Statistical Investigation on Radio Supernovae with Markov Chain Monte Carlo Analysis

Tomoki Matsuoka^1*, Keiichi Maeda², Shigeo Kimura³, Masamoi Tanaka³

¹Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
²Department of Astronomy, Kyoto University, Kyoto, Japan
³Astronomical Institute, Tohoku University, Sendai, Japan

* Presenter:Tomoki Matsuoka, email:tmatsuoka@asiaa.sinica.edu.tw

Radio emission from supernovae (radio SNe) is attributed to synchrotron radiation from electrons accelerated by an SN shock interacting with circumstellar medium (CSM). Radio SNe has a unique potential to trace CSM density structure that can be translated into mass-loss histories of massive stars before the explosion, as well as to estimate efficiencies of electron acceleration and magnetic field amplification. Here we present the result of a systematic investigation of 35 radio SNe with the unified model through Markov chain Monte Carlo (MCMC) analysis. We find the inferred mass-loss rate of stripped-envelope SN progenitors is by an order of magnitude greater than that of SN II progenitors, with temporal evolution roughly constant. The efficiencies of electron acceleration and magnetic field amplification in some radio SNe are not comparable with each other, but the possibility of equipartition is not still ruled out. On the other hand, we find two properties that are not reasonable in terms of the standard model for radio SNe; one is the extremely high magnetic field amplification efficiency, and the other is the shallower density gradient of the outer ejecta. We suggest the new interpretation that these peculiar results are misled due to the setup that is not included in our model, and we identify the missing setup as a dense CSM in the vicinity of the progenitor. This means that a large fraction of radio SN progenitors may possess dense confined CSM that is not smoothly connected with outer CSM.

Keywords: supernovae, massive stars, cosmic-ray acceleration