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

Abstract

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 (Mr = −10.3 mag), SN 2017ivv shows an unprecedented evolution during the two years of observations. At early times, the light curve shows a fast rise (∼6 − 8 days) to a peak of ${\rm M}^{\rm max}_{g}= -17.84$ mag, followed by a very rapid decline of 7.94 ± 0.48 mag per 100 days 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 56Co (between 100 and 350 days), and another slower (after 450 days), probably produced by an additional energy source. From the bolometric light curve, we estimated that the amount of ejected 56Ni is ∼0.059 ± 0.003 M⊙. The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) Hα strong phase (<200 days); (2) Hα weak phase (between 200 and 350 days); and (3) Hα broad phase (>500 days). 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 – 17 M⊙.

Luminous Type II Short-Plateau Supernovae 2006Y, 2006ai, and 2016egz: A Transitional Class from Stripped Massive Red Supergiants

“…Dessart & Hillier (2020) also suggest a high M Hecore and low M Henv to better match the broad nebular line profiles (v Hα, FWHM 4200 km s −1 ; see also Dessart et al 2010). For SN 2017ivv, Gutiérrez et al (2020) estimate a M ZAMS of 15-17 M and note the transitional characteristics from SN II to IIb by analyzing the temporal evolution of the nebular line ratios. Following this line of reasoning, the nebular line ratios (and upper limits) and velocities of SN 2016egz likely suggest a similar partially stripped massive progenitor.…”

“…In Figure 12, we show the comparison of the nebular line ratios of SN 2016egz with a combined CCSN sample from Kuncarayakti et al (2015), Fang et al (2019), andGutiérrez et al (2020) and additional SN II We note that SN 2016egz as well as SNe 2015bs and 2017ivv lie in a somewhat transitional region between SNe II and eIIb-Ib (Figure 12). For SN II 2015bs, Anderson et al ( 2018) infer a high progenitor M ZAMS of 17-25 M based on the nebular line fluxes and velocities.…”

SN 2019hcc: a Type II supernova displaying early O ii lines

“…One such example is SN 2017ens (Chen et al 2018), a transition between a luminous broadline SN Ic and a SN IIn. SN 2017ivv is another, sharing properties with fast-declining SN II and SN IIb (Gutiérrez et al 2020), or SN 2014C, which underwent a change from a SN Ib to SN IIn due to interaction with a hydrogen-rich CSM (Milisavljevic et al 2015). Objects such as these can support physical continuity between progenitors and explosion mechanisms of different types (Filippenko 1988).…”

Modeling the signatures of interaction in Type II supernovae: UV emission, high-velocity features, broad-boxy profiles

“…This boxy emission extends to the red of the Hα rest wavelength and makes its origin clear : It only occurs in the presence of interaction (model NoPwr does not have it). Such a profile has been seen at nebular times in SN 2017ivv (Gutiérrez et al 2020).…”