SN 2018aad Might be Another iPTF14hls at z=0.025
ATel #12135; I. Arcavi (Tel Aviv U.), D. Hiramatsu (Las Cumbres Obs./UCSB), S. W. Jha (Rutgers), J. Burke, D. A. Howell, C. McCully (Las Cumbres Obs./UCSB), S. Valenti (UC Davis)
on 20 Oct 2018; 20:25 UT
Credential Certification: Iair Arcavi (arcavi@gmail.com)
Subjects: Optical, Supernovae, Transient
SN 2018aad (ASASSN-18eo; Nicholls et al. 2018, ATel #11391) was classified as a Type II supernova at z=0.01 (Hosseinzadeh et al. 2018, TNSCR 1784) based on a broad H-alpha P-Cygni feature. Later spectra indeed show typical Type IIP SN features but the narrower lines allow a better redshift determination at z=0.025. This redshift puts the light curve peak at an absolute magnitude of ~-19, which is atypically high for Type IIP SNe. We find an expansion velocity of 8000 km/s for H-alpha (from the minimum of the P-Cygni absorption trough) at >200 days post discovery, which is also atypically high for a Type IIP SN at that stage. Superfit (Howell et al. 2005, ApJ, 634, 1190) finds matches to this H-alpha velocity with Type IIP SNe just 15-20 days post explosion. In addition, the light curve declined from a broad peak or plateau but ~50 days ago seems to have flattened and started rising again. All of these characteristics, together with a faint host galaxy, are similar to what was seen for the very peculiar supernova iPTF14hls (Arcavi et al. 2017, Nature, 551, 210). Additional followup of SN 2018aad at all wavelengths is strongly encouraged.
