This work provides an additional example of the hidden resources embedded in the Hipparcos observations. While the idea of studying the astrometric binaries from the absolute positions of the photocentre was put forth at an early stage during the mission design, the fact that the fiducial point observed through the modulating grid was not the system photocentre came much later after months of analysis of anomalous residuals of the astrometric processing. This opportunity has been fully exploited in this paper to determine for a handful systems the mass of each of the components and the individual brightness together with the parallax. For the remaining 37 close binaries with short periods, the introduction in the modelling of the orbital motion has allowed to derive a more accurate parallax than with the standard Hipparcos processing and to determine a function of the mass ratio and of the magnitude difference.
© European Southern Observatory (ESO) 1998
Online publication: January 16, 1998