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Astron. Astrophys. 326, 77-86 (1997)

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Search for intraday radio variability in EGRET blazars

G.E. Romero * 1, 2, J.A. Combi 1, 2, P. Benaglia [FORMULA] 1, I.N. Azcárate ** 1, J.C. Cersosimo 3 and L.M. Wilkes 3

1 Instituto Argentino de Radioastronomía, C.C.5, (1894) Villa Elisa, Bs. As., Argentina
2 Theoretical Physics Lab, Department of Physics, University of La Plata, C.C. 64, 1900 La Plata, Argentina
3 University 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 [FORMULA] 7 % over timescales of [FORMULA] 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

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© European Southern Observatory (ESO) 1997

Online publication: April 20, 1998