Astron. Astrophys. Suppl. Ser. 130, 299-304

CCD astrometry and UBV photometry of visual binaries

II. Visual double stars with mainly G - type primaries and relatively small angular separation

D. Sinachopoulos - E. van Dessel

Royal Belgian Observatory, Ringlaan 3, B-1180 Ukkel, Brussels, Belgium

Received October 16; accepted December 8, 1997

Abstract:

Differences $\Delta V$ of magnitude and $\Delta (B{-}V)$ and $\Delta (U{-}B)$ colours, as well as separations and position angles of 42 relatively close double stars are presented. The selection criteria of our sample are: the relatively small separation (between 2.5 and 5 arcseconds), magnitude difference under 1.25 mag, and mainly G-type primaries. The CCD observations, performed at the 90 cm Dutch telescope at ESO, were made using the Bessel U, B and V filters; the astrometry was done in the V filter only.

From the analysis of the photometric data we conclude that 16 binaries in our sample have components with practically the same $T_{\rm eff}$, since they have almost the same colours; one binary has components with identical characteristics. We also note the good internal accuracy of the astrometric CCD measurements.

Key words: stars: binaries: visual -- astrometry