Characterizing the gamma-ray long-term variability of PKS2155 304 with HESS and Fermi-LAT

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dc.citation.doi10.1051/0004-6361/201629419en_ZA
dc.contributor.authorChen, A.
dc.contributor.authorColafrancesco, S.
dc.contributor.authorJingo, M.
dc.contributor.authorCollaboration, H.E.S.S.
dc.contributor.authorAbdalla, H.
dc.contributor.authorAbramowski, A.
dc.contributor.authorAharonian, F.
dc.contributor.authorAit Benkhali, F.
dc.contributor.authorAkhperjanian, A.G.
dc.contributor.authorAndersson, T.
dc.contributor.authorAngüner, E.O.
dc.contributor.authorArrieta, M.
dc.contributor.authorAubert, P.
dc.contributor.authorBackes, M.
dc.contributor.authorBalzer, A.
dc.contributor.authorBarnard, M.
dc.contributor.authorBecherini, Y.
dc.contributor.authorBecker Tjus, J.
dc.contributor.authorBerge, D.
dc.contributor.authorBernhard, S.
dc.contributor.authorKomin, Nu.
dc.date.accessioned2018-02-06T15:00:24Z
dc.date.available2018-02-06T15:00:24Z
dc.date.issued2017-02
dc.description.abstractStudying 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 = 1.10-0.13 +0.10) on timescales larger than one day. An analysis of ∼5.5 yr of HE Fermi-LAT data gives consistent results (βHE = 1.20-0.23 +0.21), 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.en_ZA
dc.description.librarianEM2018en_ZA
dc.identifier.citationAbdalla, H. et al. 2017. Characterizing the gamma-ray long-term variability of PKS2155 304 with HESS and Fermi-LAT. ASTRONOMY & ASTROPHYSICS 598, Article number A39.en_ZA
dc.identifier.issn0004-6361 (Print)
dc.identifier.issn1432-0746 (Online)
dc.identifier.urihttps://hdl.handle.net/10539/23786
dc.journal.titleASTRONOMY & ASTROPHYSICSen_ZA
dc.journal.volume598en_ZA
dc.language.isoenen_ZA
dc.publisherEDP Sciencesen_ZA
dc.rights© ESO, 2017en_ZA
dc.subjectGalaxies: activeen_ZA
dc.subjectBL Lacertae objects: individual: PKS 2155-304en_ZA
dc.subjectGalaxies: jetsen_ZA
dc.subjectGalaxies: nucleien_ZA
dc.subjectGamma rays: galaxiesen_ZA
dc.subjectRadiation mechanisms: non-thermalen_ZA
dc.subjectFighter aircraften_ZA
dc.subjectGalaxiesen_ZA
dc.subjectPower spectral densityen_ZA
dc.subjectRelativityen_ZA
dc.subjectSpectral densityen_ZA
dc.subjectBl lacertae objects: individual: pks 2155-304en_ZA
dc.titleCharacterizing the gamma-ray long-term variability of PKS2155 304 with HESS and Fermi-LATen_ZA
dc.typeArticleen_ZA
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