Gabriele Giovannini Dipartimento di Astronomia, Bologna University
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Transcript of Gabriele Giovannini Dipartimento di Astronomia, Bologna University
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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
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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
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core
HST-1
500 pc
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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
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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
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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
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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)
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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),
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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
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VLA: unresolvedVLBI: peak
Chang et al.2010
Cheung et al. 2007
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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
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•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
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THANK YOU