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Session 45 - Supernovae.
Display session, Tuesday, January 14
Metropolitan Ballroom,

[45.14] Type Ia Supernovae: On the time evolution of the progenitor population

T. Tsujimoto, K. Nomoto (U. Tokyo), P. Hoeflich (U. Texas)

We investigate the question on the time evolution of the progenitor population of Type Ia Supernovae (SNe Ia). Time scales for the changes to be expected depend mainly on the progenitor masses of the donor stars, the metallicity, and the star formation rate of the host galaxy. We find a rather week the sensitivity to the the initial mass function. Actual accretion rates in the progenitor system are of minor importance. Our results are applied to elliptical galaxies which, in general, have stopped star formation at z \approx 1. In principle, a comparison with observations of SNe Ia at moderate redshifts (z \leq 1) provides a direct test of the progenitor evolution both by the implications on the SN Ia rate and, perhaps, systematic changes in the light curves and spectra. Alternatively, the local SN-rate in ellipticals can be compared with the observed rate in spiral galaxies. We find that the population of donor stars must include objects with masses down to at least 1.3 M_ødot with masses down to at least 1.3 M_ødot with \approx 1. M_ødot being more likely. In the latter case, the masses of the donor stars must rather broad. Consequently, we must expect a change of the statistical properties of the progenitor systems. The possible consequences for the use of Type Ia to determine the cosmological deceleration q_o are discussed.

Program listing for Tuesday