SN 2009ip and SN 2010mc: Core-collapse Type IIn supernovae arising from blue supergiants

TL;DR

SN 2009ip and SN 2010mc are confirmed to be core-collapse Type IIn supernovae originating from blue supergiants, with spectral and light curve evidence supporting a terminal explosion rather than a non-terminal event.

Contribution

This study provides strong observational evidence that SN 2009ip and SN 2010mc are genuine core-collapse supernovae from blue supergiants, clarifying their nature and ruling out non-terminal explosion scenarios.

Findings

Spectral and light curve similarities confirm both are standard SNe IIn.

Late-time spectra resemble SN 1987A, supporting core-collapse origin.

Evidence suggests about half as much 56-Ni as SN 1987A was produced.

Abstract

The recent supernova (SN) known as SN 2009ip had dramatic precursor eruptions followed by an even brighter explosion in 2012. Its pre-2012 observations make it the best documented SN progenitor in history, but have fueled debate about the nature of its 2012 explosion --- whether it was a true SN or some type of violent non-terminal event. Both could power shock interaction with circumstellar material (CSM), but only a core-collapse SN provides a self-consistent explanation. The persistent broad emission lines in the spectrum require a relatively large ejecta mass, and a corresponding kinetic energy of at least 10^51 erg, while the faint 2012a event is consistent with published models of core-collapse SNe from compact (~60 R_Sun) blue supergiants. The light curves of SN 2009ip and another Type IIn, SN 2010mc, were nearly identical; we demonstrate that their spectra match as well, and that both are standard SNe IIn. Our observations contradict the recent claim that the late-time spectrum of SN 2009ip is returning to its progenitor's LBV-like state, and we show that late-time spectra of SN 2009ip closely resemble spectra of SN 1987A. Moreover, SN 2009ip's changing H-alpha equivalent width after explosion matches behavior typically seen in core-collapse SNe IIn. Several key facts about SN 2009ip and SN 2010mc argue strongly in favor of a core-collapse interpretation, and make a non-terminal 10^50 erg event implausible. The most straighforward and self-consistent interpretation is that SN 2009ip was an initially faint core-collapse explosion of a blue supergiant that produced about half as much 56-Ni as SN 1987A, with most of the peak luminosity from CSM interaction.