36823
2011
2011
eng
10
2
733
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Gamma-ray observations of the Be/Pulsar binary 1A 0535+262 during a Giant X-Ray outburst
Giant X-ray outbursts, with luminosities of about 10(37) erg s(-1), are observed roughly every five years from the nearby Be/pulsar binary 1A 0535+262. In this article, we present observations of the source with VERITAS at very high energies (VHEs; E > 100 GeV) triggered by the X-ray outburst in 2009 December. The observations started shortly after the onset of the outburst and provided comprehensive coverage of the episode, as well as the 111 day binary orbit. No VHE emission is evident at any time. We also examined data from the contemporaneous observations of 1A 0535+262 with the Fermi/Large Area Telescope at high-energy photons (E > 0.1 GeV) and failed to detect the source at GeV energies. The X-ray continua measured with the Swift/X-Ray Telescope and the RXTE/PCA can be well described by the combination of blackbody and Comptonized emission from thermal electrons. Therefore, the gamma-ray and X-ray observations suggest the absence of a significant population of non-thermal particles in the system. This distinguishes 1A 0535+262 from those Be X-ray binaries (such as PSR B1259-63 and LS I +61 degrees 303) that have been detected at GeV-TeV energies. We discuss the implications of the results on theoretical models.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/733/2/96
0004-637X
wos:2011-2013
96
WOS:000290676100023
Cui, W (reprint author), Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA., avarlott@purdue.edu; cui@purdue.edu; gernot.maier@desy.de; avarlott@purdue.edu
US Department of Energy; US National Science Foundation; Smithsonian
Institution; NSERC in Canada; Science Foundation Ireland; STFC in the
UK; Helmholtz Association; NASA; Purdue University
V. A. Acciari
E. Aliu
M. Araya
T. Arlen
T. Aune
M. Beilicke
W. Benbow
S. M. Bradbury
J. H. Buckley
V. Bugaev
K. Byrum
A. Cannon
A. Cesarini
L. Ciupik
E. Collins-Hughes
W. Cui
R. Dickherber
C. Duke
A. Falcone
J. P. Finley
L. Fortson
A. Furniss
N. Galante
D. Gall
S. Godambe
S. Griffin
R. Guenette
G. Gyuk
D. Hanna
J. Holder
G. Hughes
C. M. Hui
T. B. Humensky
A. Imran
P. Kaaret
M. Kertzman
H. Krawczynski
F. Krennrich
A. S. Madhavan
G. Maier
P. Majumdar
S. McArthur
P. Moriarty
R. A. Ong
A. N. Otte
D. Pandel
N. Park
J. S. Perkins
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
H. J. Rose
D. B. Saxon
G. H. Sembroski
G. D. Sentuerk
A. W. Smith
G. Tesic
M. Theiling
S. Thibadeau
A. Varlotta
S. Vincent
M. Vivier
S. P. Wakely
J. E. Ward
T. C. Weekes
A. Weinstein
T. Weisgarber
S. Weng
D. A. Williams
M. Wood
B. Zitzer
eng
uncontrolled
acceleration of particles
eng
uncontrolled
binaries: general
eng
uncontrolled
gamma rays: general
eng
uncontrolled
stars: individual (1A 0535+262)
Institut für Physik und Astronomie
Referiert
37935
2014
2014
eng
8
1
785
article
IOP Publ. Ltd.
Bristol
VERITAS Collaboration, Fermi LAT Collaboration
1
--
--
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Deep broadband observations of the distant gamma-ray blazar PKS 1424+240
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) x 10(-7) photons m(-2) s(-1) above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02 +/- 0.08) x 10-7 photons m(-2) s(-1) above 120 GeV. The measured differential very high energy (VHE; E >= 100 GeV) spectral indices are Gamma = 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 tau = 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.
