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Astron. Astrophys. 352, L107-L110 (1999)

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Letter to the Editor

A change in the variability properties of the intraday variable quasar 0917+624

A. Kraus 1, A. Witzel 1, T.P. Krichbaum 1, A.P. Lobanov 1, B. Peng 1,2 and E. Ros 1

1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2 Beijing Astronomical Observatory, National Astronomical Observatories, Chinese Academy of Science, Beijing 100012, P.R. China

Received 12 October 1999 / Accepted 8 November 1999


We observed the quasar 0917+624 at three epochs at a wavelength of 6 cm in order to study its short-timescale variability. In December 1997 and February 1999, the source showed its usual characteristics: variations on a 10-15 % level have been found on timescales [FORMULA] days. In contrast, in September 1998 the source exhibited a monotonic increase of about 7 % during a five-day-observing campaign. Assuming an intrinsic origin of the variations, this corresponds to a change in brightness temperature of at least two orders of magnitude. We discuss shortly several mechanisms which may cause the observed change of the variability properties of 0917+624.

Key words: galaxies: active – galaxies: quasars: individual: 0917+624 – radio continuum: galaxies

Send offprint requests to: A. Kraus (akraus@mpifr-bonn.mpg.de)

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© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999