*Astron. Astrophys. 330, 585-599 (1998)*
## 3. Important points of the data processing
### 3.1. General management
The practical implementation of the processing is briefly described
in Paper I, Sect. 4.2. There is a double iterative process:
the first one consists in improving the reference values
at the step *i* by injecting the solutions
obtained at step ; the second one corresponds
to the iterative filtering of the largest residuals found in this
step. The data of the 145 selected objects have first been processed
by an *all purpose* algorithm, quite similar to the one used for
the simulation. However the poor overall quality of the results has
shown that a specific processing adapted for each star was preferable.
One of the most crucial points to ensure the convergence of the
processing was the choice of the threshold to filter out the residuals
and this had to be fine-tuned on a case by case basis alongside the
weighing of the observations.
### 3.2. The reference values of and *B*
As it was mentioned in Paper I, Sect. 4.2, the equations
relating the Hipparcos observations on the circle to the astrometric
and physical parameters are all non-linear. Thus, it is useful to
start the processing with input values of and
*B* relatively good. It turns out that for all the cases
presented in this paper, the magnitude difference is fairly well known
and this was sufficient to compute an input . On
the other hand, for more than half of the systems, no reliable input
value of the mass ratio *B* has been found (see Table 9). In
this case the mass luminosity relation for dwarf stars has been used
to yield an approximate first guess of *B* via the
expression,
where and are the
masses of the components.
### 3.3. The choice of an orbit
For many of the systems, there are more than one set of orbital
elements proposed in the literature. We have tested systematically all
the possible orbits for each object and then selected a particular set
of orbital elements. The selection criteria were based on the quality
of the fit (Unit Weight Variance), the number of required iterations
and the stability of the solutions to a small perturbation of the
input values and of the orbital elements. For most of the cases, the
selected orbit (see Tables 4 - 5) happens to be the most recent
one. It must also be noted that the elements derived from the speckle
interferometry were particularly satisfactory, regarding their
adequation to the Hipparcos data.
© European Southern Observatory (ESO) 1998
Online publication: January 16, 1998
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