Astron. Astrophys. 361, 770-780 (2000)
7. Conclusions
The main conclusions from this study are:
(1) The observed number of C and G solutions among the bright
( -8) main-sequence (spectral type
A) stars in the Hipparcos Catalogue
cannot be explained by assuming the same frequency and distribution of
binaries as found by Duquennoy & Mayor (1991) for nearby
solar-type stars. A significantly higher multiplicity is found, at
least for semi-major axes in the range 1-100 AU. The estimated
multiplicity in the 1-10 AU interval is
%, and in the 10-100 AU interval
it is %. With reasonable
extrapolations to other a this gives a total multiplicity of
0.9-1.2 companions per primary.
(2) The data are consistent with a decreasing mass-ratio
distribution (e.g., ) assumed for
all separations, but not with flat or increasing distributions.
(3) Assuming a distribution in
similar to the ones derived in this study (dashed curves in
Fig. 2), we predict three times as many orbital solutions (type
O) as given in the Hipparcos Catalogue for the corresponding stellar
sample. This indicates that many more orbital solutions could be found
by re-analysing the Hipparcos intermediate data, possibly with the aid
of new spectroscopic observations for the determination of
periods.
(4) The detection probability for binaries with
to 10 AU is 10-20 per
cent, if the curved motion of the photocentre is used to detect
duplicity. This applies, for Hipparcos, to stars at a median distance
of 100 pc. This is an interesting and generally difficult range
of separations that falls between the spectroscopic and the visual
binaries. Future astrometric projects such as GAIA should be able to
probe the same separation range at distances of several kpc.
© European Southern Observatory (ESO) 2000
Online publication: October 2, 2000
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