Article

# Radio Imaging of the Very-High-Energy γ-Ray Emission Region in the Central Engine of a Radio Galaxy

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Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645, USA.
(Impact Factor: 31.48). 08/2009; 325(5939):444-8. DOI: 10.1126/science.1175406
Source: PubMed

ABSTRACT The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.

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Available from: I. Oya, Jul 26, 2014
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• "Variability is also seen in objects where jets are not closely aligned with the line-of-sight to the observer, with the day-timescale TeV variability of M 87 (Aharonian et al. 2006) as the best studied case. Simultaneous VLBI and TeV observations of M 87 indicate a strong increase in flux from the nucleus during VHE flares (Acciari et al. 2009), suggesting particle acceleration is taking place very close to the central supermassive black hole. "
##### Article: High-energy emission from transients
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ABSTRACT: Cosmic explosions dissipate energy into their surroundings on a very wide range of time scales: producing shock waves and associated particle acceleration. The historical culprits for the acceleration of the bulk of Galactic cosmic rays are supernova remnants: explosions on approximately 10(4) year time scales. Increasingly, however, time-variable emission points to rapid and efficient particle acceleration in a range of different astrophysical systems. Gamma-ray bursts have the shortest time scales, with inferred bulk Lorentz factors of approximately 1000 and photons emitted beyond 100 GeV, but active galaxies, pulsar wind nebulae and colliding stellar winds are all now associated with time-variable emission at approximately teraelectron volt energies. Cosmic photons and neutrinos at these energies offer a powerful probe of the underlying physical mechanisms of cosmic explosions, and a tool for exploring fundamental physics with these systems. Here, we discuss the motivations for high-energy observations of transients, the current experimental situation, and the prospects for the next decade, with particular reference to the major next-generation high-energy observatory, the Cherenkov Telescope Array.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 06/2013; 371(1992):20120279. DOI:10.1098/rsta.2012.0279 · 2.86 Impact Factor
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• "Theories involving particle acceleration in the jet usually place the emission region between 30 and a few thousand R Sch from the black hole, with R Sch the Schwarzschild radius (R Sch = 3×10 14 cm for a 10 9 M ¤ black hole). The observations of exceptionally strong γ-ray flares from M87 in 2008 observed by H.E.S.S., MAGIC and VERITAS in temporal coincidence with an exceptionally strong VLBA radio flare from the M87 radio core were interpreted as evidence for an origin of the γray flares within a projected distance of 50 R Sch from the central engine [31]. Unfortunately, a similar γ-flare in 2011 was not accompanied by a comparable radio flare and did not corroborate the association. "
##### Article: Science Drivers for AGN Observations with the Cherenkov Telescope Array
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ABSTRACT: The current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs), including the H.E.S.S., MAGIC, and VERITAS telescope arrays, have made substantial contributions to our knowledge about the structure and composition of the highly relativistic jets from Active Galactic Nuclei (AGNs). In this paper, we discuss some of the outstanding scientific questions and give a qualitative overview of AGN related science topics which will be explored with the next-generation Cherenkov Telescope Array (CTA). CTA is expected to further constrain the structure and make-up of jets, and thus, to constrain models of jet formation, acceleration, and collimation. Furthermore, being the brightest well-established extragalactic sources of TeV {\gamma}- rays, AGNs can be used to probe the EBL, intergalactic magnetic fields, and the validity of the Lorentz Invariance principle at high photon energies.
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• "– 4 – M87 Cen A black hole mass m = M/M ⊙ (3.2 ± 0.9) · 10 9 (1) , (6.4 ± 0.5) · 10 9 (2) (4.5 +1.7 −1.0 ) · 10 7 , (5.5 ± 3.0) · 10 7 (3) Gravitational radius R G 4.72 · 10 14 cm= 1.53 · 10 −4 pc ( * ) , 7.375 · 10 12 cm = 2.390 · 10 −6 pc 9.44 · 10 14 cm= 3.06 · 10 −4 pc ( * * ) distance from Earth d (16.7 ± 0.2) Mpc (4) (3.8 ± 0.1) Mpc (5) inclination i ( 15 − 25) • (6) , ( 30 − 35) • (7) , ( 15 − 80) • (9) , ( 30 − 45) • (8) ( 50 − 80) • (10) (pc-scale) nuclear X-ray luminosity L X 7.0 · 10 40 erg·s −1 ((0.5 − 7)keV) (11) ∼ 5·10 41 erg·s −1 ((2−10)keV) (12) nuclear bolometric ∼ 10 42 erg s −1 (13) ∼ 10 43 erg s −1 (14) luminosity L bol ( * ) for m = 3.2 · 10 9 , ( * * ) for m = 6.4 · 10 9 , (1) Macchetto et al. (1997), (2) Gebhardt and Thomas (2009), (3) Neumayer et al. (2010), (4) Mei et al. (2007), (5) Harris et al. (2009) , (6) Acciari et al. (2009),(7) Bicknell and Begelman (1996), (8) Ly et al. (2007), (9) Aharonian et al. (2009) and references therein, (10)Tingay et al. (1998), (11) Di Matteo et al. (2003), (12)Evans et al. (2004), (13) Reynolds et al. (1996) , (14) Karovska et al. (2002) "
##### Article: Internal gammagamma Opacity in Active Galactic Nuclei and the Consequences for the TeV Observations of M87 and Cen A
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