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Deep broadband observations of the distant gamma-ray blazar PKS 1424+240
Authors
M Ackermann
M Ajello
+98 more
A Albert
S Archambault
T Aune
L Baldini
D Bastieri
B Behera
M Beilicke
R Bellazzini
W Benbow
K Berger
R Bird
E Bissaldi
J Biteau
J Bregeon
R Buehler
V Bugaev
S Buson
K Byrum
GA Caliandro
RA Cameron
PA Caraveo
JV Cardenzana
E Cavazzuti
M Cerruti
E Charles
X Chen
J Chiang
S Ciprini
L Ciupik
R Claus
MP Connolly
W Cui
S Cutini
F D'Ammando
A De Angelis
AOF De Bhróithe
J Dumm
M Errando
A Falcone
S Federici
Q Feng
JP Finley
H Fleischhack
L Fortson
A Furniss
N Galante
GH Gillanders
S Griffin
ST Griffiths
J Grube
G Gyuk
D Hanna
J Holder
G Hughes
TB Humensky
CA Johnson
P Kaaret
M Kertzman
Y Khassen
D Kieda
H Krawczynski
F Krennrich
S Kumar
MJ Lang
AS Madhavan
G Maier
A McCann
K Meagher
P Moriarty
R Mukherjee
D Nieto
RA Ong
AN Otte
N Park
M Pohl
A Popkow
H Prokoph
J Quinn
K Ragan
J Rajotte
LC Reyes
PT Reynolds
GT Richards
E Roache
GH Sembroski
K Shahinyan
D Staszak
I Telezhinsky
JV Tucci
J Tyler
A Varlotta
VV Vassiliev
S Vincent
SP Wakely
A Weinstein
R Welsing
A Wilhelm
DA Williams
Publication date
10 April 2014
Publisher
eScholarship, University of California
Abstract
We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z ≥ 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 ± 0.3) × 10 photons m s above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02 ± 0.08) × 10 photons m s above 120 GeV. The measured differential very high energy (VHE; E ≥ 100 GeV) spectral indices are Γ = 3.8 ± 0.3, 4.3 ± 0.6 and 4.5 ± 0.2 in 2009, 2011, and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than τ = 2, where it is postulated that any variability would be small and occur on timescales longer than a year if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics. © 2014. The American Astronomical Society. All rights reserved.. -7 -2 -1 -7 -2 -
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