The apsidal motion of the eccentric eclipsing binary DI Herculis - an apparent discrepancy with general relativity.

Abstract

DI Her is an important system for studying relativistic apsidal motion because of the large masses and small fractional radii of its components, the large orbital eccentricity and its relatively short period, and the favorable orientation of its orbital plane to our line of sight producing deep eclipses. In addition, the long history of eclipse timings provides an extended baseline for studying the motion of the line of apsides. However, as shown in this study, the analysis of the eclipse timings indicates that the observed advance of the periastron is nearly one-seventh that expected from Newtonian and relativistic effects. Thus, in DI Her, we are confronted with the puzzling situation of having either an undiscovered or misunderstood classical effect present in the system, or an inconsistency with general relativity.