Rapid variability in TeV blazars: the case of PKS 2155—304
By G. Ghisellini, F. Tavecchio. 2008
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Recent Cherenkov observations of BL Lacertae (BL Lac) objects showed that the TeV (teraelectron volt) flux of PKS 2155−304 changed by a factor of 2 in just 3–5 min. This fast variability can be accounted for if the emitting region is moving with a bulk Lorentz factor Γ∼ 50 and a similar relativistic Doppler factor. If this Γ is adopted, several models can fit the data, but, irrespective of the chosen model, the jet is matter dominated. The Doppler factor requires viewing angles of the order of 1° or less: if the entire jet is as narrow as this, then we have problems with current unification schemes. This suggests that there are small active regions, inside a larger jet, moving faster than the rest of the plasma, occasionally pointing at us. Coordinated X-ray/TeV variability can discriminate between the different scenarios.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/704f7410a62f78f58717dbb1f2f596460dfc836b
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Citations in the corpus
- TeV BL Lac objects at the dawn of the Fermi era (2009, background): “Faster variations (such as those observed in PKS 2155−304 and Mkn 501: Aharonian et al. 2007a; Albert et al. 2007a) require modifications of this scheme (Ghisellini & Tavecchio 2008b; Ghisellini et al. 2009b; Giannios, Uzdensky & Begelman 2009; Neronov, Semikoz & Sibiryakov 2008).”
- Reconnection-driven plasmoids in blazars: fast flares on a slow envelope (2012, background): “Fast electron beams (with bulkγe ∼ 106) may develop along magnetic field lines close to the light cylinder (i.e. within severalRSch, see, Ghisellini & Tavecchio 2008).”
- The Fermi blazars' divide (2009, background): “Indeed, for TeV BL Lacs, which span the entire region of BL Lacs, the available estimates indicate high black hole masses (e.g. Wagner 2008, Ghisellini & Tavecchio 2008a), in some cases exceeding109M⊙.”
- The blazar sequence: a new perspective (2008, background): “…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 separation, in frequency, of the two peaks of…”
- MAGIC DISCOVERY OF VERY HIGH ENERGY EMISSION FROM THE FSRQ PKS 1222+21 (2011, background): “…to invoke the presence of very compact emission regions embedded within the large scale jet, as already proposed by several authors to explain the exceptionally rapid variability in PKS 2155-304, Mkn 501 and AO 0235+164 (Ghisellini & Tavecchio 2008; Giannios et al. 2009; Marscher & Jorstad 2010).”
- Fast TeV variability in blazars: jets in a jet (2009, methodology): “Inferring the magnetization of the jet by modeling the TeV flares (as done e.g. by Ghisellini & Tavecchio 2008) may be misleading in the context of the model presented here.”
- Synchrotron Self-Compton Analysis of TeV X-Ray-Selected BL Lacertae Objects (2008, methodology): “The jet powers of our fits are significantly larger than the jet power, 6 × 1043 ergs s−1, found for the SSC fit to the same PKS 2155–304 data by Ghisellini & Tavecchio (2008).”
- General physical properties of bright Fermi blazars (2009, background): “There is, in our opinion (Ghisellini & Tavecchio 2008), another important parameter, besides the jet power, controlling the look of the emitted SED and its bolometric luminosity: the mass of the black hole.”