of the host shows broad H-alpha line (FWHM of broad component ~ 4000 km/s) and strong [N II] 6584 line with respect to H-alpha (log10([N II]/Halpha) ~ 0.3), suggesting that it is an AGN. We note that there was a reported X-ray flare of the host detected in 2011 (ATel #3516). This nuclear transient is very likely due to AGN activity, or another possibility is a TDE candidate occurring in an AGN.