The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
10.1088/2041-8205/785/1/L16
2041-8205
2041-8213
wos:2014
L16
WOS:000334345000016
Archambault, S (reprint author), McGill Univ, Dept Phys, 3600 Univ St, Montreal, PQ H3A 2T8, Canada., amy.furniss@gmail.com
U.S. Department of Energy Office of Science; U.S. National Science
Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation
Ireland [SFI 10/RFP/AST2748]; STFC in the UK; NASA through the Space
Telescope Science Institute [HST-GO-12863]; NASA [NAS 5-26555]; INAF in
Italy; CNES in France
S. Archambault
T. Aune
B. Behera
M. Beilicke
W. Benbow
K. Berger
R. Bird
Jonathan Biteau
V. Bugaev
K. Byrum
J. V. Cardenzana
M. Cerruti
Xuhui Chen
L. Ciupik
M. P. Connolly
Wei Cui
J. Dumm
M. Errando
A. Falcone
Simone Federici
Q. Feng
J. P. Finley
H. Fleischhack
L. Fortson
A. Furniss
N. Galante
G. H. Gillanders
S. Griffin
S. T. Griffiths
J. Grube
G. Gyuk
D. Hanna
J. Holder
G. Hughes
T. B. Humensky
C. A. Johnson
P. Kaaret
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
S. Kumar
M. J. Lang
A. S. Madhavan
G. Maier
A. McCann
K. Meagher
P. Moriarty
R. Mukherjee
Daniel Nieto
R. A. Ong
A. N. Otte
N. Park
Martin Pohl
A. Popkow
H. Prokoph
J. Quinn
K. Ragan
J. Rajotte
L. C. Reyes
P. T. Reynolds
G. T. Richards
E. Roache
G. H. Sembroski
K. Shahinyan
D. Staszak
Igor O. Telezhinsky
J. V. Tucci
J. Tyler
A. Varlotta
V. V. Vassiliev
S. Vincent
S. P. Wakely
A. Weinstein
R. Welsing
Alina Wilhelm
D. A. Williams
Margit Ackermann
M. Ajello
A. Albert
L. Baldini
D. Bastieri
R. Bellazzini
E. Bissaldi
Johan Bregeon
R. Buehler
S. Buson
G. A. Caliandro
R. A. Cameron
P. A. Caraveo
E. Cavazzuti
E. Charles
J. Chiang
S. Ciprini
R. Claus
S. Cutini
A. de Angelis
F. de Palma
C. D. Dermer
S. W. Digel
L. Di Venere
P. S. Drell
C. Favuzzi
A. Franckowiak
P. Fusco
F. Gargano
D. Gasparrini
N. Giglietto
F. Giordano
M. Giroletti
I. A. Grenier
S. Guiriec
T. Jogler
M. Kuss
S. Larsson
L. Latronico
F. Longo
F. Loparco
P. Lubrano
G. M. Madejski
M. Mayer
Mario Nicola Mazziotta
P. F. Michelson
T. Mizuno
M. E. Monzani
Aldo Morselli
S. Murgia
E. Nuss
T. Ohsugi
J. F. Ormes
D. Paneque
J. S. Perkins
F. Piron
G. Pivato
S. Raino
M. Razzano
A. Reimer
Olaf Reimer
S. Ritz
M. Schaal
C. Sgro
E. J. Siskind
P. Spinelli
H. Takahashi
L. Tibaldo
M. Tinivella
E. Troja
G. Vianello
M. Werner
M. Wood
eng
uncontrolled
BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
39244
2015
2015
eng
9
1
799
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Veritas observations of the BL LAC OBJECT PG 1553+113
We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560 GeV, is well described by a power law with a spectral index of 4.33 +/- 0.09. The time-averaged integral flux above 200 GeV measured for this period was (1.69 +/- 0.06) x 10(-11) photons cm(-2) s(-1), corresponding to 6.9% of the Crab Nebula flux. We also present the combined gamma-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100 MeV to 560 GeV. The data are well fit by a power law with an exponential cutoff at 101.9 +/- 3.2 GeV. The origin of the cutoff could be intrinsic to PG 1553+113 or be due to the gamma-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of z > 0.395 based on optical/UV observations of PG 1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of z <= 0.62. A strongly elevated mean flux of (2.50 +/- 0.14) x10(-11) photons cm(-2) s(-1) (10.3% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as (4.44 +/- 0.71) x10(-11) photons cm(-2) s(-1) (18.3% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a chi(2) probability for a steady flux of 0.03%.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/799/1/7
0004-637X
1538-4357
wos:2015
7
WOS:000348214500007
Aliu, E (reprint author), Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA.
