H.E.S.S. Monitoring of PKS 2155-304 in 2015 and 2016

Wierzcholska, A.; Zacharias, M.; Jankowsky, F.; Wagner, S. J.

doi:10.3390/galaxies7010021

Cited by 7 publications

(4 citation statements)

References 41 publications

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“…Among the TeV sources, about 40% are AGN and more than 20% are high frequency peaked BL Lac type objects (HBLs) [2]. Blazars are extremely variable objects across a wide range of wavelengths, on time scales from minutes (e.g., PKS 2155-304 [3], Mrk 501 ( [4]) to years [5]. Their spectral energy distribution spans from radio to TeV energies and shows a double-peak structure [6].…”

Section: Active Galactic Nucleimentioning

confidence: 99%

Unbiased Long-Term Monitoring at TeV Energies

et al. 2019

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For the understanding of the variable, transient and non-thermal universe, unbiased long-term monitoring is crucial. To constrain the emission mechanisms at the highest energies, it is important to characterize the very high energy emission and its correlation with observations at other wavelengths. At very high energies, only a limited number of instruments is available. This article reviews the current status of monitoring of the extra-galactic sky at TeV energies.

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Section: Active Galactic Nucleimentioning

confidence: 99%

Unbiased Long-Term Monitoring at TeV Energies

et al. 2019

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“…1]; orphan optical flare [e.g. [2][3][4][5]; orphan GeV flare [e.g. [5][6][7][8][9][10]; orphan TeV flare [e.g.…”

Section: Introductionmentioning

confidence: 99%

A unified model for orphan and multi-wavelength blazar flares

Wang¹,

Liu²,

Πετροπούλου³

et al. 2021

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)

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Blazars are a class of active galactic nuclei which host relativistic jets oriented close to the observer's line of sight. Blazars have very complex variability properties. Flares, namely flux variations around the mean value with a well-defined shape and duration, are one of the identifying properties of the blazar phenomenon. Blazars are known to exhibit multi-wavelength flares, but also "orphan" flares, namely flux changes that appear only in a specific energy range. Various models, sometimes at odds with each other, have been proposed to explain specific flares even for a single source, and cannot be synthesized into a coherent picture. In this paper, we propose a unified model for explaining orphan and multi-wavelength flares from blazars in a common framework. We assume that the blazar emission during a flare consists of two components: (i) a quasi-stable component that arises from the superposition of numerous but comparatively weak dissipation zones along the jet, forming the background (low-state) emission of the blazar, and (ii) a transient component, which is responsible for the sudden enhancement of the blazar flux, forming at a random distance along the jet by a strong energy dissipation event. Whether a multiwavelength or orphan flare is emitted depends on the distance from the base of the jet where the dissipation occurs. Generally speaking, if the dissipation occurs at a small/large distance from the supermassive black hole, the inverse Compton/synchrotron radiation dominates and an orphan -ray/optical flare tends to appear. On the other hand, we may expect a multi-wavelength flare if the dissipation occurs at a intermediate distance. We show that the model can successfully describe the spectral energy distribution of different flares from the flat spectrum radio quasar 3C 279 and the BL Lac object PKS 2155-304.

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“…29]; orphan optical flare [e.g. [30][31][32][33]; orphan GeV flare [e.g. [33][34][35][36][37][38]; orphan TeV flare [e.g.…”

Section: Introductionmentioning

confidence: 99%

A unified model for orphan and multi-wavelength blazar flares

Wang,

Liu,

Petropoulou

et al. 2021

Preprint

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Blazars are a class of active galactic nuclei which host relativistic jets oriented close to the observer's line of sight. Blazars have very complex variability properties. Flares, namely flux variations around the mean value with a well-defined shape and duration, are one of the identifying properties of the blazar phenomenon. Blazars are known to exhibit multi-wavelength flares, but also "orphan" flares, namely flux changes that appear only in a specific energy range. Various models, sometimes at odds with each other, have been proposed to explain specific flares even for a single source, and cannot be synthesized into a coherent picture. In this paper, we propose a unified model for explaining orphan and multi-wavelength flares from blazars in a common framework. We assume that the blazar emission during a flare consists of two components: (i) a quasi-stable component that arises from the superposition of numerous but comparatively weak dissipation zones along the jet, forming the background (low-state) emission of the blazar, and (ii) a transient component, which is responsible for the sudden enhancement of the blazar flux, forming at a random distance along the jet by a strong energy dissipation event. Whether a multi-wavelength or orphan flare is emitted depends on the distance from the base of the jet where the dissipation occurs. Generally speaking, if the dissipation occurs at a small/large distance from the supermassive black hole, the inverse Compton/synchrotron radiation dominates and an orphan γ-ray/optical flare tends to appear. On the other hand, we may expect a multi-wavelength flare if the dissipation occurs at an intermediate distance. We show that the model can successfully describe the spectral energy distribution of different flares from the flat spectrum radio quasar 3C 279 and the BL Lac object PKS 2155-304. R0 (10 16 cm) 0.91 +0.07 −0.08 c 3.41 +0.88 −0.54 d B0 (G) 0.45 +0.03 −0.04 0.14 +0.02 −0.01 γmin (10 2 ) 5.07 +0.05 −0.06

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H.E.S.S. Monitoring of PKS 2155-304 in 2015 and 2016

Cited by 7 publications

References 41 publications

Unbiased Long-Term Monitoring at TeV Energies

Unbiased Long-Term Monitoring at TeV Energies

A unified model for orphan and multi-wavelength blazar flares

A unified model for orphan and multi-wavelength blazar flares

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