An Exceptional Very High Energy Gamma-Ray Flare of PKS 2155–304

By F. Aharonian, A. Akhperjanian, A. R. Bazer-Bachi, B. Behera, M. Beilicke, W. Benbow, D. Berge, K. Bernlöhr, Catherine Boisson, O. Bolz and 127 more. 2007

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The high-frequency peaked BL Lac PKS 2155-304 at redshift z = 0.116 is a well-known VHE (>100 GeV) γ-ray emitter. Since 2002 its VHE flux has been monitored using the H.E.S.S. stereoscopic array of imaging atmospheric Cerenkov telescopes in Namibia. During the 2006 July dark period, the average VHE flux was measured to be more than 10 times typical values observed from the object. This article focuses solely on an extreme γ-ray outburst detected in the early hours of 2006 July 28 (MJD 53,944). The average flux observed during this outburst is I(>200 GeV) = (1.72 ± 0.05stat ± 0.34syst) × 10-9 cm-2 s-1, corresponding to ~7 times the flux, I(>200 GeV), observed from the Crab Nebula. Peak fluxes are measured with 1 minute timescale resolution at more than twice this average value. Variability is seen up to ~600 s in the Fourier power spectrum, and well-resolved bursts varying on timescales of ~200 s are observed. There are no strong indications for spectral variability within the data. Assuming the emission region has a size comparable to the Schwarzschild radius of a ~109 M☉ black hole, Doppler factors greater than 100 are required to accommodate the observed variability timescales.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/76729767260fffcd9402925874f827ed0aa07f62

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Citations in the corpus

General physical properties of bright Fermi blazars (2009, background): “Another problem, with the standard one–zone SSC scenario, concerns the ultrafast (i.e. minutes) variability sometims seen at high energies (Aharonian et al. 2007, Albert et al. 2007).”
A Monte Carlo template based analysis for air-Cherenkov arrays (2014, background): “The ideal data-set for the point spread function comparison is that taken during the strong flaring activity of the blazar PKS2155−304 [18] in 2006.”
TeV BL Lac objects at the dawn of the Fermi era (2009, background): “The great majority of these BL Lac are known to be extremely variable in the TeV band, showing variations with factors as large as 10 on time-scales as short as hours or even minutes (e.g. Aharonian et al. 2007a; Albert et al. 2007a).”
MINUTE-TIMESCALE >100 MeV γ-RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI-LAT IN 2015 JUNE (2016, background): “These timescales are comparable to the shortest variability timescales detected above 100 GeV in a handful of blazars and a radio galaxy by ground-based Cherenkov telescopes (PKS 2155−304, Aharonian et al. 2007; Mrk 501, Albert et al. 2007; IC 310, Aleksić et al. 2014).”
Black Hole Flares: Ejection of Accreted Magnetic Flux through 3D Plasmoid-mediated Reconnection (2021, background): “Rapid γ-ray flares have been observed from active galactic nuclei, in the form of very-highenergy (>100 GeV) emission (Aharonian et al. 2007; Albert et al. 2007; Aharonian et al. 2009; Aleksić et al. 2014).”
Implications of very rapid TeV variability in blazars (2007, background): “The shortest variability timescales that have been measured to date in PKS 2155–304 (Aharonian et al. 2007) and Mrk 501 (Albert et al. 2007a) are 3–5 minutes, so we set tvar = 300t5 s.”
The power of blazar jets (2007, background): “…et al. 2007a; see C02); 1959+650 (Albertet al. 2006c; see C02); 2005–489 (Aharonian et al. 2005a; see C02 and G02); 2155–304 (Aharonian et al. 2005b; Aharonian et al. 2007b; already present in G98 as an EGRET source); 2200+420 (Albertet al. 2007b; already present in G98 as an EGRET source);…”
Dark matter and fundamental physics with the Cherenkov Telescope Array (2012, background): “similarly at its high level [175], but 120 s duration; the bottom panel is for a 610s”
The blazar sequence: a new perspective (2008, background): “The reasons are the very short variability time-scales observed for the TeV flux (3 min in PKS 2155−304, Aharonian et al. 2007; see the implications in Begelman, Fabian & Rees 2008 and models in Ghisellini & Tavecchio 2008); and the necessity, in single zone SSC models, to account for the large…”
Fast TeV variability in blazars: jets in a jet (2009, background): “On the other hand, when it occurs, it is characterized by several flares on ∼ 1 hour timescales (e.g. Aharonian et al. 2007).”
Rapid variability in TeV blazars: the case of PKS 2155—304 (2008, background): “The mass of the central black hole of PKS 2155–304 is uncertain (of the order of109 M⊙; Aharonian et al. 2007) but even a (prudently small) mass ofM = 108 solar masses corresponds to a light travel time across the Schwarzschild radius of103 s.”