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**Session 90 - Supernovae, Supernovae Remnants and Planetary Nebulae.**

*Oral session, Wednesday, January 17*

*Salon del Rey Central, Hilton*

## [90.01] Cosmological Distances from Spectral Analysis of Supernova Photospheres

*M. J. Montes (Stanford Dept. of Physics and CSSA)*

Type II supernovae provide an excellent opportunity to probe various
properties of the universe. Their relative
physical simplicity allows us
to calculate model spectra by invoking well understood physics.

We perform a semi-analytic calculation of the continuum spectra
of type II supernovae. This is an extension of the approximate
radiative transfer analysis of Hershkowitz, Linder and Wagoner to a
more general class of model atmospheres, using a simple fit to the
continuum opacity produced by lines. The atmosphere is characterized by
an effective temperature, a radial power-law dependence of the density
of hydrogen, and less strongly by the heavy element abundance and
velocity gradient.
We match asymptotic expressions for the spectral energy density at the
photosphere, whose location at each frequency is determined by a first
order calculation of the deviation of the mean intensity from the
Planck function. The emergent spectral luminosity then assumes the
form of a diluted blackbody, and the major result is
the dependence of this frequency dependent dilution factor upon the
temperature and radius of the photosphere, as well as the power-law
index of the hydrogen density distribution.

These results are used to determine the power law indices for several
supernovae. We compare our dilution factors to those of Schmidt, Kirshner and
Eastman. The comparison of the dilution factors allows us to
estimate the distances we obtain compared to distances obtained by SKE.

**Program
listing for Wednesday**