VHE gamma-ray emission of PKS 2155-304: spectral and temporal variability
A. Abramowski
,
Fabio Acero
(1)
,
F. Aharonian
,
A. G. Akhperjanian
,
G. Anton
,
U. Barres de Almeida
,
A. R. Bazer-Bachi
(2)
,
Y. Becherini
(3)
,
B. Behera
,
W. Benbow
,
K. Bernlohr
,
A. Bochow
,
C. Boisson
(4)
,
J. Bolmont
(5)
,
V. Borrel
(2)
,
J. Brucker
,
F. Brun
(5)
,
P. Brun
(6)
,
R. Buhler
,
T. Bulik
,
I. Busching
,
T. Boutelier
(7)
,
P. M. Chadwick
,
A. Charbonnier
(5)
,
R. C. G. Chaves
,
A. Cheesebrough
,
J. Conrad
,
L. -M. Chounet
(8)
,
A. C. Clapson
,
G. Coignet
(9)
,
L. Costamante
,
M. Dalton
,
M. K. Daniel
,
I. D. Davids
,
B. Degrange
(8)
,
C. Deil
,
H. J. Dickinson
,
A. Djannati-Ataï
(10)
,
W. Domainko
,
L. O'C. Drury
,
F. Dubois
(9)
,
G. Dubus
(7)
,
J. Dyks
,
M. Dyrda
,
K. Egberts
,
P. Eger
,
P. Espigat
(3)
,
L. Fallon
,
C. Farnier
(1)
,
S. Fegan
(8)
,
F. Feinstein
(1)
,
M. V. Fernandes
,
A. Fiasson
(9)
,
A. Foerster
,
G. Fontaine
(8)
,
M. Fussling
,
S. Gabici
,
Y. A. Gallant
(1)
,
L. Gerard
(3)
,
D. Gerbig
,
B. Giebels
(8)
,
J. F. Glicenstein
(6)
,
B. Glueck
,
P. Goret
(6)
,
D. Goering
,
D. Hampf
,
M. Hauser
,
S. Heinz
,
G. Heinzelmann
,
G. Henri
(7)
,
G. Hermann
,
J. A. Hinton
,
A. Hoffmann
,
W. Hofmann
,
P. Hofverberg
,
M. Holleran
,
S. Hoppe
,
D. Horns
,
A. Jacholkowska
(5)
,
O. C. de Jager
,
C. Jahn
,
I. Jung
,
K. Katarzynski
,
U. Katz
,
S. Kaufmann
,
M. Kerschhaggl
,
D. Khangulyan
,
B. Khelifi
(8)
,
D. Keogh
,
D. Klochkov
,
W. Kluzniak
,
T. Kneiske
,
Nu. Komin
(6)
,
K. Kosack
(6)
,
R. Kossakowski
(9)
,
G. Lamanna
(9)
,
J. -P. Lenain
(4)
,
T. Lohse
,
C. -C. Lu
,
V. Marandon
(3)
,
A. Marcowith
(1)
,
Julien Masbou
(9)
,
D. Maurin
(5)
,
T. J. L. Mccomb
,
M. C. Medina
(4)
,
J. Mehault
(1)
,
R. Moderski
,
Emmanuel Moulin
(6)
,
M. Naumann-Godo
(8)
,
M. de Naurois
(5)
,
D. Nedbal
,
D. Nekrassov
,
N. Nguyen
,
B. Nicholas
,
J. Niemiec
,
S. J. Nolan
,
S. Ohm
,
J-F. Olive
(2)
,
E. de Ona Wilhelmi
,
B. Opitz
,
K. J. Orford
,
M. Ostrowski
,
M. Panter
,
M. Paz Arribas
,
G. Pedaletti
,
G. Pelletier
(7)
,
P. -O. Petrucci
(7)
,
S. Pita
(3)
,
G. Puehlhofer
,
M. Punch
(3)
,
A. Quirrenbach
,
B. C. Raubenheimer
,
M. Raue
,
S. M. Rayner
,
O. Reimer
,
M. Renaud
(3)
,
R. de Los Reyes
,
F. Rieger
,
J. Ripken
,
L. Rob
,
S. Rosier-Lees
(9)
,
G. Rowell
,
B. Rudak
,
C. B. Rulten
,
J. Ruppel
,
F. Ryde
,
V. Sahakian
,
A. Santangelo
,
R. Schlickeiser
,
F. M. Schoeck
,
A. Schoenwald
,
U. Schwanke
,
S. Schwarzburg
,
S. Schwemmer
,
A. Shalchi
,
I. Sushch
,
M. Sikora
,
J. L. Skilton
,
H. Sol
(4)
,
L. Stawarz
,
R. Steenkamp
,
C. Stegmann
,
F. Stinzing
,
G. Superina
(8)
,
A. Szostek
(7)
,
P. H. Tam
,
J. -P. Tavernet
(5)
,
R. Terrier
(3)
,
O. Tibolla
,
M. Tluczykont
,
K. Valerius
,
C. van Eldik
,
G. Vasileiadis
(1)
,
C. Venter
,
L. Venter
(4)
,
J. P. Vialle
(9)
,
A. Viana
,
P. Vincent
(5)
,
M. Vivier
(6)
,
H. J. Voelk
,
F. Volpe
(8)
,
S. Vorobiov
(1)
,
S. J. Wagner
,
M. Ward
,
A. A. Zdziarski
,
A. Zech
(4)
,
H. -S. Zechlin
1
LPTA -
Laboratoire de Physique Théorique et Astroparticules
2 CESR - Centre d'étude spatiale des rayonnements
3 APC (UMR_7164) - AstroParticule et Cosmologie
4 LUTH (UMR_8102) - Laboratoire Univers et Théories
5 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
6 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
7 LAOG - Laboratoire d'Astrophysique de Grenoble
8 LLR - Laboratoire Leprince-Ringuet
9 LAPP - Laboratoire d'Annecy de Physique des Particules
10 APC - AHE - APC - Astrophysique des Hautes Energies
2 CESR - Centre d'étude spatiale des rayonnements
3 APC (UMR_7164) - AstroParticule et Cosmologie
4 LUTH (UMR_8102) - Laboratoire Univers et Théories
5 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
6 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
7 LAOG - Laboratoire d'Astrophysique de Grenoble
8 LLR - Laboratoire Leprince-Ringuet
9 LAPP - Laboratoire d'Annecy de Physique des Particules
10 APC - AHE - APC - Astrophysique des Hautes Energies
A. Abramowski
- Function : Author
Fabio Acero
- Function : Author
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F. Aharonian
- Function : Author
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A. G. Akhperjanian
- Function : Author
G. Anton
- Function : Author
U. Barres de Almeida
- Function : Author
B. Behera
- Function : Author
W. Benbow
- Function : Author
K. Bernlohr
- Function : Author
A. Bochow
- Function : Author
C. Boisson
- Function : Author
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J. Brucker
- Function : Author
F. Brun
- Function : Author
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P. Brun
- Function : Author
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R. Buhler
- Function : Author
T. Bulik
- Function : Author
I. Busching
- Function : Author
P. M. Chadwick
- Function : Author
R. C. G. Chaves
- Function : Author
A. Cheesebrough
- Function : Author
J. Conrad
- Function : Author
A. C. Clapson
- Function : Author
L. Costamante
- Function : Author
M. Dalton
- Function : Author
M. K. Daniel
- Function : Author
I. D. Davids
- Function : Author
C. Deil
- Function : Author
H. J. Dickinson
- Function : Author
W. Domainko
- Function : Author
L. O'C. Drury
- Function : Author
G. Dubus
- Function : Author
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J. Dyks
