SN 2016coi (ASASSN-16fp): an energetic H-stripped core-collapse supernova from a massive stellar progenitor with large mass loss

G. Terreran; R. Margutti; D. Bersier; J. Brimacombe; D. Caprioli; P. Challis; R. Chornock; D. L. Coppejans; Subo Dong; C. Guidorzi; K. Hurley; R. Kirshner; G. Migliori; D. Milisavljevic; D. M. Palmer; J. L. Prieto; L. Tomasella; P. Marchant; A. Pastorello; B. J. Shappee; K. Z. Stanek; M. D. Stritzinger; S. Benetti; L. Demarchi; N. Elias-rosa; C. Gall; J. Harmanen; S. Mattila

doi:10.3847/1538-4357/ab3e37

paper

SN 2016coi (ASASSN-16fp): an energetic H-stripped core-collapse supernova from a massive stellar progenitor with large mass loss

arXiv:1905.02226 · doi:10.3847/1538-4357/ab3e37

Abstract

We present comprehensive observations and analysis of the energetic H-stripped SN 2016coi (a.k.a. ASASSN-16fp), spanning the $γ$ -ray through optical and radio wavelengths, acquired within the first hours to $\sim$ 420 days post explosion. Our campaign confirms the identification of He in the SN ejecta, which we interpret to be caused by a larger mixing of Ni into the outer ejecta layers. From the modeling of the broad bolometric light curve we derive a large ejecta mass to kinetic energy ratio ( $M_{ej} \sim 4 - 7 M_{⊙}$ , $E_{k} \sim 7 - 8 \times 1 0^{51} erg$ ). The small [\ion{Ca}{ii}] \lam\lam7291,7324 to [\ion{O}{i}] \lam\lam6300,6364 ratio ( $\sim$ 0.2) observed in our late-time optical spectra is suggestive of a large progenitor core mass at the time of collapse. We find that SN 2016coi is a luminous source of X-rays ( $L_{X} > 1 0^{39} erg s^{- 1}$ in the first $\sim 100$ days post explosion) and radio emission ( $L_{8.5 G H z} \sim 7 \times 1 0^{27} erg s^{- 1} H z^{- 1}$ at peak). These values are in line with those of relativistic SNe (2009bb, 2012ap). However, for SN 2016coi we infer substantial pre-explosion progenitor mass-loss with rate $M ˙ \sim (1 - 2) \times 1 0^{- 4} M_{⊙} y r^{- 1}$ and a sub-relativistic shock velocity $v_{s h} \sim 0.15 c$ , in stark contrast with relativistic SNe and similar to normal SNe. Finally, we find no evidence for a SN-associated shock breakout $γ$ -ray pulse with energy $E_{γ} > 2 \times 1 0^{46} erg$ . While we cannot exclude the presence of a companion in a binary system, taken together, our findings are consistent with a massive single star progenitor that experienced large mass loss in the years leading up to core-collapse, but was unable to achieve complete stripping of its outer layers before explosion.

arXiv commentSubmitted to ApJ. Main text: 21 pages; Appendix: 15 pages; 12 figures

SN 2016coi (ASASSN-16fp): an energetic H-stripped core-collapse supernova from a massive stellar progenitor with large mass loss

Abstract

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