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Astron. Astrophys. 338, 840-842 (1998)

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2. Observations, calibration and data reduction

The observation took place on 23-24 February 1997 with 7 antennas of the European VLBI Network (EVN) at 5 GHz. Parameters of the radio telescopes are shown in Table 1. 3C287 was observed over 10.5 hours using left circular polarization. Data were recorded with MkIII recording system in mode B, which results in 28 MHz bandwidth. Correlation took place at the Max Planck Institute for Radio Astronomy in Bonn, Germany.


Table 1. EVN telescopes involved in the experiment and their characteristics at 5 GHz
a) system equivalent flux density
b) the telescope was used in phased array mode; an equivalent diameter is given.

Initial data calibration was done using the NRAO AIPS package (Cotton 1995; Diamond 1995). Instrumental delay errors were corrected using 0804+499 calibrator source which is unresolved with the western EVN. The data were fringe-fitted in AIPS using 13 minutes solution time. We used the measured antenna system temperatures and gains for initial amplitude calibration, while complex bandpasses were calibrated using 0804+499. Data were averaged using 1 minute integration time. The Caltech DIFMAP package (Shepherd et al. 1994) was used for self-calibration and imaging. First a preliminary image was made with the western EVN antennas using a point source starting model. The clean components of this map formed the starting model of the final imaging process involving the whole dataset.

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© European Southern Observatory (ESO) 1998

Online publication: September 17, 1998