Raffaella Margutti edited section_Radio_Observations_as_Probes__.tex  over 8 years ago

Commit id: 52f52d2bccc5116220bd26e376964db850cf8988

deletions | additions      

       

\section{Radio Observations as Probes of Pre-SN Massloss}  The radio emission in SNe is powered by synchrotron emission due to shock-accelerated relativistic electrons gyrating in the post-shock magnetic field. The synchrotron self-absorption (SSA) or free-free absorption (FFA) at low frequencies results in a spectral turnover. The evolution of the spectral peak frequency and luminosity directly depend on the density of the environment and radius of the blast-wave. Thus, by monitoring the evolution of the radio emission resulting from the SN shock interaction with the medium, it is possible to map the density of the environment sampled by the shock. Since the SN shock is typically $\geq 30$ times faster than the progenitor stellar wind, the radio emission from a SN shock effectively acts as a time machine and allows us to sample the pre-SN life of the stellar progenitor in the centuries before the explosion. X-rays and radio emission from the SN shock interaction with the medium are currently the \emph{only} probes to sample this phase of evolution of evolved stars. We focus on the radio wavelength range as it offers the most homogeneous data set with observations covering the early- and late-time evolution of Ib/c SNe. Motivated by the current discovery of strong interaction in an otherwise ordinary Ib SN at late times ($t>100$ days), here we propose the analysis of the entire data set of radio observations of core-collapse SNe and the self-consistent hydrodynamical modeling of the emission, with the goal to map the mass-loss history of evolved massive stars in the centuries before explosion, a territory that has been poorly sampled so far.