SIMBAD references

DI Her is a double-lined eclipsing binary presenting a very slow apsidal motion for which the relativistic contribution is of the order of the newtonian one. The observed apsidal motion is around 4 times that predicted by stellar evolutionary models and by General Relativity. This trend is known for non-relativistic systems although in a minor scale. The magnitude of such a disagreement led some authors to propose several mechanisms to explain it, including a revision of the gravitation theory. In this paper some aspects of these processes are analyzed using modern stellar models, recent absolute dimensions and apsidal motion rate. New alternative explanations for the problem as for example, the intrinsic observational difficulties to obtain very slow apsidal motion rates with confidence, are also introduced.