TESS eclipsing binaries apsidal motion

To extend the time baseline, we combine the high-precision TESS timings with reliable archival data. On the other hand, for each component of our sample of double-lined eclipsing binaries we computed grids of evolutionary stellar models for the observed stellar mass exploring ranges of values of the overshooting parameter, fov, the mixing-length parameter and the metallicity. To find the best solution for the two components we adopt a chi-squared statistic to infer the optimal values of the overshooting parameter and the mixing-length parameter.

The theoretical internal structure constants to be compared with the observed values were calculated by integrating the differential equations of Radau for each stellar model. We have determined the apsidal motion rate of 27 double-lined eclipsing binaries with precise physical parameters. The obtained values, corrected for their relativistic contribution, yield precise empirical parameters of the internal stellar density concentration.

The comparison of these results with the predictions based on new theoretical models shows very good agreement. Small deviations are identified but remain within the observational uncertainties and the path for a refined comparison is indicated.