content_image/423964.jpg
<img src='content_image/423964.jpg'>

p is the power law index in the electron energy distribution N ( E ) = N 0 E . 

Note, that for the optically thin part of the synchrotron spectrum p = 1 − 2 α , where α is defined as S$_{ν}$ ∼ ν α . b 

The estimates correspond to the region of parsec-scale radio core. c 

The values are in the observer’s frame. d 

The homogeneous synchrotron source model is not applicable for this spectrum. 

## Acknowledgments 

K. Sokolovsky is supported by the International Max-Planck Research School (IMPRS) for Astron- omy and Astrophysics at the universities of Bonn and Cologne. T. Savolainen is a research fellow of the Alexander von Humboldt foundation. T. Savolainen also acknowledges support by the Academy of Fin- land grant 120516. Y. Kovalev was supported by the return fellowship of Alexander von Humboldt foun- dation and the Russian Foundation for Basic Re- search (RFBR) grant 08-02-00545. This research has been partially funded by the Bundesministerium f¨ ur Wirtschaft und Technologie under Deutsches Zentrum f¨ ur Luft- und Raumfahrt grant number 50OR0808. This work is based on data obtained from the National Radio Astronomy Observatory’s Very Long Baseline Array (VLBA), project BK150. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agree- ment by Associated Universities, Inc. This research has made use of NASA’s Astrophysics Data Sys- tem; the NASA/IPAC Extragalactic Database (NED) which is operated by the JPL, Caltech, under contract with the NASA, the SIMBAD database, operated at CDS, Strasbourg, France. The authors are grateful to E. Ros for reviewing this manuscript. 

## References 

1 Atwood W. B., et al., 2009, ApJ, 697, 1071 

2 Zensus J. A., 1997, ARA&A, 35, 607 

3 Savolainen T., Wiik K., Valtaoja E., Tornikoski M. 2008, ASPC, 386, 451 

4 Lobanov, A. P. 1998, A&AS,132, 261 

5 Napier P. J., 1994, IAUS, 158, 117 

6 Fomalont E., 1981, NRAON, 3, 3 

7 Shepherd M.C., Pearson T.J. and Taylor G.B. 1994, BAAS, 26, 987 

8 Kovalev, Y. Y., Lobanov, A. P., Pushkarev, A. B., & Zensus, J. A. 2008, A&A, 483, 759 

9 Lobanov, A. P. 1998, A&A, 330, 79 

10 Pacholczyk A.G. 1970, Radio astrophysics, San Francisco: Freeman 

11 Virtanen, J. J. P., & Vainio, R. 2005, ApJ, 621, 313 

12 Kovalev, Y. Y., et al. 2009, ApJL, 696, L17 

13 Marscher A.P. 1983, ApJ, 264, 296 

