Evidence for VHE Gamma-ray Emission from the Distant BL Lac PG 1553+113
F. Aharonian
,
A.G. Akhperjanian
,
A.R. Bazer-Bachi
,
M. Beilicke
,
Wystan Benbow
,
David Berge
,
K. Bernlohr
,
C. Boisson
,
O. Bolz
,
V. Borrel
,
I. Braun
,
F. Breitling
,
A.M. Brown
,
R. Buhler
,
S. Carrigan
,
P.M. Chadwick
,
L.-M. Chounet
(1)
,
R. Cornils
,
L. Costamante
,
B. Degrange
(1)
,
H.J. Dickinson
,
A. Djannati-Ataï
(2)
,
L.O'C. Drury
,
G. Dubus
(1)
,
K. Egberts
,
D. Emmanoulopoulos
,
P. Espigat
(2)
,
F. Feinstein
(3)
,
G. Fontaine
(1)
,
S. Funk
,
Y. Gallant
(3)
,
B. Giebels
(1)
,
J.F. Glicenstein
,
P. Goret
,
C. Hadjichristidis
,
D. Hauser
,
M. Hauser
,
G. Heinzelmann
,
G. Henri
,
G. Hermann
,
J.A. Hinton
,
W. Hofmann
,
M. Holleran
,
Dieter Horns
,
A. Jacholkowska
(3)
,
O.C. de Jager
,
B. Khelifi
(1)
,
S. Klages
,
Nu. Komin
,
A. Konopelko
,
I.J. Latham
,
R. Le Gallou
,
A. Lemiere
(2)
,
M. Lemoine-Goumard
(1)
,
T. Lohse
,
J.M. Martin
,
O. Martineau-Huynh
(4)
,
A. Marcowith
,
C. Masterson
,
T.J.L. Mccomb
,
M. de Naurois
(4)
,
D. Nedbal
,
S.J. Nolan
,
A. Noutsos
,
K.J. Orford
,
J.L. Osborne
,
M. Ouchrif
(4)
,
M. Panter
,
G. Pelletier
,
S. Pita
(2)
,
G. Puhlhofer
,
M. Punch
(2)
,
B.C. Raubenheimer
,
M. Raue
,
S.M. Rayner
,
A. Reimer
,
O. Reimer
,
J. Ripken
,
L. Rob
,
L. Rolland
(4)
,
G. Rowell
,
V. Sahakian
,
L. Sauge
,
S. Schlenker
,
R. Schlickeiser
,
C. Schuster
,
U. Schwanke
,
M. Siewert
,
H. Sol
,
D. Spangler
,
R. Steenkamp
,
C. Stegmann
,
G. Superina
,
J.-P. Tavernet
(4)
,
R. Terrier
(2)
,
C.G. Theoret
(2)
,
M. Tluczykont
(1)
,
C. van Eldik
,
G. Vasileiadis
(3)
,
C. Venter
,
P. Vincent
(4)
,
H.J. Volk
,
S.J. Wagner
,
M. Ward
F. Aharonian
- Function : Author
- PersonId : 755280
- ORCID : 0000-0003-1157-3915
A.G. Akhperjanian
- Function : Author
A.R. Bazer-Bachi
- Function : Author
M. Beilicke
- Function : Author
Wystan Benbow
- Function : Author
David Berge
- Function : Author
K. Bernlohr
- Function : Author
C. Boisson
- Function : Author
- PersonId : 755462
- ORCID : 0000-0001-5893-1797
O. Bolz
- Function : Author
V. Borrel
- Function : Author
I. Braun
- Function : Author
F. Breitling
- Function : Author
A.M. Brown
- Function : Author
R. Buhler
- Function : Author
S. Carrigan
- Function : Author
P.M. Chadwick
- Function : Author
R. Cornils
- Function : Author
L. Costamante
- Function : Author
H.J. Dickinson
- Function : Author
L.O'C. Drury
- Function : Author
G. Dubus
- Function : Author
- PersonId : 746648
- IdHAL : guillaume-dubus
- ORCID : 0000-0002-5130-2514
- IdRef : 164946438
K. Egberts
- Function : Author
D. Emmanoulopoulos
- Function : Author
S. Funk
- Function : Author
J.F. Glicenstein
- Function : Author
P. Goret
- Function : Author
C. Hadjichristidis
- Function : Author
D. Hauser
- Function : Author
M. Hauser
- Function : Author
G. Heinzelmann
- Function : Author
G. Henri
- Function : Author
G. Hermann
- Function : Author
J.A. Hinton
- Function : Author
W. Hofmann
- Function : Author
M. Holleran
- Function : Author
Dieter Horns
- Function : Author
O.C. de Jager
- Function : Author
B. Khelifi
- Function : Author
- PersonId : 1145299
- IdHAL : bruno-khelifi
S. Klages
- Function : Author
Nu. Komin
- Function : Author
