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Session 99 - Supernovae & Supernova Remnants.
Oral session, Friday, January 09

[99.02] Circumstellar and Interstellar Environments of Supernovae of Different Types and some Astrophysical Applications.

F. R. Boffi (STScI)

In my Thesis I have studied the environments of historical supernovae (hereafter SN/SNe), of different types, observationally, backed up with theoretical modelling of the local hydrodynamic interactions. The properties of the SNe environments were used to provide information about the SNe themselves and their stellar progenitors.

The radio emission produced by the hydrodynamical interaction of the SN ejecta with the circumstellar environment can be used to derive clues on the pre--supernova star system, i.e. can be used as a test of SN progenitor systems. We have predicted the radio emission of different SNe and found that 1) relatively nearby SNe Ia like SN 1986G, if they are coming from symbiotic systems, should be detectable by deep early radio observations 2) the Type II SNe 1984E and 1986E do not show detectable radio emission: the former SN, near its optical maximum, was interacting with a circumstellar shell that resulted from a preexplosion mass-loss episode of limited duration; the latter, instead, is the first ``old'' SN to have been detected in the optical and not in the radio. We have also studied the temporal evolution of the radio emission of a Type II SN exploding in a binary system and found that it differs from the single system scenario.

In the interstellar medium around SNe, instead, light echoes produced by the scattering of the supernova light by dust can be used to determine extragalactic distances geometrically (Sparks 1994, 1996). Ground-based imaging observations have been carried out designed to find light echoes. A number of promising candidates are found, showing present day optical emission visible at the sites of the historical supernovae, and these may be light echoes suitable for follow-up observations to determine the galaxy distances.

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