Vikram V. Dwarkadas

We summarize the X-ray emission from young SNe. Having accumulated data on most observed X-ray SNe, we display the X-ray lightcurves of young SNe. We also explore the X-ray spectra of various SN types. The X-ray emission from Type Ib/c SNe is non-thermal. It is also likely that the emission from Type IIP SNe with low mass-loss rates (around 10$^{-7} \, Msun \,$ yr$^{-1}$) is non-thermal. As the mass-loss rate increases, thermal emission begins to dominate. Type IIn SNe have the highest X-ray luminosities, and are clearly thermal. We do not find evidence of non-thermal emission from Type IIb SNe. The aggregated data are used to obtain approximate mass-loss rates of the progenitor stars of these SNe. Type IIP's have progenitors with mass-loss rates $< 10^{-5}\, Msun \,$ yr$^{-1}$, while Type IIn progenitors generally have mass-loss rates $> 10^{-3}\, Msun $ yr$^{-1}$. However, we emphasize that the density of the ambient medium is the important parameter, and if it is due to a non-steady outflow solution, it can not be translated into a mass-loss rate.