An Early & Comprehensive Millimeter and Centimeter Wave and X-ray Study of Supernova 2011dh: A Non-Equipartition Blastwave Expanding into A Massive Stellar Wind

TL;DR

This study provides a detailed early multi-wavelength analysis of supernova 2011dh, revealing non-equipartition shock physics and expanding into a stellar wind, with implications for understanding supernova classifications and early observations.

Contribution

First detailed early multi-wavelength study of supernova 2011dh revealing non-equipartition shock physics and expanding into a stellar wind environment.

Findings

Shockwave does not exhibit equipartition (e_e/e_B ~ 1000).

Supernova ejecta velocity is about 15,000 km/s, placing it between compact and extended SN IIb types.

Early high-frequency radio and X-ray observations are crucial for understanding supernova physics.

Abstract

Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN2011dh/PTF11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit equipartition (e_e/e_B ~ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R^-2. Within modeling uncertainties we find an average velocity of the fast parts of the ejecta of 15,000 +/- 1800 km/s, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast-wave regime between the previously defined compact and extended SN IIb subtypes. Our results highlight the importance of early (~ 1 day) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio e_e/e_B.