A plea for better astrophysical and astrometric data in case of double stars of peculiar interest |
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Authors: | S Débarbat F Chollet |
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Institution: | (1) Observatoire de Paris, France |
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Abstract: | Summary TheIAU Symposium No. 61 (Perth, 1973, “New Problems in Astrometry’) makes clear that radiosources will play an important role for astrometry
in view of the linkage of reference systems.
The purposes developed later were to link the various systems from the earth and the solar system to the most inertial possible
one.
Extragalactic radiosources are the most reliable objects but they are faint. So, intermediate objects are needed. Among them
the radiostars, optical objects having radioemission at a certain level and for given frequencies have a fundamental and key
position.
Most of such radiostars are double or multiple ‘binaries’ as it can be seen from the list of reference stars issued by the
Working Group of Commission 24, Working Group created in 1978. The last issue of the core list of radiostars was presented
by Ch. de Vegt (Chairman of the WG) on the occasion of the last General Assembly of the IAU (November 1985).
A recent study of the system α Scorpii (Antares) has shown that the data concerning the magnitude and the spectral type are
not accurate enough, according to the accuracy obtained for the astrometric position (±0
.
s
003 for an astrolabe campaign in right ascension).
There is also a need for better knowledge about the orbits. In the case of the astrolabe observations, if the distance between
the components in <3″ the astrometric position concerns the photocenter and accurate physical properties are needed for comparison
with the radio position.
Better astrophysical properties are strongly needed for all radiostars to be used as references, during the time the astrometrists
have to improve the accuracy of their measurements both in optical and radio fields.
Presented by S. Débarbat. |
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Keywords: | |
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