U.S. Department of Energy Office of Science; U.S. National Science
Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation
Ireland [SFI 10/RFP/AST2748]; STFC in the U.K.
E. Aliu
A. Archer
T. Aune
Anna Barnacka
B. Behera
M. Beilicke
W. Benbow
K. Berger
R. Bird
J. H. Buckley
V. Bugaev
K. Byrum
J. V. Cardenzana
M. Cerruti
Xuhui Chen
L. Ciupik
M. P. Connolly
Wei Cui
H. J. Dickinson
J. Dumm
J. D. Eisch
M. Errando
A. Falcone
Simone Federici
Q. Feng
J. P. Finley
P. Fortin
L. Fortson
A. Furniss
N. Galante
G. H. Gillanders
S. Griffin
S. T. Griffiths
J. Grube
G. Gyuk
Nils Hakansson
D. Hanna
J. Holder
G. Hughes
T. B. Humensky
C. A. Johnson
P. Kaaret
P. Kar
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
S. Kumar
M. J. Lang
A. Madhavan
S. McArthur
A. McCann
K. Meagher
J. Millis
P. Moriarty
Daniel Nieto
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
Martin Pohl
A. Popkow
H. Prokoph
Elisa Pueschel
J. Quinn
K. Ragan
J. Rajotte
L. C. Reyes
P. T. Reynolds
G. T. Richards
E. Roache
G. H. Sembroski
K. Shahinyan
D. Staszak
Igor O. Telezhinsky
J. V. Tucci
J. Tyler
A. Varlotta
V. V. Vassiliev
S. P. Wakely
A. Weinstein
R. Welsing
Alina Wilhelm
D. A. Williams
B. Zitzer
eng
uncontrolled
BL Lacertae objects: general
Institut für Physik und Astronomie
Referiert
37769
2014
2014
eng
9
2
788
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Test of models of the cosmic infrared background with multiwavelength observations of the blazar 1ES 1218+30.4 IN 2009
We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and gamma-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, > 100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum-the first with simultaneous X-ray and VHE gamma-ray energy spectra-is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from the optical/infrared extragalactic background light (EBL) via gamma VHE +gamma EBL -> e(+) e(-)pair-creation processes. We model the data with a one-zone synchrotron self-Compton (SSC) emission model and with the extragalactic absorption predicted by several recent EBL models. We find that the observations are consistent with the SSC scenario and all the EBL models considered in this work. We discuss observational and theoretical avenues to improve on the EBL constraints.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/788/2/158
0004-637X
1538-4357
wos:2014
158
WOS:000337466200061
Archambault, S (reprint author), McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada.
