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Keywords:

  • astrometry;
  • stars: binaries: close;
  • binaries: visual;
  • techniques: photometric

Abstract

We present relative astrometry and differential photometry measurements for a sample of nearby southern orbital binaries making use of the technique of Adaptive Optics. The observations were made in December 2000, with the ADONIS camera mounted at the 3.6-m ESO telescope from La Silla Observatory, equipped with the broad-band near-infrared filters (J -, H -, K -passbands). Our sample contains stars which do not fit very well the empirical mean mass-luminosity relation (according to our previous study), but for which accurate parallaxes (determined by the Hipparcos satellite) and high-quality orbits were available thanks to many previous efforts. We derived accurate positions and J, H, K magnitudes of the individual components of those binaries. The individual stellar components have near-infrared colour indices well grouped in those plots and are comparable to standard single stars. The data reduction procedure used for deriving those results is described in detail. It is based on a least-squares fit of Moffat-Lorentz profiles in direct imaging for well-resolved systems and on Fourier analysis for very close pairs. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)