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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
Abstract
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]](img1.gif)
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)
© European Southern Observatory (ESO) 1999
Online publication: December 2, 1999
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