38849
2015
2015
eng
26
578
article
EDP Sciences
Les Ulis
MAGIC Collaboration, VERITAS Collaboration
1
--
--
--
Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010
Context. Because of its proximity, Mrk 421 is one of the best sources on which to study the nature of BL Lac objects. Its proximity allows us to characterize its broadband spectral energy distribution (SED).
Aims. The goal is to better understand the mechanisms responsible for the broadband emission and the temporal evolution of Mrk 421. These mechanisms may also apply to more distant blazars that cannot be studied with the same level of detail.
Methods. A flare occurring in March 2010 was observed for 13 consecutive days (from MJD 55 265 to MJD 55 277) with unprecedented wavelength coverage from radio to very high energy (VHE; E > 100 GeV) gamma-rays with MAGIC, VERITAS, Whipple, Fermi-LAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We modeled the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigated the physical parameters, and evaluated whether the observed broadband SED variability can be associated with variations in the relativistic particle population.
Results. The activity of Mrk 421 initially was high and then slowly decreased during the 13-day period. The flux variability was remarkable at the X-ray and VHE bands, but it was minor or not significant at the other bands. The variability in optical polarization was also minor. These observations revealed an almost linear correlation between the X-ray flux at the 2-10 keV band and the VHE gamma-ray flux above 200 GeV, consistent with the gamma-rays being produced by inverse-Compton scattering in the Klein-Nishina regime in the framework of SSC models. The one-zone SSC model can describe the SED of each day for the 13 consecutive days reasonably well, which once more shows the success of this standard theoretical scenario to describe the SEDs of VHE BL Lacs such as Mrk 421. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission, while the other smaller zone, which is spatially separated from the first, contributes to the daily variable emission occurring at X-rays and VHE gamma-rays. The second blob is assumed to have a smaller volume and a narrow electron energy distribution with 3 x 10(4) < gamma < 6 x 10(5), where. is the Lorentz factor of the electrons. Such a two-zone scenario would naturally lead to the correlated variability at the X-ray and VHE bands without variability at the optical/UV band, as well as to shorter timescales for the variability at the X-ray and VHE bands with respect to the variability at the other bands.
Conclusions. Both the one-zone and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly with the underlying particle population. This shows that the particle acceleration and cooling mechanism that produces the radiating particles might be the main mechanism responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement with the observed SED at the narrow peaks of the low-and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by varying the parameters related to the emitting region itself (delta, B and R), in addition to the parameters related to the particle population.
Astronomy and astrophysics : an international weekly journal
10.1051/0004-6361/201424811
0004-6361
1432-0746
wos:2015
A22
WOS:000357502600034
Paneque, D (reprint author), Max Planck Inst Phys & Astrophys, D-80805 Munich, Germany., dpaneque@mpp.mpg.de; sysun@mpp.mpg.de; takami@post.kek.jp
German BMBF; German MPG; Italian INFN; Italian INAF; Swiss National Fund
SNF; ERDF under the Spanish MINECO; Japanese JSPS; Japanese MEXT; Centro
de Excelencia Severo Ochoa project of the Spanish Consolider-Ingenio
programme [SEV-2012-0234]; CPAN project of the Spanish
Consolider-Ingenio programme [CSD2007-00042]; MultiDark project of the
Spanish Consolider-Ingenio programme [CSD2009-00064]; Academy of Finland
[268740, 212656, 210338, 121148]; Croatian Science Foundation (HrZZ)
Project [09/176]; University of Rijeka [13.12.1.3.02]; DFG Collaborative
Research Centers [SFB823/C4, SFB876/C3]; Polish MNiSzW
[745/N-HESS-MAGIC/2010/0]; 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 UK; NASA
[NNX11AQ03G, NNX08AW31G, NNX11A043G]; Academia Sinica; NSF [AST-0808050,