U.S. Department of Energy Office of Science; U.S. National Science
Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation
Ireland [SFI 10/RFP/AST2748]; STFC in the U.K
S. Archambault
T. Arlen
T. Aune
M. Beilicke
W. Benbow
R. Bird
Markus Boettcher
A. Bouvier
J. H. Buckley
V. Bugaev
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
R. Dickherber
J. Dumm
M. Errando
A. Falcone
Simone Federici
Q. Feng
J. P. Finley
L. Fortson
A. Furniss
N. Galante
D. Gall
A. III. Garson
G. H. Gillanders
S. Griffin
J. Grube
C. Gusbar
G. Gyuk
D. Hanna
J. Holder
G. Hughes
P. Kaaret
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
A. Lamerato
M. J. Lang
K. Li
A. S. Madhavan
G. Maier
P. Majumdar
S. McArthur
A. McCann
J. Millis
P. Moriarty
R. Mukherjee
D. Nieto
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
Martin Pohl
A. Popkow
H. Prokoph
J. Quinn
K. Ragan
P. T. Reynolds
G. T. Richards
E. Roache
P. Roustazadeh
D. B. Saxon
G. H. Sembroski
G. D. Senturk
C. Skole
D. Staszak
Igor O. Telezhinsky
G. Tesic
M. Theiling
A. Varlotta
V. V. Vassiliev
S. Vincent
S. P. Wakely
A. Weinstein
R. Welsing
D. A. Williams
B. Zitzer
eng
uncontrolled
BL Lacertae objects: general
eng
uncontrolled
BL Lacertae objects: individual (1ES1218+30.4)
eng
uncontrolled
cosmic background radiation
eng
uncontrolled
diffuse radiation
eng
uncontrolled
galaxies: jets
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
35614
2012
2012
eng
14
2
757
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Constraints on cosmic rays, magnetic fields, and dark matter fromgamma-ray observations of the coma cluster of galaxies with veritas and fermi
Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) x 10(-8) photonsm(-2) s(-1) (VERITAS, >220 GeV) and similar to 2 x 10(-6) photonsm(-2) s(-1) (Fermi, 1-3GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be < 16% from VERITAS data and <1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of similar to(2-5.5) mu G, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark matter (DM) dominated, the VERITAS upper limits have been used to place constraints on the thermally averaged product of the total self-annihilation cross section and the relative velocity of the DM particles, <sigma nu >.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/757/2/123
0004-637X
wos:2011-2013
123
WOS:000309108500016
Arlen, T (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA., pohlmadq@gmail.com; christoph.pfrommer@h-its.org
U.S. Department of Energy Office of Science; U.S. National Science
Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation
Ireland [SFI 10/RFP/AST2748]; STFC in the U.K; National Aeronautics and
Space Administration; Department of Energy in the United States;
Commissariat a l'Energie Atomique; Centre National de la Recherche
Scientifique/Institut National de Physique Nucleaire et de Physique des
Particules in France; Agenzia Spaziale Italiana; Istituto Nazionale di
Fisica Nucleare in Italy; Ministry of Education, Culture, Sports,
Science and Technology (MEXT); High Energy Accelerator Research
Organization (KEK); Japan Aerospace Exploration Agency (JAXA) in Japan;
K. A. Wallenberg Foundation; Swedish Research Council; Swedish National
Space Board in Sweden; Istituto Nazionale di Astrofisica in Italy;
Centre National d'Etudes Spatiales in France; Klaus Tschira Foundation;
NSF [AST-0908480]
T. Arlen
T. Aune
M. Beilicke
W. Benbow
A. Bouvier
J. H. Buckley
V. Bugaev
K. Byrum
A. Cannon
A. Cesarini
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
R. Dickherber
J. Dumm
A. Falcone
S. Federici
Q. Feng
J. P. Finley
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
S. Godambe
S. Griffin
J. Grube
G. Gyuk
J. Holder
H. Huan
G. Hughes
T. B. Humensky
A. Imran
P. Kaaret
N. Karlsson
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
K. Lee
A. S. Madhavan
