Characterizing the γ-ray long-term variability of PKS 2155−304   with H.E.S.S. and Fermi-LAT

H. Abdalla; P. Aubert; Jérome Chevalier; A. Fiasson; F. Krayzel; G. Lamanna; J.P. Lees; G. Maurin; Q. Piel; S. Rosier-Lees; D.A. Sanchez; T. Vuillaume; J. Bolmont; M. Cerruti; R. Chalme-Calvet; M. Chétien; A. Jacholkowska; D. Kerszberg; Michel Kieffer; J.-P. Lenain; C. Perennes; M. Settimo; J.-P. Tavernet; P. Vincent; J. Bregeon; R.C.G. Chaves; J. Devin; Y.A. Gallant; A. Marcowith; M. Padovani; M. Renaud; G. Vasileiadis; J. Carr; J.-P. Ernenwein; J. Niemiec; C. Trichard; F. Brun; B. Condon; M.-H. Grondin; H. Laffon; M. Lemoine-Goumard; B. Degrange; S. Fegan; G. Fontaine; B. Giebels; M. Holler; C. Mariaud; M. De Naurois; D. Zaborov; F. Zefi; A. Djannati-Ataï; S. Gabici; L. Jouvin; B. Khélifi; A. Lemière; S. Pita; M. Punch; T. Tavernier; R. Terrier; Maialen Arrieta; Catherine Boisson; Olivier Hervet; Lefaucheur J.; C. Rulten; Helene Sol; Andreas Zech

doi:10.1051/0004-6361/201629419

Journal articles

Characterizing the γ-ray long-term variability of PKS 2155−304 with H.E.S.S. and Fermi-LAT

H. Abdalla P. Aubert ¹ Jérome Chevalier ¹ A. Fiasson ¹ F. Krayzel ¹ G. Lamanna ¹ J.P. Lees ¹ G. Maurin ¹ Q. Piel ¹ S. Rosier-Lees ¹ D.A. Sanchez ¹ T. Vuillaume ¹ J. Bolmont ² M. Cerruti ² R. Chalme-Calvet ² M. Chétien ² A. Jacholkowska ² D. Kerszberg ² Michel Kieffer ² J.-P. Lenain ² C. Perennes ² M. Settimo ² J.-P. Tavernet ² P. Vincent ² J. Bregeon ³ R.C.G. Chaves ³ J. Devin ³ Y.A. Gallant ³ A. Marcowith ³ M. Padovani ³ M. Renaud ³ G. Vasileiadis ³ J. Carr ⁴ J.-P. Ernenwein ⁴ J. Niemiec ⁴ C. Trichard ⁴ F. Brun ⁵ B. Condon ⁵ M.-H. Grondin ⁵ H. Laffon ⁵ M. Lemoine-Goumard ⁵ B. Degrange ⁶ S. Fegan ⁶ G. Fontaine ⁶ B. Giebels ⁶ M. Holler ⁶ C. Mariaud ⁶ M. De Naurois ⁶ D. Zaborov ⁶ F. Zefi ⁶ A. Djannati-Ataï ⁷ S. Gabici ⁷ L. Jouvin ⁷ B. Khélifi ⁷ A. Lemière ⁷ S. Pita ⁷ M. Punch ⁷ T. Tavernier ⁷ R. Terrier ⁷ Maialen Arrieta ⁸ Catherine Boisson ⁸ Olivier Hervet ⁸ Lefaucheur J. ⁸ C. Rulten ⁸ Helene Sol ⁸ Andreas Zech ⁸

1 LAPP - Laboratoire d'Annecy de Physique des Particules

2 LPNHE (UMR_7585) - Laboratoire de Physique Nucléaire et de Hautes Énergies

3 LUPM - Laboratoire Univers et Particules de Montpellier

4 CPPM - Centre de Physique des Particules de Marseille

5 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan

6 LLR - Laboratoire Leprince-Ringuet

7 APC (UMR_7164) - AstroParticule et Cosmologie

8 LUTH (UMR_8102) - Laboratoire Univers et Théories

Abstract : Studying the temporal variability of BL Lac objects at the highest energies provides unique insights into the extreme physical processes occurring in relativistic jets and in the vicinity of super-massive black holes. To this end, the long-term variability of the BL Lac object PKS 2155−304 is analyzed in the high (HE, 100 MeV < E < 300 GeV) and very high energy (VHE, E > 200 GeV) γ-ray domain. Over the course of ~9 yr of H.E.S.S. observations the VHE light curve in the quiescent state is consistent with a log-normal behavior. The VHE variability in this state is well described by flicker noise (power-spectral-density index βVHE = 1.10+0.10-0.13) on timescales larger than one day. An analysis of ~5.5 yr of HE Fermi-LAT data gives consistent results (βHE = 1.20+0.21-0.23, on timescales larger than 10 days) compatible with the VHE findings. The HE and VHE power spectral densities show a scale invariance across the probed time ranges. A direct linear correlation between the VHE and HE fluxes could neither be excluded nor firmly established. These long-term-variability properties are discussed and compared to the red noise behavior (β ~ 2) seen on shorter timescales during VHE-flaring states. The difference in power spectral noise behavior at VHE energies during quiescent and flaring states provides evidence that these states are influenced by different physical processes, while the compatibility of the HE and VHE long-term results is suggestive of a common physical link as it might be introduced by an underlying jet-disk connection.

Keywords : galaxies: active BL Lacertae objects: individual: PKS 2155-304 gamma rays: galaxies galaxies: jets galaxies: nuclei radiation mechanisms: non-thermal

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Journal articles

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Physics [physics] / Astrophysics [astro-ph]

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Characterizing the γ-ray long-term variability of PKS 2155−304 with H.E.S.S. and Fermi-LAT

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Characterizing the γ-ray long-term variability of PKS 2155−304 with H.E.S.S. and Fermi-LAT

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