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EVN observations of the radio galaxy M87 following a TeV flare

ATEL # 2437; M. Giroletti (INAF/IRA), G. Giovannini (Univ. of Bologna), M. Beilicke (Washington Univ.), A. Cesarini (NUI), H. Krawczynski (Washington Univ.)
on 13 Feb 2010; 10:16 UT
Password Certification: Marcello Giroletti (

Subjects: Radio, >GeV, AGN, Black Holes

We report on EVN observations of the radio galaxy M87, taken at 5 GHz on 2010 Feb 10. Data were acquired by 7 radio telescopes from 21:40 UT on Feb 10 to 8:30 UT on Feb 11, directly streamed to the central data processor at JIVE, and correlated in real-time (eVLBI). This permits us to promptly report on the status of the radio jet of the source, following the increase in gamma ray emission above 100GeV reported by MAGIC (ATel #2431)

The observations have an angular resolution of about 7 mas x 3 mas and rms noise of 0.12 mJy/beam. Preliminary analysis reveals a compact 1.73 Jy/beam core, and a more than 200 mas long collimated jet. We also detect resolved emission further downstream, in the position of the jet knot known as HST-1. In this region, the total flux density is 17.9 mJy and the peak brightness is 2.7 mJy/beam, with the brightest component trailing the downstream emission.

The observations are part of an ongoing monitoring with eVLBI and previous epochs were carried out on 2009 Nov 19 and 2010 Jan 27. The total flux density and peak brightness of the main jet and of HST-1 do not seem to have undergone substantial changes so far. Follow up observations are planned, with a fourth observation epoch already granted.

e-VLBI developments in Europe were supported by the EC DG-INFSO funded Communication Network Developments project 'EXPReS' ( The European VLBI Network ( is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils.

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