G. Maier
P. Majumdar
S. McArthur
A. McCann
P. Moriarty
R. Mukherjee
T. Nelson
A. O'Faolain de Bhroithe
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
J. Ruppel
D. B. Saxon
M. Schroedter
G. H. Sembroski
C. Skole
A. W. Smith
Igor O. Telezhinsky
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
A. Varlotta
M. Vivier
S. P. Wakely
J. E. Ward
A. Weinstein
R. Welsing
D. A. Williams
B. Zitzer
C. Pfrommer
A. Pinzke
eng
uncontrolled
cosmic rays
eng
uncontrolled
dark matter
eng
uncontrolled
galaxies: clusters: general
eng
uncontrolled
galaxies: clusters: individual (Coma (ACO 1656))
eng
uncontrolled
gamma rays: galaxies: clusters
eng
uncontrolled
magnetic fields
Institut für Physik und Astronomie
Referiert
35697
2012
2012
eng
7
2
755
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Multiwavelength observations of the AGN 1ES 0414+009 with veritas, FERMI-LAT, SWIFT-XRT, AND MDM
We present observations of the BL Lac object 1ES 0414+009 in the >200 GeV gamma-ray band by the VERITAS array of Cherenkov telescopes. 1ES 0414+009 was observed by VERITAS between 2008 January and 2011 February, resulting in 56.2 hr of good quality pointed observations. These observations resulted in a detection of 822 events from the source corresponding to a statistical significance of 6.4 standard deviations (6.4 sigma) above the background. The source flux, showing no evidence for variability, is measured as (5.2 +/- 1.1(stat) +/- 2.6(sys)) x 10(-12) photons cm(-2) s(-1) above 200 GeV, equivalent to approximately 2% of the Crab Nebula flux above this energy. The differential photon spectrum from 230 GeV to 850 GeV is well fit by a power law with a photon index of Gamma = 3.4 +/- 0.5(stat) +/- 0.3(sys) and a flux normalization of (1.6 +/- 0.3(stat) +/- 0.8(sys)) x 10(-11) photons cm(-2) s(-1) at 300 GeV. We also present multiwavelength results taken in the optical (MDM), x-ray (Swift-XRT), and GeV (Fermi-LAT) bands and use these results to construct a broadband spectral energy distribution (SED). Modeling of this SED indicates that homogenous one-zone leptonic scenarios are not adequate to describe emission from the system, with a lepto-hadronic model providing a better fit to the data.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/755/2/118
0004-637X
wos:2011-2013
118
WOS:000307791400035
Aliu, E (reprint author), Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA., aw.smith@utah.edu
U.S. Department of Energy Office of Science; U.S. National Science
Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation
Ireland [SFI 10/RFP/AST2748]; STFC in the U.K.
E. Aliu
S. Archambault
T. Arlen
T. Aune
M. Beilicke
W. Benbow
Markus Boettcher
A. Bouvier
V. Bugaev
A. Cannon
A. Cesarini
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
R. Dickherber
J. Dumm
M. Errando
A. Falcone
Stefania Federici
Q. Feng
J. P. Finley
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
S. Godambe
S. Griffin
J. Grube
G. Gyuk
D. Hanna
J. Holder
H. Huan
G. Hughes
C. M. Hui
A. Imran
O. Jameil
P. Kaaret
N. Karlsson
M. Kertzman
J. Kerr
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
M. J. Lang
K. Lee
A. S. Madhavan
P. Majumdar
S. McArthur
A. McCann
P. Moriarty
R. Mukherjee
T. Nelson
A. O'Faolain de Bhroithe
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
A. Pichel
Martin Pohl
J. Quinn
K. Ragan
P. T. Reynolds
E. Roache
J. Ruppel
D. B. Saxon
M. Schroedter
G. H. Sembroski
G. D. Sentuerk
A. W. Smith
D. Staszak
M. Stroh
Igor O. Telezhinsky
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
A. Varlotta
V. V. Vassiliev
M. Vivier
S. P. Wakely
J. E. Ward
A. Weinstein
R. Welsing
D. A. Williams
B. Zitzer
eng
uncontrolled
BL Lacertae objects: individual (1ES 0414+009, ERJ0416+011)
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
36123
2012
2012
eng
7
2
746
article
IOP Publ. Ltd.
