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Astron. Astrophys. 355, 552-563 (2000)

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2. Observations

The pair of radio sources 1038+528 A and B was observed with the NRAO Very Long Baseline Array (VLBA) on November 10, 1995, for a total of 13 hours, alternating every 13 minutes between observations in dual 3.6/13 cm mode and observations at 2 cm. The 100m telescope at Effelsberg was also included in the array for the 3.6/13 cm scans. The primary beamwidths of all the antennas were sufficiently large that both sources could be observed simultaneously at all wavelengths. Each 10 minute observation of 1038+52A,B was preceded by a 3 minute observation of the compact calibration source 0917+624, to monitor the behaviour of the array.

All stations used VLBA terminals to record an aggregate of 64 MHz bandwidth for each scan, using 1-bit sampling, subdivided into 8 channels (mode 128-8-1). For the dual 3.6/13 cm scans, four 8-MHz channels were recorded for each band (2254.5-2286.5 MHz; 8404.5-8436.5 MHz), using RHC polarisation. At 2 cm, eight 8-MHz channels (15 331.5-15 395.5 MHz) were recorded in LHC polarisation.

The correlation was made at the VLBA correlator in Socorro (New Mexico). As for previous epochs, two separate "passes" were needed, using different field centres for the two sources, to recover data for both the A and B quasars from the single observation. Output data sets were generated for the two sources, consisting of the visibility functions averaged to 2 s, with samples every 1 MHz in frequency across the bands.

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© European Southern Observatory (ESO) 2000

Online publication: March 9, 2000
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