We present the results of global VLBI observations at 6 cm wavelength of the X-ray binary LSI+61◦303 made at epoch 1992.4. During the course of our 24 hour VLBI observing session, the integrated flux measured simultaneously with the VLA indicated that the source was experiencing a minor flare, with the total flux rising and falling by ∼ 12 mJy. Our VLBI observations indicate that this brighteni...

We report 18cm VLBI continuum imaging observations at ∼5 milliarcsecond resolution for UGC 5101, NGC 7469, and Mrk 231, all part of a sample of Luminous Infrared Galaxies which have been shown to have strong VLBI radio cores in a previous 18cm VLBI survey. Mrk 231, generally considered to be a dust-enshrouded QSO, shares many characteristics with quasars, including a broad, Sy1 optical emission...

We present pc-scale images of ten Compact Symmetric Objects (CSO) candidates observed with the European VLBI network (EVN). Five radio sources have been observed at 1.6 GHz, and five more at 2.3/8.4 GHz, the latter subsample with the inclusion in the VLBI array of 3 antennae normally used for geodesy. These objects were selected from existing samples of GHz Peaked Spectrum (GPS) radio sources w...

Context. The free core nutation (FCN) can be observed by its associated resonance effects on the forced nutations of the Earth’s figure axis, as observed by very long baseline interferometry (VLBI), or on the diurnal tidal waves, retrieved from the time-varying surface gravity recorded by superconducting gravimeters (SG). Aims. In this paper, we study the sensitivity of both techniques to the F...

Recent developments in Very Long Baseline Interferometry (VLBI) radio astronomy are aimed at improving reliability and reducing the cost of operations by moving from a custom made tape based system to using exchangeable disks in PCs. The advent of the iGRID 2002 exhibition in September 2002 with the availability of high data rate international links gave us the opportunity to try transferring t...

Astrometric accuracy of complex modern VLBI arrays cannot be calculated analytically. We study the astrometric accuracy of phasereferenced VLBI observations for the VLBA, EVN and global VLBI array by simulating VLBI data for targets at declinations −25◦, 0◦, 25◦, 50◦, 75◦ and 85◦. The systematic error components considered in this study are calibrator position, station coordinate, Earth orienta...

To determine the location of the intra-day variable (IDV) emission region within the jet of the BL Lac object S5 0716+714, a multi-epoch VSOP polarization experiment was performed in Autumn 2000. To detect, image, and monitor the short term variability of the source, three space-VLBI experiments were performed with VSOP at 5 GHz, separated in time by six days and by one day. Quasi-contemporaneo...

The atmosphere is surrounding the solid Earth and the oceans, and with its variations at time scales from seconds to decades it opens up a wide field of challenging and fascinating tasks in space geodesy. The investigation of these atmospheric effects and the analysis of geodetic Very Long Baseline Interferometry (VLBI) observations have dominated my research in the past decade. Geodetic VLBI w...

We present results from the first successful open call e-VLBI science run, observing the X-ray binary GRS1915+105. e-VLBI science allows the rapid production of VLBI radio maps, within hours of an observation rather than weeks, facilitating a decision for follow-up observations. A total of 6 telescopes observing at 5 GHz across the European VLBI Network (EVN) were correlated in real time at the...

We present results from the first successful open call e-VLBI science run, observing the X-ray binary GRS1915+105. e-VLBI science allows the rapid production of VLBI radio maps, within hours of an observation rather than weeks, facilitating a decision for follow-up observations. A total of 6 telescopes observing at 5 GHz across the European VLBI Network (EVN) were correlated in real time at the...