Bristol
1
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Veritas observations of day-scale flaring of M 87 in 2010 April
VERITAS has been monitoring the very-high-energy (VHE; > 100 GeV) gamma-ray activity of the radio galaxy M87 since 2007. During 2008, flaring activity on a timescale of a few days was observed with a peak flux of (0.70 +/- 0.16) x 10(-11) cm(-2) s(-1) at energies above 350 GeV. In 2010 April, VERITAS detected a flare from M 87 with peak flux of (2.71 +/- 0.68) x 10(-11) cm(-2) s(-1) for E > 350 GeV. The source was observed for six consecutive nights during the flare, resulting in a total of 21 hr of good-quality data. The most rapid flux variation occurred on the trailing edge of the flare with an exponential flux decay time of 0.90(-0.15)(+0.22) days. The shortest detected exponential rise time is three times as long, at 2.87(+1.65)(-0.99) days. The quality of the data sample is such that spectral analysis can be performed for three periods: rising flux, peak flux, and falling flux. The spectra obtained are consistent with power-law forms. The spectral index at the peak of the flare is equal to 2.19 +/- 0.07. There is some indication that the spectrum is softer in the falling phase of the flare than the peak phase, with a confidence level corresponding to 3.6 standard deviations. We discuss the implications of these results for the acceleration and cooling rates of VHE electrons in M 87 and the constraints they provide on the physical size of the emitting region.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/746/2/141
0004-637X
wos:2011-2013
141
WOS:000300406300027
Aliu, E (reprint author), Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA., cmhui@physics.utah.edu
U.S. Department of Energy Office of Science; U.S. National Science
Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation
Ireland (SFI) [10/RFP/AST2748]; STFC in the UK
E. Aliu
T. Arlen
T. Aune
M. Beilicke
W. Benbow
A. Bouvier
S. M. Bradbury
J. H. Buckley
V. Bugaev
K. Byrum
A. Cannon
A. Cesarini
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
R. Dickherber
C. Duke
M. Errando
A. Falcone
J. P. Finley
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
S. Godambe
S. Griffin
J. Grube
R. Guenette
G. Gyuk
D. Hanna
J. Holder
H. Huan
G. Hughes
C. M. Hui
T. B. Humensky
A. Imran
P. Kaaret
N. Karlsson
M. Kertzman
D. Kieda
H. Krawczynski
F. Krennrich
M. J. Lang
S. LeBohec
A. S. Madhavan
G. Maier
P. Majumdar
S. McArthur
A. McCann
P. Moriarty
R. Mukherjee
P. D. Nunez
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
A. Pichel
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
H. J. Rose
J. Ruppel
D. B. Saxon
M. Schroedter
G. H. Sembroski
G. D. Sentuerk
C. Skole
D. Staszak
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
J. Tyler
A. Varlotta
V. V. Vassiliev
S. Vincent
M. Vivier
S. P. Wakely
J. E. Ward
T. C. Weekes
A. Weinstein
T. Weisgarber
D. A. Williams
B. Zitzer
eng
uncontrolled
galaxies: individual (M 87, VER J1230+123)
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
36045
2012
2012
eng
12
6
85
article
American Physical Society
College Park
1
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VERITAS deep observations of the dwarf spheroidal galaxy Segue 1
The VERITAS array of Cherenkov telescopes has carried out a deep observational program on the nearby dwarf spheroidal galaxy Segue 1. We report on the results of nearly 48 hours of good quality selected data, taken between January 2010 and May 2011. No significant gamma-ray emission is detected at the nominal position of Segue 1, and upper limits on the integrated flux are derived. According to recent studies, Segue 1 is the most dark matter-dominated dwarf spheroidal galaxy currently known. We derive stringent bounds on various annihilating and decaying dark matter particle models. The upper limits on the velocity-weighted annihilation cross-section are <sigma upsilon >(95%) (CL) less than or similar to 10(-23) cm(3) s(-1), improving our limits from previous observations of dwarf spheroidal galaxies by at least a factor of 2 for dark matter particle masses m(chi) greater than or similar to 300 GeV. The lower limits on the decay lifetime are at the level of tau(95%) (CL) greater than or similar to 10(24) s. Finally, we address the interpretation of the cosmic ray lepton anomalies measured by ATIC and PAMELA in terms of dark matter annihilation, and show that the VERITAS observations of Segue 1 disfavor such a scenario.
