SN 2017ivv: two years of evolution of a transitional Type II supernova

Gutierrez, C. P.; Pastorello, A.; Jerkstrand, A.; Galbany, L.; Sullivan, M.; Anderson, J. P.; Taubenberger, S.; Kuncarayakti, H.; Gonzalez-Gaitan, S.; Wiseman, P.; Inserra, C.; Fraser, M.; Maguire, K.; Smartt, S.; Muller-Bravo, T. E.; Arcavi, I; Benetti, S.; Bersier, D.; Bose, S.; Bostroem, K. A.; Burke, J.; Chen, P.; Chen, T-W; Della Valle, M.; Dong, Subo; Gal-Yam, A.; Gromadzki, M.; Hiramatsu, D.; Holoien, T. W-S; Hosseinzadeh, G.; Howell, D. A.; Kankare, E.; Kochanek, C. S.; McCully, C.; Nicholl, M.; Pignata, G.; Prieto, J. L.; Shappee, B.; Taggart, K.; Tomasella, L.; Valenti, S.; Young, D. R.
2020
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
DOI
10.1093/mnras/staa2763
We present the photometric and spectroscopic evolution of the Type II supernova (SN II) SN 2017ivv (also known as ASASSN-17qp). Located in an extremely faint galaxy (M-r =-10.3 mag), SN 2017ivv shows an unprecedented evolution during the 2 yr of observations. At early times, the light curve shows a fast rise (similar to 6-8 d) to a peak of M-g(max) = -17.84 mag, followed by a very rapid decline of 7.94 +/- 0.48 mag per 100 d in the V band. The extensive photometric coverage at late phases shows that the radioactive tail has two slopes, one steeper than that expected from the decay of Co-56 (between 100 and 350 d), and another slower (after 450 d), probably produced by an additional energy source. From the bolometric light curve, we estimated that the amount of ejected 5(6)Ni is similar to 0.059 +/- 0.003M(circle dot). The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) H alpha strong phase (<200 d); (2) H alpha weak phase (between 200 and 350 d); and (3) H alpha broad phase (>500 d). We find that the nebular analysis favours a binary progenitor and an asymmetric explosion. Finally, comparing the nebular spectra of SN 2017ivv to models suggests a progenitor with a zero-age main-sequence mass of 15-17M(circle dot).