MODELING THE HARD TeV SPECTRA OF BLAZARS 1ES 0229+200 AND 3C 66A WITH AN INTERNAL ABSORPTION SCENARIO

Zacharopoulou, Olga; Khangulyan, D.; Aharonian, F.; Costamante, L.

doi:10.1088/0004-637x/738/2/157

Cited by 32 publications

(37 citation statements)

References 33 publications

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“…Stecker et al 2007), in the case of internal photon absorption (Aharonian et al 2008b), or in proton-synchrotron models (e.g. Aharonian 2000;Zacharopoulou et al 2011). For the latter criterion, the expected cascade emission is investigated and, additionally, the total intrinsic luminosity is compared to the Eddington luminosity of the AGN.…”

Section: Discussionmentioning

confidence: 99%

Limits on the extragalactic background light in theFermiera

Meyer

Raue

Mazin

et al. 2012

A&A

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Very high energy (VHE, energy E < ∼ 100 GeV) γ-rays from cosmological sources are attenuated due to the interaction with photons of the extragalactic background light (EBL) in the ultraviolet to infrared wavelength band. The EBL, thus, leaves an imprint on the observed energy spectra of these objects. In the last four years, the number of extragalactic VHE sources discovered with imaging atmospheric Cherenkov telescopes (IACTs), such as MAGIC, H.E.S.S., and VERITAS, has doubled. Furthermore, the measurements of the Fermi satellite brought new insights into the intrinsic spectra of the sources at GeV energies. In this paper, upper limits on the EBL intensity are derived by considering the most extensive VHE source sample ever used in this context. This is accomplished by constructing a large number of generic EBL shapes and combining spectral informations from Fermi and IACTs together with minimal assumptions about the source physics at high and very high γ-ray energies. The evolution of the EBL with redshift is accounted for and the possibility of the formation of an electromagnetic cascade and the implications on the upper limits are explored. The EBL density at z = 0 is constrained over a broad wavelength range between 0.4 and 100 μm. At optical wavelengths, the EBL density is constrained below 24 nW m −2 sr −1 and below 5 nW m −2 sr −1 between 8 μm and 31 μm.

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Section: Discussionmentioning

confidence: 99%

Limits on the extragalactic background light in theFermiera

Meyer

Raue

Mazin

et al. 2012

A&A

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“…Moreover, in the case of blazars with extremely hard TeV source spectra (i.e. after correction for the intergalactic absorption), the energy-dependent absorption can be a natural explanation of the unusually hard gamma-ray spectra (Aharonian et al 2008;Zacharopoulou et al 2011). …”

Section: Proton Synchrotron Radiationmentioning

confidence: 99%

RAPID TeV VARIABILITY IN BLAZARS AS A RESULT OF JET-STAR INTERACTION

Barkov

Aharonian

Bogovalov

et al. 2012

ApJ

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115

173

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We propose a new model for the description of ultra-short flares from TeV blazars by compact magnetized condensations (blobs), produced when red giant stars cross the jet close to the central black hole. Our study includes a simple dynamical model for the evolution of the envelope lost by the star in the jet, and its high energy nonthermal emission through different leptonic and hadronic radiation mechanisms. We show that the fragmented envelope of the star can be accelerated to Lorentz factors up to 100 and radiate effectively the available energy in gamma-rays predominantly through proton synchrotron radiation or external inverse Compton scattering of electrons. The model can readily explain the minute-scale TeV flares on top of longer (typical time-scales of days) gamma-ray variability as observed from the blazar PKS 2155−304. In the framework of the proposed scenario, the key parameters of the source are robustly constrained. In the case of proton synchrotron origin of the emission a mass of the central black hole of M BH ≈ 10 8 M ⊙ , a total jet power of L j ≈ 2 × 10 47 erg s

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“…Hard intrinsic spectra in the γ-ray range can also arise in hadronic models (Rachen & Meszaros 1998;Aharonian 2000;Mücke & Protheore 2001;Reimer et al 2004;Zacharopoulou et al 2011). Variability times as short as ∼10 4 s can originate from the synchrotron cooling time of protons in strong ∼100 G magnetic fields, if the observed γ-ray emission has proton and/or muon synchrotron origin.…”

Section: Hadronic Modelsmentioning

confidence: 99%

Very hard gamma-ray emission from a flare of Mrk 501

Neronov

Semikoz

Taylor

2012

A&A

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Aims. We investigate the peculiar properties of a large TeV γ-ray flare from Mrk 501 detected during the 2009 multiwavelength campaign. Methods. We identified the counterpart of the flare in the Fermi/LAT telescope data and studied its spectral and timing characteristics. Results. A strong order-of-magnitude increase of the very-high-energy γ-ray flux during the flare was not accompanied by an increase in the X-ray flux, so that the flare was one of the "orphan"-type TeV flares observed in BL Lacs. The flare lasted about one month at energies above 10 GeV. The flaring source spectrum in the 10-200 GeV range was very hard, with a photon index Γ = 1.1 ± 0.2, harder than that observed in any other blazar in the γ-ray band. No simultaneous flaring activity was detected below 10 GeV. Different variability properties of the emission below and above 10 GeV indicate the existence of two separate components in the spectrum. We investigate possible explanations of the very hard flaring component. We consider, among others, the possibility that the flare is produced by an electromagnetic cascade initiated by very-high-energy γ-rays in the intergalactic medium. Within such an interpretation, peculiar spectral and temporal characteristics of the flare could be explained if the magnetic field in the intergalactic medium is on the order of 10 −17 −10 −16 G.

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MODELING THE HARD TeV SPECTRA OF BLAZARS 1ES 0229+200 AND 3C 66A WITH AN INTERNAL ABSORPTION SCENARIO

Cited by 32 publications

References 33 publications

Limits on the extragalactic background light in theFermiera

Limits on the extragalactic background light in theFermiera

RAPID TeV VARIABILITY IN BLAZARS AS A RESULT OF JET-STAR INTERACTION

Very hard gamma-ray emission from a flare of Mrk 501

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