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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.
| Absolute dimensions of eclipsing binaries. XIII - AI Pheonicis: A case study in stellar evolution
The masses, radii, and chemical composition of evolved F + K-typeeclipsing binary AI Phe are redetermined. The masses for the stars are1.20 solar for the hotter, less-evolved star, and 1.24 solar for thecooler, larger subgiant component. The orbital eccentricity is e = 0.188+ or - 0.002. The metal abundance of AI Phe is determined to be (Fe/H) =-0.14 + or - 0.1, corresponding to Z = 0.012 + or - 0.003. New stellarevolution sequences are computed with the VandenBerg (1983) code for theobserved masses of the two components, for a helium abundance that isrequired to satisfy the luminosity constraints of the data, and for avalue of the mixing-length parameter that has been calibrated from asolar model. These models fit the observed properties of AI Phe withremarkable precision. The success of standard evolution theory inmodeling AI Phe strongly suggests that convective overshooting isunimportant in stars with masses near 1.25 solar.
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