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H.E.S.S. observations of PKS 2155-304

Aharonian, F.; Akhperjanian, A.G.; Aye, K.-M.; Bazer-Bachi, A.R.; Beilicke, M.; Benbow, W.; Berge, D.; Berghaus, P.; Bernlöhr, K.; Bolz, O.; Boisson, C.; Borgmeier, C.; Breitling, F.; Brown, A.M.; Bussons Gordo, J.; Chadwick, P.M.; Chitnis, V.R.; Chounet, L.-M.; Cornils, R.; Costamante, L.; Degrange, B.; Djannati-Ataï, A.; Drury, L. O'C.; Ergin, T.; Espigat, P.; Feinstein, F.; Fleury, P.; Fontaine, G.; Funk, S.; Gallant, Y.A.; Giebels, B.; Gillessen, S.; Goret, P.; Guy, J.; Hadjichristidis, C.; Hauser, M.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J.A.; Hofmann, W.; Holleran, M.; Horns, D.; de Jager, O.C.; Jung, I.; Khélifi, B.; Komin, N.; Konopelko, A.; Latham, I.J.; Le Gallou, R.; Lemoine, M.; Lemière, A.; Leroy, N.; Lohse, T.; Marcowith, A.; Masterson, C.; McComb, T.J.L.; de Naurois, M.; Nolan, S.J.; Noutsos, A.; Orford, K.J.; Osborne, J.L.; Ouchrif, M.; Panter, M.; Pelletier, G.; Pita, S.; Pohl, M.; Pühlhofer, G.; Punch, M.; Raubenheimer, B.C.; Raue, M.; Raux, J.; Rayner, S....

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Authors

F. Aharonian

A.G. Akhperjanian

K.-M. Aye

A.R. Bazer-Bachi

M. Beilicke

W. Benbow

D. Berge

P. Berghaus

K. Bernlöhr

O. Bolz

C. Boisson

C. Borgmeier

F. Breitling

A.M. Brown

J. Bussons Gordo

V.R. Chitnis

L.-M. Chounet

R. Cornils

L. Costamante

B. Degrange

A. Djannati-Ataï

L. O'C. Drury

T. Ergin

P. Espigat

F. Feinstein

P. Fleury

G. Fontaine

S. Funk

Y.A. Gallant

B. Giebels

S. Gillessen

P. Goret

J. Guy

C. Hadjichristidis

M. Hauser

G. Heinzelmann

G. Henri

G. Hermann

J.A. Hinton

W. Hofmann

M. Holleran

D. Horns

O.C. de Jager

I. Jung

B. Khélifi

N. Komin

A. Konopelko

I.J. Latham

R. Le Gallou

M. Lemoine

A. Lemière

N. Leroy

T. Lohse

A. Marcowith

C. Masterson

T.J.L. McComb

M. de Naurois

A. Noutsos

K.J. Orford

M. Ouchrif

M. Panter

G. Pelletier

S. Pita

M. Pohl

G. Pühlhofer

M. Punch

B.C. Raubenheimer

M. Raue

J. Raux

S.M. Rayner

I. Redondo

A. Reimer

O. Reimer

J. Ripken

M. Rivoal

L. Rob

L. Rolland

G. Rowell

V. Sahakian

L. Saugé

S. Schlenker

R. Schlickeiser

C. Schuster

U. Schwanke

M. Siewert

H. Sol

R. Steenkamp

C. Stegmann

J.-P. Tavernet

C.G. Théoret

M. Tluczykont

D.J. van der Walt

G. Vasileiadis

P. Vincent

B. Visser

H.J. Völk

S.J. Wagner



Abstract

The high-frequency peaked BL Lac PKS 2155-304 at redshift z=0.117 has been detected with high significance (~45sigma) at energies greater than 160 GeV, using the H.E.S.S. stereoscopic array of imaging air-Cherenkov telescopes in Namibia. A strong signal is found in each of the data sets corresponding to the dark periods of July and October, 2002, and June-September, 2003. The observed flux of VHE gamma rays shows variability on time scales of months, days, and hours. The monthly-averaged integral flux above 300 GeV varies between 10% and 60% of the flux observed from the Crab Nebula. Energy spectra are measured for these individual periods of data taking and are characterized by a steep power law with a time-averaged photon index of Gamma=3.32±0.06. An improved chi2 per degree of freedom is found when either a power law with an exponential cutoff energy or a broken power law are fit to the time-averaged energy spectrum. However, the significance of the improvement is marginal (~2sigma). The suggested presence of features in the energy spectrum may be intrinsic to the emission from the blazar, or an indication of absorption of TeV gamma rays by the extragalactic infrared background light

Citation

Aharonian, F., Akhperjanian, A., Aye, K., Bazer-Bachi, A., Beilicke, M., Benbow, W., …Wagner, S. (2005). H.E.S.S. observations of PKS 2155-304. Astronomy & Astrophysics, 430(3), 865-875. https://doi.org/10.1051/0004-6361%3A20041853

Journal Article Type Article
Publication Date Feb 1, 2005
Deposit Date May 29, 2008
Publicly Available Date May 29, 2008
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 430
Issue 3
Pages 865-875
DOI https://doi.org/10.1051/0004-6361%3A20041853
Keywords Active galaxies, BL Lacertae objects, Gamma rays.

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Copyright Statement
Reproduced with permission from Astronomy & Astrophysics, © ESO





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