Variability investigation of quasars 4C38.41 and 3C345 at 92cm: additional 14 observations

Abstract

This paper provides additional evidence for the variability of the quasar 4C 38.41 based on 14 short observations at 92 cm using the Westerbork Synthesis Radio Telescope (WSRT). A fractional variability of 11.6 per cent was observed during the periods of 1989 May and from 1992 December to 1993 May. A brightness temperature of TB∼2.6 or 5.2×1018δ−3 K in 4C 38.41 can be estimated in the comoving frame, far in excess of the inverse Compton limit 1012 K. A Doppler factor of δ⩾138 would be required by invoking the relativistic bulk motion. Combining the published six Westerbork North Sky Survey (WENSS) mosaic data at 92 cm, we conclude that 4C 38.41 has significant variability, which is unlikely to be caused by propagation effects. No variability was found for the quasar 3C 345.