Radio and X‐Ray Emission as Probes of Type IIP Supernovae and Red Supergiant Mass Loss

Type IIP (plateau) supernovae are thought to come from stars with initialmass about 8-25 solar masses that end their lives as red supergiants. Theexpected stellar end points can be found from evolutionary calculations and thecorresponding mass loss properties at this point can be estimated from typicalvalues for Galactic stars. The mass loss densities of observed supernovae canbe estimated from observations of the thermal X-ray and radio synchrotronemission that result from the interaction of the supernova with the surroundingwind. Type IIP supernovae are expected to have energy-conserving interactionduring typical times of observation. Because Type IIP supernovae have anextended period of high optical luminosity, Compton cooling can affect theradio emitting electrons, giving rise to a relatively flat radio light curve inthe optically thin regime. Alternatively, a high efficiency of magnetic fieldproduction results in synchrotron cooling of the radio emitting electrons. Boththe X-ray and radio luminosities are sensitive to the mass loss and initialmasses of the progenitor stars, although the turn-on of radio emission isprobably the best estimator of circumstellar density. Both the mass lossdensity and the variation of density with stellar mass are consistent withexpectations for the progenitor stars deduced from direct observations ofrecent supernovae. Current observations are consistent with mass being the onlyparameter; observations of a supernova in a metal poor region might show howthe mass loss depends on metallicity.Comment: 28 pages, 7 figures, ApJ, submitte