DI Herculis as a test of internal stellar structure and general relativity. New apsidal motion rate and evolutionary models.
Abstract
For the past three decades there has been a serious discrepancy between the observed and theoretical values of the apsidal motion rate of the eccentric eclipsing binary DI Her, which has even been interpreted occasionally as a possible failure of general relativity. New times of minimum have been collected and used for redetermining of the apsidal motion rate.
Based on the latest determinations of the absolute dimensions of the binary, we computed new stellar evolution models with updated physical inputs, and derived improved apsidal motion constants for the components. We performed Monte Carlo simulations to infer the theoretical distribution of ω, including the contributions from GR, as well as tidal and rotational distortions.
This is in excellent agreement with the newly measured value of +0.00042 deg cycle-1. The formal difference is now reduced to 10%, a small fraction of the observational uncertainties.