- Function : Author
M. Dyrda
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K. Egberts
- Function : Author
P. Eger
- Function : Author
L. Fallon
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S. Fegan
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M. V. Fernandes
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A. Foerster
- Function : Author
M. Fussling
- Function : Author
S. Gabici
- Function : Author
D. Gerbig
- Function : Author
B. Glueck
- Function : Author
D. Goering
- Function : Author
D. Hampf
- Function : Author
M. Hauser
- Function : Author
S. Heinz
- Function : Author
G. Heinzelmann
- Function : Author
G. Hermann
- Function : Author
J. A. Hinton
- Function : Author
A. Hoffmann
- Function : Author
W. Hofmann
- Function : Author
P. Hofverberg
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M. Holleran
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S. Hoppe
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D. Horns
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O. C. de Jager
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C. Jahn
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I. Jung
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K. Katarzynski
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U. Katz
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S. Kaufmann
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M. Kerschhaggl
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D. Keogh
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D. Klochkov
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K. Kosack
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J. -P. Lenain
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T. Lohse
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C. -C. Lu
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V. Marandon
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A. Marcowith
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Julien Masbou
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D. Maurin
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T. J. L. Mccomb
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R. Moderski
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M. de Naurois
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D. Nedbal
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E. de Ona Wilhelmi
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C. B. Rulten
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S. Schwarzburg
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S. Schwemmer
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A. Shalchi
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M. Sikora
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J. L. Skilton
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L. Stawarz
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R. Steenkamp
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C. Stegmann
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F. Stinzing
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P. H. Tam
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O. Tibolla
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A. Viana
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H. J. Voelk
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H. -S. Zechlin
- Function : Author
Abstract
Observations of very high energy gamma-rays from blazars provide information about acceleration mechanisms occurring in their innermost regions. Studies of variability in these objects allow a better understanding of the mechanisms at play. To investigate the spectral and temporal variability of VHE (>100 GeV) gamma-rays of the well-known high-frequency-peaked BL Lac object PKS 2155-304 with the H.E.S.S. imaging atmospheric Cherenkov telescopes over a wide range of flux states. Data collected from 2005 to 2007 are analyzed. Spectra are derived on time scales ranging from 3 years to 4 minutes. Light curve variability is studied through doubling timescales and structure functions, and is compared with red noise process simulations. The source is found to be in a low state from 2005 to 2007, except for a set of exceptional flares which occurred in July 2006. The quiescent state of the source is characterized by an associated mean flux level of 4.32 +/-0.09 x 10^-11 cm^-2 s^-1 above 200 GeV, or approximately 15% of the Crab Nebula, and a power law photon index of 3.53 +/-0.06. 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 behaviour at low and high fluxes,which is a new phenomenon in VHE gamma-ray emitting blazars. The variability amplitude characterized by the fractional r.m.s. is strongly energy-dependent and is proportional to E^(0.19 +/- 0.01). The light curve r.m.s. correlates with the flux. This is the signature of a multiplicative process which can be accounted for as a red noise with a Fourier index of ~2. This unique data set shows evidence for a low level gamma-ray emission state from PKS 2155-304, which possibly has a different origin than the outbursts. The discovery of the light curve lognormal behaviour might be an indicator ..