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

Search for intraday radio variability in EGRET blazars

G.E. Romero ^{* 1, 2}, J.A. Combi ^{1, 2}, P. Benaglia ¹, I.N. Azcárate ^{** 1}, J.C. Cersosimo ³ and L.M. Wilkes <sup>3

1</sup> 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

Abstract

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

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
• 3. Results
• 4. Behaviour on larger timescales
• 5. Intraday variability
  • 5.1. Shocks
  • 5.2. Superluminal microlensing
  • 5.3. Refractive effects
• 6. Final comments
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: April 20, 1998
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