Large outbursts in Cygnus X-3

Abstract

Two radio outbursts in Cyg X–3 were observed during December 1973 and January 1974. The source was observed at 4.2 GHz using the 26-m radio telescope of Kashima Branch of the Radio Research Laboratories, which has a half power beamwidth of 10 arc min. Flux densities were obtained using drift scan so as to avoid interference from HII regions surrounding Cyg X-3. An average of four or five scans was taken to determine the flux densities. The receiver gain was calibrated during each determination using the output from a noise tube. It was also calibrated at five hour intervals by observing 3C147 (assumed flux density 9.3 Jy—1 Jansky=1 f.u.—) and 3C274 (80 Jy) in December 1973, and 3C123 (19.0 Jy) in January 1974. We measured the total flux densities alternately in orthogonal planes of polarisation by rotating the polariser, except on December 23 and 24, 1973. On those occasions the flux densities were measured in only one plane of polarisation. The pointing accuracy was checked frequently by the scans with declination offset. The error in flux density is less than 0.3+0.05S_4.2 Jy, where S_4.2 is the flux density at 4.2 GHz.