Gabriele Giovannini Dipartimento di Astronomia, Bologna University

1. EVN observations of M87 as follow-up on a recent TeV flare Gabriele Giovannini Dipartimento di Astronomia, Bologna University Istituto di Radioastronomia - INAF 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

2. Good resolution Nearby: 16.7 Mpc Large black hole mass: ~6X109 Msun Scale 1 mas = 0.081pc = 140 Rs. Well studied at all wavelengths from radio to TEV M87 – A well known friend Krichbaum Walker 86 GHz 43 GHz 5 mas 1 mas

3. core 500 pc HST-1

4. A VHE у-ray emitting: 2003-2006 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 50 2001-2006 with a major flare on 2005 Harris et al. 2009 Superluminal motions of radio features in HST-1 (Cheung et al. 2007)

5. 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-1 • 2008 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: • Nov. 19 • Jan 27 • 2010 Feb 10 high flux level at > 100 GeV: MAGIC ATel 2431 • 2010 March 6 • 2010 March 28 • Apr. 9 strong flare VERITAS/MAGIC • 2010 May 18 • 2010 June 9 not yet reduced

6. 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) : 20o – 30o Core dominance: core radio power lower than expected from the unbeamed total radio power 3C192 M87

7. core flux density at 5 GHz from our eEVN data (HPBW 8x3.4 mas): November 19 - 2009 1.81 Jy ± 0.03 January 27 - 2010 1.81 February 10 - 2010 1.80  VHE activity March 6 - 2010 1.89 March 28 - 2010 2.01  VHE activity Apr. 9th May 18 - 2010 1.93 waiting 1 more epoch (June 9)

8. HST-1 First detected in optical (Perlman et al. 1999), Optical 1995 VLA 1995 15 GHz Harris et al. 2006 3mJy/beam 28 mJy/beam VLA 15 GHz 2008.9

9. Jan 27 2010 HST-1 well detected in our e-EVN images HPBW 8x3.4 mas Peak flux density: 2009.87 3.5 mJy/beam 2010.07 2.7 Total flux density ~ < 27 > mJy 2010.11 3.0 Total VLA at 8.4 GHz: 45 mJy 2010.17 4.6 in 2008.9 2010.25 3.4 2010.38 2.8

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

11. CONCLUSIONSfrom 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 <1805 mJy> 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

12. From inhomogeneous VLBI data (different angular resolution, frequency • and network) the HST-1 brightest feature was moving at 0.5 – 0.6 c • before 2005.5 and at 2.7 c after 2005.5 • A collective HST-1 proper motion is confirmed by high resolution • VLA data from 2003. 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 150-170 pc (deprojected) • from the core • A more regular and longer multifrequency comparison is necessary • to understand nuclear and HST-1 propertiers in M87

13. THANK YOU