Physical review : D, Particles, fields, gravitation, and cosmology
10.1103/PhysRevD.85.062001
1550-7998
wos:2011-2013
062001
WOS:000301117000003
Vivier, M (reprint author), Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA., mvivier@bartol.udel.edu
US Department of Energy Office of Science; US National Science
Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation
Ireland [SFI 10/RFP/AST2748]; STFC in the United Kingdom
E. Aliu
S. Archambault
T. Arlen
T. Aune
M. Beilicke
W. Benbow
A. Bouvier
S. M. Bradbury
J. H. Buckley
V. Bugaev
K. Byrum
A. Cannon
A. Cesarini
J. L. Christiansen
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
G. Decerprit
R. Dickherber
J. Dumm
M. Errando
A. Falcone
Q. Feng
F. Ferrer
J. P. Finley
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
S. Godambe
S. Griffin
J. Grube
G. Gyuk
D. Hanna
J. Holder
H. Huan
G. Hughes
T. B. Humensky
P. Kaaret
N. Karlsson
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
K. Lee
A. S. Madhavan
G. Maier
P. Majumdar
S. McArthur
A. McCann
P. Moriarty
R. Mukherjee
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
H. J. Rose
J. Ruppel
D. B. Saxon
M. Schroedter
G. H. Sembroski
G. D. Sentuerk
C. Skole
A. W. Smith
D. Staszak
Igor O. Telezhinsky
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
A. Varlotta
V. V. Vassiliev
S. Vincent
M. Vivier
R. G. Wagner
S. P. Wakely
J. E. Ward
T. C. Weekes
A. Weinstein
T. Weisgarber
D. A. Williams
B. Zitzer
Institut für Physik und Astronomie
Referiert
36480
2011
2011
eng
7
2
742
article
IOP Publ. Ltd.
Bristol
VERITAS Collaboration
1
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Multiwavelenght observations of the previously unidentified blzar RX J0648.7+1516
We report on the VERITAS discovery of very high energy (VHE) gamma-ray emission above 200 GeV from the high-frequency-peaked BL Lac (HBL) object RX J0648.7+1516 (GB J0648+1516), associated with 1FGL J0648.8+1516. The photon spectrum above 200 GeV is fitted by a power law dN/dE = F-0(E/E-0)(-Gamma) with a photon index Gamma of 4.4 +/- 0.8(stat) +/- 0.3(syst) and a flux normalization F-0 of (2.3 +/- 0.5(stat) +/- 1.2(sys)) x 10(-11) TeV-1 cm(-2) s(-1) with E-0 = 300 GeV. No VHE variability is detected during VERITAS observations of RX J0648.7+1516 between 2010 March 4 and April 15. Following the VHE discovery, the optical identification and spectroscopic redshift were obtained using the Shane 3 m Telescope at the Lick Observatory, showing the unidentified object to be a BL Lac type with a redshift of z = 0.179. Broadband multiwavelength observations contemporaneous with the VERITAS exposure period can be used to subclassify the blazar as an HBL object, including data from the MDM observatory, Swift-UVOT, and X-Ray Telescope, and continuous monitoring at photon energies above 1 GeV from the Fermi Large Area Telescope (LAT). We find that in the absence of undetected, high-energy rapid variability, the one-zone synchrotron self-Compton (SSC) model overproduces the high-energy gamma-ray emission measured by the Fermi-LAT over 2.3 years. The spectral energy distribution can be parameterized satisfactorily with an external-Compton or lepto-hadronic model, which have two and six additional free parameters, respectively, compared to the one-zone SSC model.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/742/2/127
0004-637X
wos:2011-2013
127
WOS:000297211900067
Aliu, E (reprint author), Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA., afurniss@ucsc.edu; miki@ucolick.org; dpaneque@mppmu.mpg.de
US Department of Energy; NSERC in Canada; Science Foundation Ireland
(SFI ) [10/RFP/AST2748]; STFC in the UK; NASA [NNX10AF89G]; Fermi
[NNX09AU18G]; NSF [AST-0548180]; US National Science Foundation;
Smithsonian Institution
E. Aliu
T. Aune
M. Beilicke
W. Benbow
Markus Boettcher
A. Bouvier
S. M. Bradbury
J. H. Buckley
V. Bugaev
A. Cannon
A. Cesarini
L. Ciupik
M. P. Connolly
W. Cui
G. Decerprit
R. Dickherber
C. Duke
M. Errando
A. Falcone
Q. Feng
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
G. H. Gillanders
S. Godambe
S. Griffin
J. Grube
G. Gyuk
D. Hanna
B. Hivick
J. Holder
H. Huan
G. Hughes
C. M. Hui
T. B. Humensky
P. Kaaret
N. Karlsson
M. Kertzman
D. Kieda
H. Krawczynski
F. Krennrich
G. Maier
P. Majumdar
S. McArthur
A. McCann
P. Moriarty
R. Mukherjee
T. Nelson
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
A. Pichel
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
H. J. Rose
J. Ruppel
D. B. Saxon
G. H. Sembroski
C. Skole
A. W. Smith
D. Staszak
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
J. Tyler
A. Varlotta
V. V. Vassiliev
S. P. Wakely
T. C. Weekes
A. Weinstein
D. A. Williams
B. Zitzer
S. Ciprini
M. Fumagalli
K. Kaplan
D. Paneque
J. X. Prochaska
eng
uncontrolled
BL Lacertae objects: individual (RX J0648.7+1516, 1FGL J0648.8+1516, VER J0648+152)
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
36437
2011
2011
eng
10
1
743
article
IOP Publ. Ltd.
