Radio and X-ray variability of the nucleus of Centaurus A /NGC 5128/

Beall, J. H.; Rose, William K.; Graf, W.; Price, K. M.; Dent, W. A.; Hobbs, R. W.; Dennis, B. R.; Crannell, C. J.; Conklin, E. K.; Ulich, B. L.

doi:10.1086/155845

Cited by 33 publications

(43 citation statements)

References 4 publications

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“…The results of these campaigns show both similarities and significant differences in the data from some epochs of galactic microquasars, including GRS 1915+105 (Mirabel, et al, 1998; Rahoui et al, 2008), the concurrent radio and x-ray data (Beall et al, 1978) on Centaurus A (NGC 5128), 3C120 (Marscher (2006), and 3C454.3 as reported by Bonning et al (2009), and Cygnus A (Carilli, et al, 1996), to name a few. The Bonning et al analysis of the 3C454.3 data showed the first results from the Fermi LAT Space Telescope (Abdo 2009a(Abdo , 2009b for the concurrent variability at optical, UV, IR, and γ-ray frequencies for that source.…”

Section: Introductionmentioning

confidence: 74%

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A Review of Astrophysical Jets

Beall¹

2018

Proceedings of XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop — PoS(MULTIF2017)

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This review continues a series that considers our evolving understanding of the nature of astrophysical jets. These have been defined as linear structures on the sky, typically bi-polar, and originating from a common source. Ironically, the original modeling consisted of analytically solveable estimates of radiation processes based on spherical symmetry. We now know that jets are associated with outflows originating from accretion processes in star-forming regions, compact objects (such as neutron stars and black holes), γ-ray bursts associated with stellar collapse, active galactic nuclei, and in some pulsars. In pulsars, the jet production can be drawn from angular momentum loss from the pular. In accreting systems, the jet production seems to be entangled intimately with processes in the accretion disks around the compact objects. The jets can be extremely powerful in terms both of their kinetic luminosity and radiative signatures, and often emit radiation over the entire electromagnetic spectrum, from radio to γ-rays. Astrophysical jets often appear to be one-sided and Doppler boosted. This phenomenon is usually interpreted as evidence of bulk relativistic motion of the emitting particles. In the last three decades and more and as a result of observing campaigns using detectors sensitive from radio to γ-ray energies, theoretical models of these sources have become richer and more complex. As noted above, models have moved from assumptions of isotropy that made analytic calculations possible, to fully anisotropic models of emission from the jets and their interactions with the interstellar and intra-cluster medium. Such anisotropic calculations are only possible because we now have extensive computational resources that can solver the rather complex emission models that result from such anisotropies. In addition, the degree of international cooperation required for observing campaigns of these sorts is remarkable, since the instruments include among others the Very Large Array (VLA), the Very Long Baseline Array (VLBA), the millimeter wave interferometeter network, and entire constellations of satellite instruments, often working in concert. This last point is critically important. The increased resolution of observational systems has taken us from degrees to arcminutes to arcseconds to milliarcseconds, and now to microarcseconds in certain instances. The milliarscecond and microarcsecond observations have shown us the truly dynamic nature of the emitting regions of these remarkable objects. In this paper, I discuss some relevant observations from these efforts and the theoretical interpretations they have occasioned.

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Section: Introductionmentioning

confidence: 74%

“…In fact, Beall et al (1978) have noted that the luninosity of the central source, which is clearly connected to the giant radio lobes via the jets flowing outward from the core of Cen A, could in fact provide the energy of the giant radio lobes.…”

Section: Introductionmentioning

confidence: 99%

A Review of Astrophysical Jets

Beall¹

2018

Proceedings of XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop — PoS(MULTIF2017)

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“…This result is the first report of concurrent radio and X-ray variability of an active galaxy. Mushotzky et al [37], using the weekly 10.7 GHz data obtained by Beall et al [3] demonstrate that the 10.7 GHz radio data track the 2 ÷ 6 keV X-ray data on weekly time scales, also.…”

Section: Introductionmentioning

confidence: 90%

“…First, as Beall et al [3] note, the radio and X-ray light curves track one another. This result is the first report of concurrent radio and X-ray variability of an active galaxy.…”

Section: Introductionmentioning

confidence: 92%

“…The most likely explanation for the changes in the spectrum of the Cen A data at 100 keV [3] is that the emitting region suffered an injection of energetic electrons. That is, a jet-ambient-medium interaction dumped energetic particles into a putative "blob", or, equivalently, that there was a re-acceleration of the emitting electrons on a timescale short compared to the expansion time of the source.…”

Section: A Comment On Particle Acceleration In the Jet-ambient-mediummentioning

confidence: 99%

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From Galactic to Extragalactic Jets: A Review

Beall

2013

Acta Polytech

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Abstract. An analysis of the data that have recently become available from observing campaigns, including VLA, VLBA, and satellite instruments, shows some remarkable similarities and significant differences in the data from some epochs of galactic microquasars, including GRS 1915+105, the concurrent radio and X-ray data [3] on Centaurus A (NGC 5128), 3C120 [35], and 3C454.3 as reported by Bonning et al. [16], which showed the first results from the Fermi Space Telescope for the concurrent variability at optical, UV, IR, and γ-ray variability of that source. In combination with observations from microquasars and quasars from the MOJAVE Collaboration [32], these data provide time-dependent evolutions of radio data at mas (i.e., parsec for AGNs, and Astronomical Unit scales for microquasars). These sources all show a remarkable richness of patterns of variability for astrophysical jets across the entire electromagnetic spectrum. It is likely that these patterns of variability arise from the complex structures through which the jets propagate, but it is also possible that the jets' constitution, initial energy, and collimation have significant observational consequences. On the other hand, Ulrich et al. [42] suggest that this picture is complicated for radio-quiet AGN by the presence of significant emission from accretion disks in those sources. Consistent with the jet-ambient-medium hypothesis, the observed concurrent radio and X-ray variability of Centaurus A [3] could have been caused by the launch of a jet element from Cen A's central source and that jet's interaction with the interstellar medium in the core region of that galaxy.

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