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Session 97 - Supernovae.
Oral session, Wednesday, January 17
Salon del Rey Central, Hilton
It is now well established that thermonuclear explosions of white dwarfs are consistent with observations of Type Ia supernovae (SN Ia). The details of the actual explosions are not yet clear, in part because the nature of the supernova progenitor systems -- how the white dwarfs reach instability -- is essentially unknown. No progenitor system has been observed, and because SN Ia are rare (only one per galaxy is typically observed), population statistics are fraught with difficulties.
We would like to have a sample of, say, several hundred SN Ia, or their remnants, in a well studied galaxy in order to compare their distribution with those of various stellar populations. We suggest that we already have this survey (although line-of-sight integrated) for the Galaxy -- from the electron-positron annihilation radiation. We argue that SN Ia provide, via their radioactive positron emitters, a large fraction of the observed positrons, that the positrons annihilate very near the explosion sites, and thus, after subtraction of positrons from other sources, provide a direct Galaxy-wide tracer of SN Ia progenitors. This does not yet uniquely identify the progenitor systems, but it does place important constraints on some of the many proposed, especially ruling out any young population as a dominant contributor.
