4 juin - 7 juin 2013


S06 Astrométrie de haute précision et applications

Radio source structure and VLBI position instabilities

Romuald Bouffet, Patrick Charlot, Sébastien Lambert

Most of the extragalactic radio sources that materialize the International Celestial Reference Frame (ICRF) exhibit spatially-extended structures on milliarcsecond scales which limit the accuracy of the source positions estimated from VLBI data. These structures when varying with time may also lead to instabilities in the source positions. Structural variations are generally due to ejection of material from the VLBI core in a recurrent although unpredictable manner. Based on ten years of VLBI astrometric data acquired by the IVS (International VLBI Service for Geodesy and Astrometry) between 1994 and 2003 and source images produced over the same period on a bi-monthly basis, we compare position instabilities and structural variations for 68 sources and discuss the level of correlation between the two phenomena.