# Talk abstract details

Asteroseismic model fitting - surface layer corrections and separation ratios
Ian W Roxburgh

### Abstract

We show that the frequency offset for the Sun is far better modelled by a polynomial rather than a simple Kjeldsen power law and argue that the offset should be treated as an unknown and determined as part of the model fitting procedure. We show that, in principle, the model with an $\ell$ independent surface correction whose frequencies best fit an "observed" set does not have the same internal structure as the "observed" star, but the difference is small.

The ratios of small to large separations seek to subtract off the unknown effect of the outer layers and hence by finding a best fit between models and observations gives a models whose interior structure best fits that of the observed star. We point out that the observed and model ratios should be compared at the same frequency - not the same $n,\ell$ values, and provide an algorithm for doing this.