- PersonId : 755464
- ORCID : 0000-0003-3280-0582
A. Konopelko
- Function : Author
I.J. Latham
- Function : Author
R. Le Gallou
- Function : Author
M. Lemoine-Goumard
- Function : Author
- PersonId : 1416454
- IdHAL : marianne-lemoine-goumard
- IdRef : 111693608
T. Lohse
- Function : Author
- PersonId : 755171
- ORCID : 0000-0002-9751-7633
J.M. Martin
- Function : Author
A. Marcowith
- Function : Author
- PersonId : 174341
- IdHAL : alexandre-marcowith
- ORCID : 0000-0002-3971-0910
- IdRef : 114473609
C. Masterson
- Function : Author
T.J.L. Mccomb
- Function : Author
M. de Naurois
- Function : Author
- PersonId : 755312
- IdHAL : mathieu-de-naurois
- ORCID : 0000-0002-7245-201X
D. Nedbal
- Function : Author
S.J. Nolan
- Function : Author
A. Noutsos
- Function : Author
K.J. Orford
- Function : Author
J.L. Osborne
- Function : Author
M. Panter
- Function : Author
G. Pelletier
- Function : Author
G. Puhlhofer
- Function : Author
M. Punch
- Function : Author
- PersonId : 742769
- IdHAL : michael-punch
- ORCID : 0000-0002-4710-2165
- IdRef : 15174677X
B.C. Raubenheimer
- Function : Author
M. Raue
- Function : Author
S.M. Rayner
- Function : Author
A. Reimer
- Function : Author
- PersonId : 755465
- ORCID : 0000-0001-8604-7077
O. Reimer
- Function : Author
J. Ripken
- Function : Author
L. Rob
- Function : Author
L. Rolland
- Function : Author
- PersonId : 4321
- IdHAL : loic-rolland
- ORCID : 0000-0003-0589-9687
- IdRef : 090243080
G. Rowell
- Function : Author
- PersonId : 755359
- ORCID : 0000-0002-9516-1581
V. Sahakian
- Function : Author
L. Sauge
- Function : Author
S. Schlenker
- Function : Author
R. Schlickeiser
- Function : Author
C. Schuster
- Function : Author
U. Schwanke
- Function : Author
- PersonId : 755454
- ORCID : 0000-0002-1229-278X
M. Siewert
- Function : Author
H. Sol
- Function : Author
D. Spangler
- Function : Author
R. Steenkamp
- Function : Author
C. Stegmann
- Function : Author
G. Superina
- Function : Author
C. van Eldik
- Function : Author
- PersonId : 756115
- ORCID : 0000-0001-9669-645X
C. Venter
- Function : Author
- PersonId : 755527
- ORCID : 0000-0002-2666-4812
H.J. Volk
- Function : Author
S.J. Wagner
- Function : Author
M. Ward
- Function : Author
Abstract
The high-frequency peaked BL Lac PG 1553+113 was observed in 2005 with the H.E.S.S. stereoscopic array of imaging atmospheric-Cherenkov telescopes in Namibia. Using the H.E.S.S. standard analysis, an excess was measured at the 4.0 sigma level in these observations (7.6 hours live time). Three alternative, lower-threshold analyses yield >5 sigma excesses. The observed integral flux above 200 GeV is (4.8 +/- 1.3_{stat} +/- 1.0_{syst}) x10^{-12} cm^{-2} s^{-1}, and shows no evidence for variability. The measured energy spectrum is characterized by a very soft power law (photon index of Gamma=4.0 +/- 0.6). Although the redshift of PG 1553+113 is unknown, there are strong indications that it is greater than z=0.25 and possibly larger than z=0.78. The observed spectrum is interpreted in the context of VHE gamma-ray absorption by the Extragalactic Background Light, and is used to place an upper limit on the redshift of z<0.74.