Astron. Astrophys. 358, 451-461 (2000)

Radio variability of the gamma-ray blazar 0202+149

T.B. Pyatunina ¹, S.G. Marchenko ^2,3, A.P. Marscher ³, M.F. Aller ⁴, H.D. Aller ⁴, H. Teräsranta ⁵ and E. Valtaoja <sup>6

1</sup> Institute of Applied Astronomy, Zhdanovskaya St. 8, 197110 St. Petersburg, Russia (ptb@ipa.rssi.ru)
² Astronomical Insitute, St. Petersburg State University, Bibliotechnaya pl. 2, 198904 St. Petersburg, Russia
³ Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA
⁴ Astronomy Department, University of Michigan, Ann Arbor, MI 48109, USA
⁵ Metsähovi Radio Research Station, Helsinki University of Technology, 02540 Kylmälä, Finland
⁶ Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland

Received 23 April 1999 / Accepted 11 February 2000

Abstract

Analysis of radio light curves of the -ray bright blazar 0202+149 at frequencies of 37, 22, 14.5, 8, and 4.8 GHz during the period 1984-1998 reveals a 4-year cycle of variability with substructure on a shorter time scale of about 1.3-yr. The 4.8-37 GHz spectral index of the source gradually increases from -0.04 (T=1990.2) to 0.4 (T=1996.6) and during outbursts shows strong variations with a time scale of about 1 year and an amplitude up to 0.4. VLBI images at 8, 22, and 43 GHz show a core-dominated structure with a faint jet in the northwest direction, which we trace out to 7 mas, with a bent inner part (1 mas) consisting of at least 2 components. The connection of the jet activity with the 4-year cycle of total flux density variability is discussed.

Key words: galaxies: active galaxies: quasars: individual: 0202+149 radio continuum: galaxies

Send offprint requests to: T.B. Pyatunina

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Contents

• 1. Introduction
• 2. Observations and reduction
  • 2.1. (a) Geodetic VLBI data
  • 2.2. (b) 22 and 43 GHz VLBA observations
• 3. Time scales of the radio variability
  • 3.1. Visual inspection
  • 3.2. Evolution of the total flux density spectrum
  • 3.3. Time series analysis
  • 3.4. Evolution of the spectral index
• 4. Structure of the VLBI jet
  • 4.1. Outer jet structure
  • 4.2. Inner jet structure
• 5. Superluminal motion
• 6. Flux density variations of the VLBI-components
• 7. Discussion
• 8. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000
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