Gabriele Giovannini Dipartimento di Astronomia, Bologna University Istituto di Radioastronomia - INAF EVN observations of M87 as follow-up on a recent TeV flare In collaboration with M. Giroletti & C. Casadio – IRA-INAF Bologna M. Beilicke & H. Krawczynski Phys. Dept. – Washington, MO A. Cesarini School of Physics, Univ. Of Ireland Galway

1 mas 5 mas Krichbaum 43 GHz 86 GHz M87 – A well known friend Good resolution –Nearby: 16.7 Mpc –Large black hole mass: ~6X10 9 M sun –Scale 1 mas = 0.081pc = 140 Rs. Well studied at all wavelengths from radio to TEV Walker

core HST pc

A VHE у-ray emitting: by HESS – variability on time scale of days in high state data (Aharonian et al. 2006)  promising possibility of TeV production it is the nucleus However HST-1: in the X-ray increased by more than a factor with a major flare on 2005 Superluminal motions of radio features in HST-1 (Cheung et al. 2007) Harris et al. 2009

in February 2008 M87 showed a strong VHE у-ray activity: multiple flares, short term variability. HST-1 was in a low state (in X-ray) Nucleus in its highest state since 2000 (Acciari et al. 2009) 2005 TeV flare with radio flare of HST TeV flare with radio flare of the nucleus In this scenario we started a program of e-EVN observations at 5 GHz – large field of view – high sensitivity - high resolution: 2009 Nov Jan Feb 10 high flux level at > 100 GeV: MAGIC ATel March March 28 Apr. 9 strong flare VERITAS/MAGIC 2010 May June 9 not yet reduced

Results for the core/inner jet region: No visible proper motion from our eEVN data Orientation: literature data: Acciari et al. 2009: 15 – 25 degree We estimate from j/cj brightness and assuming limb-brightened as due to a velocity structure (different Doppler factor) : 20 o – 30 o Core dominance: core radio power lower than expected from the unbeamed total radio power M87 3C192

core flux density at 5 GHz from our eEVN data (HPBW 8x3.4 mas): November Jy ± 0.03 January February  VHE activity March March  VHE activity Apr. 9th May waiting 1 more epoch (June 9)

Optical 1995 VLA GHz 3mJy/beam VLA 15 GHz mJy/beam Harris et al HST-1 First detected in optical (Perlman et al. 1999),

Peak flux density: mJy/beam Total flux density ~ mJy Total VLA at 8.4 GHz: 45 mJy in HST-1 well detected in our e-EVN images Jan HPBW 8x3.4 mas

VLA: unresolved VLBI: peak Chang et al.2010 Cheung et al. 2007

CONCLUSIONS from new e-EVN and literature data Despite of activity and brightness of M87 nuclear region, the radio core dominance is low in comparison with 3CR and B2 radio galaxies The radio core flux density at 5 GHz (HPBW 8x3.4 mas) is constant November 2009– February 2010, after (March) is increasing: 2013 mJy on March 28, and 1.93 on May 18th The HST-1 structure in eEVN images is well resolved in many substructures, variable in time, in morphology and flux density in agreement with previous VLBA images

From inhomogeneous VLBI data (different angular resolution, frequency and network) the HST-1 brightest feature was moving at 0.5 – 0.6 c before and at 2.7 c after A collective HST-1 proper motion is confirmed by high resolution VLA data from The HST-1 kinematic is complex The HST-1 apparent velocity 2.7c implies an intrinsic velocity = 0.94c with an orientation angle of 20 degree. This velocity is in agreement with general FR I jet properties at about pc (deprojected) from the core A more regular and longer multifrequency comparison is necessary to understand nuclear and HST-1 propertiers in M87

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