Effects of opacity on stellar radii and their relavance to observational data

Abstract

We have examined the effect of varying opacities on envelope structure with the aid of Paczynski #8217;s public domain stellar modelling programs. For this, we prepared new opacity tables from the data of Kurucz[1], using Lagrange interpolation to obtain the tabular values. We compare the results of these Kurucz opacities with similar tabulations from Huebner et al. [2],Iglesias and Rogers [3],Rogers and Iglesias [4]and Iglesias and Rogers [5].We have checked calculations for the same ranges of stars considered originally by Schwarzschild [6],and compared our findings, using newer opacity data, with those of other sources. We consider how such calculations relate to high accuracy observational data,with the well-observed planetary eclipsing system V 376 Peg (HD209458), providing a guideline towards data of similar accuracy in the near future. Current accuracies on absolute radii and masses derivable from eclipsing spectroscopic binaries are conservatively estimated at ~1%. The effects of revised opacity calculations on the radii of stars of intermediate mass are several times greater than this(5 #8211;10 % for constant values of other parameters) ,so that eclipsing binary data should have good potential for independent tests of opacity theory across a wide range of stellar types.