Gabriele Giovannini Dipartimento di Astronomia, Bologna University

Gabriele Giovannini

Dipartimento di Astronomia, Bologna UniversityIstituto di Radioastronomia - INAF

EVN observations of M87 as follow-up on a recent TeV flare

In collaboration with M. Giroletti & C. Casadio – IRA-INAF BolognaM. Beilicke & H. Krawczynski Phys. Dept. – Washington, MO A. Cesarini School of Physics, Univ. Of Ireland Galway

1 mas5 mas

Krichbaum

43 GHz86 GHz

M87 – A well known friend• 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

Walker

core

HST-1

500 pc

A VHE у-ray emitting:

2003-2006 by HESS – variability on time scale of days in high statedata (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

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-12008 TeV flare with radio flare of the nucleus

In this scenario we started a program of e-EVN observationsat 5 GHz – large field of view – high sensitivity - high resolution:2009 Nov. 192010 Jan 272010 Feb 10 high flux level at > 100 GeV: MAGIC ATel 24312010 March 62010 March 28 Apr. 9 strong flare VERITAS/MAGIC2010 May 182010 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 degreeWe 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

M873C192

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)

Optical 1995

VLA 1995 15 GHz

3mJy/beam

VLA 15 GHz 2008.928 mJy/beam

Harris et al. 2006

HST-1 First detected in optical (Perlman et al. 1999),

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 3.42010.38 2.8

HST-1 well detected in oure-EVN images

Jan 27 2010

HPBW 8x3.4 mas

VLA: unresolvedVLBI: peak

Chang et al.2010

Cheung et al. 2007

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

•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

THANK YOU