Young Supernovae as Experimental Sites to Study Electron Acceleration Mechanism

Abstract

Radio emissions from young supernovae (~ 1 year after the explosion) show a peculiar feature in the relativistic electron population at a shock wave, where their energy distribution is steeper than typically found in supernova remnants (SNRs) and than the prediction from the standard diffusive shock acceleration (DSA) mechanism. This is especially established for a class of stripped envelope supernovae (SNe IIb/Ib/Ic) where a combination of high shock velocity and low circumstellar material (CSM) density makes it easier to derive the intrinsic energy distribution than in other classes of SNe. We suggest that this apparent discrepancy reflects the situation that the low energy electrons before accelerated by the DSA-like mechanism are responsible for the radio synchrotron emission from young SNe, and that studying young SNe sheds light on the still-unresolved electron injection problem in the acceleration theory of cosmic rays. We suggest that electron's energy distribution could be flattened toward the high energy, most likely around 100 MeV, which marks a transition from inefficient to efficient acceleration. Identifying this feature will be a major advance in understanding the electron acceleration mechanism. We suggest two further probes: (1) mm/sub-mm observations in the first year after the explosion, and (2) X-ray observations at about 1 year and thereafter. We show that these are reachable by ALMA and Chandra for nearby SNe.

5 pages, 3 figures, accepted for publication in ApJL

References in corpus (6)

• Circumstellar Emission from Type Ib and Ic Supernovae
• An Early & Comprehensive Millimeter and Centimeter Wave and X-ray Study of Supernova 2011dh: A Non-Equipartition Blastwave Expanding into A Massive Stellar Wind
• Maximum synchrotron frequency for shock-accelerated particles
• Injection and Acceleration of Electrons at A Strong Shock: Radio and X-ray Study of Young Supernova 2011dh
• Probing Shock Breakout and Progenitors of Stripped-Envelope Supernovae through Their Early Radio Emissions
• Observations of the post shock break-out emission of SN 2011dh with XMM-Newton

Cited by in corpus (6)

• Continued radio observations of GW170817 3.5 years post-merger
• Long-Lasting X-Ray Emission from Type IIb Supernova 2011dh and Mass-Loss History of The Yellow Supergiant Progenitor
• The final months of massive star evolution from the circumstellar environment around SN Ic 2020oi
• A Multi-Wavelength View on the Rapidly-Evolving Supernova 2018ivc: An Analog of SN IIb 1993J but Powered Primarily by Circumstellar Interaction
• SN 2014C: VLBI image shows a shell structure and decelerated expansion
• Quasi-perpendicular shock acceleration and TDE radio flares