EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 374/2 Article
Free access article

Issue A&A
Volume 374, Number 2, August I 2001
Page(s) 435 - 442
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20010754



A&A 374, 435-442 (2001)
DOI: 10.1051/0004-6361:20010754

Two-sided radio emission in ON 231 (W Comae)

E. Massaro1, F. Mantovani2, R. Fanti2, 3, R. Nesci1, G. Tosti4 and T. Venturi2

1  Dipartimento di Fisica, Università "La Sapienza", P.zle A. Moro 2, 00185 Roma, Italy
2  Istituto di Radioastronomia, CNR, Via P. Gobetti 101, 40129 Bologna, Italy
3  Dipartimento di Fisica, Università di Bologna, Via Irnerio 46, 40126 Bologna
4  Osservatorio Astronomico, Università di Perugia, Via A. Pascoli, 06100 Perugia, Italy

(Received 13 April 2000 / Accepted 17 May 2001 )

Abstract
Recent radio images of the BL Lac object ON 231 (W Com, 1219+285) show remarkable new features in the source structure compared to those previously published. The images were obtained from observations made with the European VLBI Network plus MERLIN at 1.6 GHz and 5 GHz after the exceptional optical outburst occurred in Spring 1998. The up-to-date B band historic light curve of ON 231 is also presented together with the R band luminosity evolution in the period 1994-1999. We identify the source core in the radio images with the brightest component having the flattest spectrum. A consequence of this assumption is the existence of a two-sided emission in ON 231 not detected in previous VLBI images. A further new feature is a large bend in the jet at about 10 mas from the core. The emission extends for about 20 mas after the bend, which might be due to strong interaction with the environment surrounding the nucleus. We suggest some possible interpretations to relate the changes in the source structure with the optical and radio flux density variation in the frame of the unification model.


Key words: BL Lacertae objects: general -- individual: ON 231

Offprint request: E. Massaro, massaro@astro.uniroma1.it

SIMBAD Objects



© ESO 2001


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.