Bristol
1
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Veritas observations of gamma-ray bursts detected by swift
We present the results of 16 Swift-triggered Gamma-ray burst (GRB) follow-up observations taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) telescope array from 2007 January to 2009 June. The median energy threshold and response time of these observations were 260 GeV and 320 s, respectively. Observations had an average duration of 90 minutes. Each burst is analyzed independently in two modes: over the whole duration of the observations and again over a shorter timescale determined by the maximum VERITAS sensitivity to a burst with a t(-1.5) time profile. This temporal model is characteristic of GRB afterglows with high-energy, long-lived emission that have been detected by the Large Area Telescope on board the Fermi satellite. No significant very high energy (VHE) gamma-ray emission was detected and upper limits above the VERITAS threshold energy are calculated. The VERITAS upper limits are corrected for gamma-ray extinction by the extragalactic background light and interpreted in the context of the keV emission detected by Swift. For some bursts the VHE emission must have less power than the keV emission, placing constraints on inverse Compton models of VHE emission.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/743/1/62
0004-637X
wos:2011-2013
62
WOS:000297408300062
Aune, T (reprint author), Univ Calif Santa Cruz, Santa Cruz Inst Particle Phys, Santa Cruz, CA 95064 USA.
US Department of Energy; US National Science Foundation; Smithsonian
Institution; NSERC in Canada; Science Foundation Ireland [SFI
10/RFP/AST2748]; STFC in the UK; NASA [NNX09AR06G]
V. A. Acciari
E. Aliu
T. Arlen
T. Aune
M. Beilicke
W. Benbow
S. M. Bradbury
J. H. Buckley
V. Bugaev
K. Byrum
A. Cannon
A. Cesarini
J. L. Christiansen
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
C. Duke
M. Errando
A. Falcone
J. P. Finley
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
S. Godambe
S. Griffin
J. Grube
R. Guenette
G. Gyuk
D. Hanna
J. Holder
G. Hughes
C. M. Hui
T. B. Humensky
D. J. Jackson
P. Kaaret
N. Karlsson
M. Kertzman
D. Kieda
H. Krawczynski
F. Krennrich
M. J. Lang
A. S. Madhavan
G. Maier
S. McArthur
A. McCann
P. Moriarty
M. D. Newbold
R. A. Ong
M. Orr
A. N. Otte
N. Park
J. S. Perkins
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
H. J. Rose
J. Ruppel
D. B. Saxon
M. Schroedter
G. H. Sembroski
G. D. Sentuerk
A. W. Smith
D. Staszak
S. P. Swordy
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
A. Varlotta
V. V. Vassiliev
S. Vincent
M. Vivier
S. P. Wakely
J. E. Ward
T. C. Weekes
A. Weinstein
T. Weisgarber
D. A. Williams
M. Wood
eng
uncontrolled
astroparticle physics
eng
uncontrolled
gamma-ray burst: general
Institut für Physik und Astronomie
Referiert