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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Simultaneous analysis of light and radial velocity curves of the peculiar contact system V 508 Ophiuchi
BV observations of V 508 Oph obtained between 1984 and 1987 and newtimes of minimum are presented. A complete study of minima publishedsince 1943 allows to detect a likely increase of the period by about0.003 s per year. The new versions of the Wilson-Devinney syntheticmethod is employed to analyze simultaneously the BV photometry and theradial velocity curves for both components of the system. Absolutevalues for masses, luminosities, and radii are determined in that way.The results show that V 508 Oph is a nontypical member of the A-type WUMa binaries, because of its large mass-ratio (q = 0.53) and its lowdegree of overcontact (about 10 percent). The striking behavior ofpreviously observed light curves might roughly be explained by means ofa blue selective emission zone located between both components of thesystem.
| Program of Parallax Measurements from Space for the Nearest Eclipsing Binaries
Not Available
| The peculiar behaviour of the photometric variability of V508 Ophiuchi
Recent UBV observations of the eclipsing binary V508 Oph are presented.The obtained partial light curves show the typical behaviour of W UMasystems. The amplitudes of light variation are about 0m.80,0m.86, and 0m.94 in V, B, and U, respectively.This is not consistent with older photographic and photoelectric BV datawhich showed amplitudes of about 0m.6 and 1m.1 inV and B. Furthermore, the shapes of the light curves are not similar tothe older ones. It is concluded that a strong change in the photometricbehaviour of V508 Oph has probably occurred between 1981 and 1984.
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