Electron Cooling in a Young Radio Supernova: SN 2012aw

Abstract

We present the radio observations and modeling of an optically bright Type II-P supernova (SN), SN 2012aw which exploded in the nearby galaxy Messier 95 (M95) at a distance of $10\mathrm{Mpc}$. The spectral index values calculated using $C$, $X$ & $K$ bands are smaller than the expected values for optically thin regime. During this time the optical bolometric light curve stays in the plateau phase. We interpret the low spectral index values to be a result of electron cooling. On the basis of comparison between Compton cooling timescale and Synchrotron cooling timescale we find that inverse Compton cooling process dominates over synchrotron cooling process. We therefore model the radio emission as synchrotron emission from a relativistic electron population with a high energy cutoff. The cutoff is determined by comparing the electron cooling time scale $t_{cool}$ and the acceleration time scale ${\tilde{t}}_{acc}$. We constrain the mass loss rate in the wind ($\dot{M}\sim 1.9\times 10^{-6}{\mathrm{M}}_{\odot }\mathrm{y}{\mathrm{r}}^{-1}$) and the equipartition factor between relativistic electrons and the magnetic field ($\tilde{\alpha }={\epsilon }_e/{\epsilon }_B\sim 1.12\times 10^2$) through our modeling of radio emission. Although the time of explosion is fairly well constrained by optical observations within about $2\mathrm{days}$, we explore the effect of varying the time of explosion to best fit the radio light curves. The best fit is obtained for the explosion date as 2012 March 15.3 UT.

10 Figures, 2 Tables, Accepted for Publication in The Astrophysical Journal

References in corpus (7)

• BVRI lightcurves of supernovae SN 2011fe in M101, SN 2012aw in M95, and SN 2012cg in NGC 4424
• On Absorption by Circumstellar Dust, With the Progenitor of SN2012aw as a Case Study
• Supernova 2012aw - a high-energy clone of archetypal type IIP SN 1999em
• An Early & Comprehensive Millimeter and Centimeter Wave and X-ray Study of Supernova 2011dh: A Non-Equipartition Blastwave Expanding into A Massive Stellar Wind
• The Long-Lived UV "Plateau" of SN 2012aw
• The progenitor of SN 2011ja: Clues from circumstellar interaction
• X-Ray emission from SN 2004dj: A Tale of Two Shocks

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