A non-equipartition shockwave traveling in a dense circumstellar environment around SN 2020oi

Assaf Horesh, Itai Sfaradi, Mattias Ergon, Cristina Barbarino, Jesper Sollerman, Javier Moldon, Dougal Dobie, Steve Schulze, Miguel Pérez-Torres, David R.A. Williams, Christoffer Fremling, Avishay Gal-Yam, Shrinivas R. Kulkarni, Andrew O’Brien, Peter Lundqvist, Tara Murphy, Rob Fender, Justin Belicki, Eric C. Bellm, Michael W. CoughlinEran O. Ofek, V. Zach Golkhou, Matthew J. Graham, Dave A. Green, Thomas Kupfer, Russ R. Laher, Frank J. Masci, A. A. Miller, James D. Neill, Yvette Perrott, Michael Porter, Daniel J. Reiley, Mickael Rigault, Hector Rodriguez, Ben Rusholme, David L. Shupe, David Titterington

Research output: Contribution to journalArticlepeer-review


We report the discovery and panchromatic followup observations of the young Type Ic supernova, SN 2020oi, in M100, a grand design spiral galaxy at a mere distance of 14 Mpc. We followed up with observations at radio, X-ray and optical wavelengths from only a few days to several months after explosion. The optical behaviour of the supernova is similar to those of other normal Type Ic supernovae. The event was not detected in the X-ray band but our radio observation revealed a bright mJy source (Lν ≈ 1.2 × 1027erg s1Hz1). Given, the relatively small number of stripped envelope SNe for which radio emission is detectable, we used this opportunity to perform a detailed analysis of the comprehensive radio dataset we obtained. The radio emitting electrons initially experience a phase of inverse Compton cooling which leads to steepening of the spectral index of the radio emission. Our analysis of the cooling frequency points to a large deviation from equipartition at the level of (formula presented) & 200, similar to a few other cases of stripped envelope SNe. Our modeling of the radio data suggests that the shockwave driven by the SN ejecta into the circumstellar matter (CSM) is moving at ∼ 3×104 km s1. Assuming a constant mass-loss from the stellar progenitor, we find that the mass-loss rate is (formula presented) for an assumed wind velocity of 1000 km s1. The temporal evolution of the radio emission suggests a radial CSM density structure steeper than the standard r2.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Jun 24 2020

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