Very High Energy Gamma Rays from PKS 2155−304

Chadwick, P. M.; Lyons, K.; McComb, T. J. L.; Orford, K. J.; Osborne, J. L.; Rayner, S. M.; Shaw, S. E.; Turver, K. E.; Wieczorek, G.

doi:10.1086/306862

Cited by 166 publications

(124 citation statements)

References 29 publications

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“…10-12, 20 2000, 30, Jun. 1-5 1ES 1959+650 (Nishiyama et al 1999), and PKS 2155-304 (Chadwick et al 1999). Most recently, statistically significant TeV signals have been reported also for H 1426+428, by the VERITAS (Horan & the VERITAS coll.…”

Section: Introductionmentioning

confidence: 96%

TeV gamma rays from the blazar H 1426+428 and the diffuse extragalactic background radiation

Aharonian

Akhperjanian

Barrio

et al. 2002

A&A

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Abstract. The detection of TeV γ-rays from the blazar H 1426+428 at an integral flux level of (4 ± 2stat ± 1syst) × 10 −12 erg cm −2 s −1 above 1 TeV with the HEGRA imaging atmospheric Cherenkov telescope system is reported. H 1426+428 is located at a redshift of z = 0.129, which makes it the most distant source detected in TeV γ-rays so far. The TeV radiation is expected to be strongly absorbed by the diffuse extragalactic background radiation (DEBRA). The observed energy spectrum of TeV photons is in good agreement with an intrinsic power law spectrum of the source ∝ E −1.9 corrected for DEBRA absorption. Statistical errors as well as uncertainties about the intrinsic source spectrum, however, do not permit strong statements about the density of the DEBRA infrared photon field.

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Section: Introductionmentioning

confidence: 96%

TeV gamma rays from the blazar H 1426+428 and the diffuse extragalactic background radiation

Aharonian

Akhperjanian

Barrio

et al. 2002

A&A

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“…The high-frequency-peaked BL Lac object (HBL) PKS 2155−304, located at redshift z = 0.117, initially discovered as a VHE γ-ray emitter by the Mark 6 telescope (Chadwick et al 1999), has been detected by the first HESS telescope in 2002−2003(Aharonian et al 2005b. It has been frequently observed by the full array of four telescopes since 2004, either sparsely during the HESS monitoring program or intensely during dedicated campaigns, such as described in Aharonian et al (2005c), showing mean flux levels of ∼20% of the Crab Nebula flux for energies above 200 GeV.…”

Section: Introductionmentioning

confidence: 99%

VHEγ-ray emission of PKS 2155–304: spectral and temporal variability

Abramowski¹,

Acero²,

Aharonian³

et al. 2010

A&A

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Context. Observations of very high-energy γ-rays from blazars provide information about acceleration mechanisms occurring in their innermost regions. Studies of variability in these objects lead to a better understanding of the mechanisms in play. Aims. To investigate the spectral and temporal variability of VHE (>100 GeV) γ-rays of the well-known high-frequency-peaked BL Lac object PKS 2155−304 with the HESS imaging atmospheric Cherenkov telescopes over a wide range of flux states. Methods. Data collected from 2005 to 2007 were analyzed. Spectra were derived on time scales ranging from 3 years to 4 min. Light curve variability was studied through doubling timescales and structure functions and compared with red noise process simulations. Results. The source was found to be in a low state from 2005 to 2007, except for a set of exceptional flares that occurred in July 2006. The quiescent state of the source is characterized by an associated mean flux level of (4.32 ± 0.09 stat ± 0.86 syst ) × 10 −11 cm −2 s −1 above 200 GeV, or approximately 15% of the Crab Nebula, and a power-law photon index of Γ = 3.53 ± 0.06 stat ± 0.10 syst . During the flares of July 2006, doubling timescales of ∼2 min are found. The spectral index variation is examined over two orders of magnitude in flux, yielding different behavior at low and high fluxes, which is a new phenomenon in VHE γ-ray emitting blazars. The variability amplitude characterized by the fractional rms F var is strongly energy-dependent and is ∝E 0.19±0.01 . The light curve rms correlates with the flux. This is the signature of a multiplicative process that can be accounted for as a red noise with a Fourier index of ∼2. Conclusions. This unique data set shows evidence of a low-level γ-ray emission state from PKS 2155−304 that possibly has a different origin than the outbursts. The discovery of the light curve lognormal behavior might be an indicator of the origin of aperiodic variability in blazars.

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“…They have been observed at all wavelengths, from radio through very high energy (VHE) -rays. Six blazars (Mrk 421: Punch et al 1992;Mrk 501: Quinn et al 1996; PKS 2155À314: Chadwick et al 1999;1ES 2344+514: Catanese et al 19971H 1426+428: Horan et al 20021ES 1959+650: Kajino et al 1999Holder et al 2003) have now been detected in VHE -rays (>350 GeV) by ground-based air Cerenkov telescopes. Blazars exhibit variability at all wavelengths on various timescales.…”

Section: Introductionmentioning

confidence: 99%

A Hadronic Synchrotron Mirror Model for the “Orphan” TeV Flare in 1ES 1959+650

Böttcher

2005

ApJ

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Very high energy -ray flares of TeV blazars are generally accompanied by simultaneous flaring activity in X-rays. The recent observations by the Whipple collaboration of an ''orphan'' TeV flare of 1ES 1959+650 (without a simultaneous X-ray flare) are very difficult to reconcile with the standard leptonic synchrotron self-Compton model, which is routinely very successfully employed to explain the spectral energy distribution and spectral variability of TeV blazars. In this paper an alternative scenario is suggested in which the orphan TeV flare may originate from relativistic protons, interacting with an external photon field supplied by electron synchrotron radiation reflected off a dilute reflector. While the external photons will be virtually ''invisible'' to the comoving ultrarelativistic electrons in the jet because of Klein-Nishina effects, their Doppler-boosted energy is high enough to excite a Á-resonance from relativistic protons with Lorentz factors of p $ 10 3 10 4 . This model is capable of explaining the orphan TeV flare of 1ES 1959+650 with plausible parameters, thus constraining the number and characteristic energy of relativistic protons in the jet of this blazar.

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Very High Energy Gamma Rays from PKS 2155−304

Cited by 166 publications

References 29 publications

TeV gamma rays from the blazar H 1426+428 and the diffuse extragalactic background radiation

TeV gamma rays from the blazar H 1426+428 and the diffuse extragalactic background radiation

VHEγ-ray emission of PKS 2155–304: spectral and temporal variability

A Hadronic Synchrotron Mirror Model for the “Orphan” TeV Flare in 1ES 1959+650

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