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Astron. Astrophys. 326, 77-86

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Search for intraday radio variability in EGRET blazars

G.E. Romero1,2,*, J.A. Combi1,2, P. Benaglia1,*, I.N. Azcárate1,**, J.C. Cersosimo3, and L.M. Wilkes3

1Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Bs. As., Argentina
2Theoretical Physics Lab, Department of Physics, University of La Plata, C.C. 64, 1900 La Plata, Argentina
3University of Puerto Rico, Humacao Campus, Department of Physics and Electronics, CUH Station, Humacao, PR 00791

Received 26 February 1997 / Accepted 17 April 1997


We present results of intraday variability observations at 5 GHz of the EGRET blazars 0202+14, 0235+16, 2230+11, and 2251+15. The BL-Lac object 0235+16 presented flux density variations of ~ 7% over timescales of ~ 1.3 days. The source 0202+14 was also variable, although with smaller amplitudes. The behaviour of 0235+16 at short timescales is almost identical to that presented in previous intraday observations carried out in 1990, when the flux density of the source was 4 times higher. We discuss the possible origin of the ultra rapid radio variability in these sources within different possible scenarios.

Key words: radio continuum: galaxies - galaxies: active

* Now at Instituto Astronômico e Geofísico (IAG). Univesidade de São Paulo, Av.M. Stefano 4200, CEP 04301-904 São Paulo, SP, Brazil
**Member of CONICET

Send offprint requests to: J.A. Combi, first address

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 20, 1998