EDP Sciences
Free Access
Volume 383, Number 2, February IV 2002
Page(s) 533 - 539
Section Formation, structure and evolution of stars
DOI https://doi.org/10.1051/0004-6361:20011729
Published online 15 February 2002

A&A 383, 533-539 (2002)
DOI: 10.1051/0004-6361:20011729

Apsidal motion and light-time effect in eclipsing binaries HS Herculis and U Ophiuchi

M. Wolf1, P. Harmanec1, 2, R. Diethelm3, K. Hornoch1 and P. Eenens4

1  Astronomical Institute, Charles University Prague, 180 00 Praha 8, V Holesovickách 2, Czech Republic
2  Astronomical Institute, Academy of Sciences, 251 65 Ondrejov, Czech Republic
    e-mail: hec@sunstel.asu.cas.cz
3  Astronomical Institute, University of Basel, Venusstrasse 7, 4102 Binningen, Switzerland
    e-mail: diethelm@astro.unibas.ch
4  Departamento de Astronomia, Universidad de Guanajuato, Apartado 144, 36000 Guanajuato, Gto, Mexico
    e-mail: eenens@astro.ugto.mx

(Received 22 October 2001 / Accepted 30 November 2001)

Several new times of minima, based on photoelectric observations, have been secured for two bright and well-known eclipsing binaries with eccentric orbits and with very similar orbital periods: HS Her ( $P = 1\fd637, e = 0.02$) and U Oph ( $P = 1\fd677, e = 0.003$). For HS Her, an apsidal motion with a period of 78 years is confirmed and a third body in an eccentric orbit with a period of 85 years is found. An analysis of all available eclipse timings of U Oph has confirmed the presence of an apsidal motion with one of the shortest known periods (20.1 yr) and a light-time effect with the improved period of 37.6 yr. The corresponding internal structure constants log k2 were also derived. It is estimated that the tertiaries of both systems are detectable via speckle interferometry.

Key words: stars: binaries: eclipsing -- stars: individual: HS Her -- stars: individual: U Oph -- stars: fundamental parameters

Offprint request: M. Wolf, wolf@mbox.cesnet.cz

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© ESO 2002

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