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Astron. Astrophys. 333, 199-204 (1998)

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Discovery of apsidal motion in [FORMULA] Coronae Borealis by means of ROSAT X-ray eclipse timing

Jürgen H.M.M. Schmitt

Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany

Received 12 August 1997 / Accepted 3 December 1997


Four ROSAT X-ray observations of the secondary optical minimum of the eclipsing binary system [FORMULA] CrB taken in 1992, 1993 and 1997 are presented. Because of the totality of the X-ray eclipse, the times of mid eclipse can be accurately determined from the ROSAT data. The period between secondary minima [FORMULA] is found to be significantly different from the optically well determined period between primary minima [FORMULA], thus indicating apsidal motion. The observed value [FORMULA] = 4.8 [FORMULA] 2.1 seconds is, first, shown to be almost exclusively due to the primary component, and second, consistent with our current knowledge of [FORMULA] CrB A. The relativistic contribution to the observed value is 0.95 seconds or 17 % of the total effect.

Key words: stars: coronae – stars: activity – binaries: eclipsing – stars: fundamental parameters – - stars: individual: ff CrB

Send offprint requests to: J.H.M.M. Schmitt (jhs@rosat.mpe-garching.mpg.de)

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© European Southern Observatory (ESO) 1998

Online publication: April 15, 1998