Volume 375, Number 2, August IV 2001
|Page(s)||661 - 669|
|Section||Atomic, molecular, and nuclear data|
|Published online||15 August 2001|
Stability of the extragalactic VLBI reference frame*
Observatoire de Paris/CNRS UMR8630, 61 Av. de l'Observatoire, 75014, Paris, France
2 Institut Géographique National/LAREG, 8 Av. Blaise Pascal, Champs sur Marne, 77455 Marne la Vallée Cedex 2, France
3 US Naval Observatory, code EO, Massachusetts Avenue, NW, Washington, DC 20392-5420, USA
Corresponding author: A.-M. Gontier, Anne-Marie.Gontier@obspm.fr
Accepted: 1 March 2001
The qualification and the maintenance of the International Celestial Reference Frame (ICRF) source directions are currently based on global statistics regarding the complete data set of VLBI observations of extragalactic radio sources. The founding hypothesis in the selection of extragalactic objects to access a quasi-inertial reference system is that their directions are fixed in space. Therefore the study of the time variability of the sources is an important step in the process of checking and improving the reliability of the ICRF, in view of high precision applications such as Earth rotation studies or the unification with future space astrometry results. In this paper we investigate the systematic and random behaviours in time series of individual determinations of coordinates for several hundred sources over 1987-1999. New criteria for the qualification of sources in a future revision of the ICRF are proposed.
Key words: galaxies: quasars: general / techniques: interferometric / astrometry / reference systems
© ESO, 2001
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