Research Information System
Conference of the NATO-Advanced-Study-Institute on Variable Stars as Essential Astrophysical Tools, CESME, Turkey, 31 August - 10 September 1998, vol.544, pp.577-585
Eclipsing binary system DI Her has an apsidal motion and its observed apsidal advance seems to be less than even the relativistic advance. Therefore many debates are centered about DI Her, which may also be extended to more or less similar systems showing such a discrepancy between the theory and the observations. Computed value of the apsidal motion rate from the eclipse timings of DI Her, up to now, is very small and about one fourth of the relativistic advance. In this work we show that such a small observed rate is due to use of visual and photographic data having low precision, and due to disregarding the large orbital eccentricity of the system. As a result, we found that the observed apsidal advance is still less than the relativistic advance, but is larger than the previous results by a factor of about two.