AST-1109911]; Russian RFBR [12-02-00452]; St. Petersburg University
[6.0.163.2010, 6.38.71.2012]; Georgian National Science Foundation
[GNSF/ST07/4-180]; Shota Rustaveli National Science Foundation
[FR/577/6-320/13]
J. Aleksic
S. Ansoldi
L. A. Antonelli
P. Antoranz
A. Babic
P. Bangale
U. Barres de Almeida
J. A. Barrio
J. Becerra Gonzalez
W. Bednarek
E. Bernardini
B. Biasuzzi
A. Biland
O. Blanch Bigas
A. Boller
S. Bonnefoy
G. Bonnoli
F. Borracci
T. Bretz
E. Carmona
A. Carosi
P. Colin
E. Colombo
J. L. Contreras
J. Cortina
S. Covino
P. Da Vela
F. Dazzi
A. De Angelis
G. De Caneva
B. De Lotto
E. de Ona Wilhelmi
C. Delgado Mendez
Dijana Dominis Prester
D. Dorner
M. Doro
S. Einecke
D. Eisenacher
D. Elsaesser
M. V. Fonseca
L. Font
K. Frantzen
C. Fruck
D. Galindo
R. J. Garcia Lopez
M. Garczarczyk
D. Garrido Terrats
M. Gaug
N. Godinovic
A. Gonzalez Munoz
S. R. Gozzini
D. Hadasch
Y. Hanabata
M. Hayashida
J. Herrera
D. Hildebrand
J. Hose
D. Hrupec
G. Hughes
W. Idec
V. Kadenius
H. Kellermann
M. L. Knoetig
K. Kodani
Y. Konno
J. Krause
H. Kubo
J. Kushida
A. La Barbera
D. Lelas
N. Lewandowska
E. Lindfors
S. Lombardi
M. Lopez
R. Lopez-Coto
A. Lopez-Oramas
E. Lorenz
I. Lozano
M. Makariev
K. Mallot
G. Maneva
N. Mankuzhiyil
K. Mannheim
L. Maraschi
B. Marcote
M. Mariotti
M. Martinez
D. Mazin
U. Menzel
J. M. Miranda
R. Mirzoyan
A. Moralejo
P. Munar-Adrover
D. Nakajima
A. Niedzwiecki
K. Nilsson
K. Nishijima
K. Noda
R. Orito
A. Overkemping
S. Paiano
M. Palatiello
D. Paneque
R. Paoletti
J. M. Paredes
X. Paredes-Fortuny
M. Persic
P. G. Prada Moroni
E. Prandini
I. Puljak
R. Reinthal
W. Rhode
M. Ribo
J. Rico
J. Rodriguez Garcia
S. Rugamer
T. Saito
K. Saito
K. Satalecka
V. Scalzotto
V. Scapin
C. Schultz
T. Schweizer
S. Sun
S. N. Shore
A. Sillanpaa
J. Sitarek
I. Snidaric
D. Sobczynska
F. Spanier
V. Stamatescu
A. Stamerra
T. Steinbring
B. Steinke
J. Storz
M. Strzys
L. Takalo
H. Takami
F. Tavecchio
P. Temnikov
T. Terzic
D. Tescaro
M. Teshima
J. Thaele
O. Tibolla
D. F. Torres
T. Toyama
A. Treves
M. Uellenbeck
P. Vogler
R. Zanin
S. Archambault
A. Archer
M. Beilicke
W. Benbow
K. Berger
R. Bird
Jonathan Biteau
J. H. Buckley
V. Bugaev
M. Cerruti
Xiaoming Chen
L. Ciupik
E. Collins-Hughes
W. Cui
J. D. Eisch
A. Falcone
Q. Feng
J. P. Finley
P. Fortin
L. Fortson
A. Furniss
N. Galante
G. H. Gillanders
S. Griffin
G. Gyuk
Nils Hakansson
J. Holder
C. A. Johnson
P. Kaaret
P. Kar
M. Kertzman
D. Kieda
M. J. Lang
S. McArthur
A. McCann
K. Meagher
J. Millis
P. Moriarty
R. A. Ong
A. N. Otte
J. S. Perkins
A. Pichel
Manuela Pohl
A. Popkow
H. Prokoph
Elisa Pueschel
K. Ragan
L. C. Reyes
P. T. Reynolds
G. T. Richards
E. Roache
A. C. Rovero
G. H. Sembroski
K. Shahinyan
D. Staszak
Igor O. Telezhinsky
J. V. Tucci
J. Tyler
A. Varlotta
S. P. Wakely
R. Welsing
Alina Wilhelm
D. A. Williams
S. Buson
J. Finke
M. Villata
C. Raiteri
H. D. Aller
M. F. Aller
A. Cesarini
W. P. Chen
M. A. Gurwell
S. G. Jorstad
G. N. Kimeridze
E. Koptelova
O. M. Kurtanidze
S. O. Kurtanidze
A. Lahteenmaki
V. M. Larionov
E. G. Larionova
H. C. Lin
B. McBreen
J. W. Moody
D. A. Morozova
A. P. Marscher
W. Max-Moerbeck
M. G. Nikolashvili
M. Perri
A. C. S. Readhead
J. L. Richards
J. A. Ros
A. C. Sadun
T. Sakamoto
L. A. Sigua
P. S. Smith
M. Tornikoski
I. S. Troitsky
A. E. Wehrle
B. Jordan
eng
uncontrolled
radiation mechanisms: non-thermal
eng
uncontrolled
galaxies: active
eng
uncontrolled
BL Lacertae objects: individual: Mrk 421
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
37685
2014
2014
eng
9
2
790
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Very-high energy observations of the galactic center region by veritas IN 2010-2012
The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 GeV) gamma-ray observations. Potential sources of GeV/TeV gamma-ray emission have been suggested, e.g., the accretion of matter onto the supermassive black hole, cosmic rays from a nearby supernova remnant (e.g., Sgr A East), particle acceleration in a plerion, or the annihilation of dark matter particles. The Galactic center has been detected by EGRET and by Fermi/LAT in the MeV/GeV energy band. At TeV energies, the Galactic center was detected with moderate significance by the CANGAROO and Whipple 10 m telescopes and with high significance by H.E.S.S., MAGIC, and VERITAS. We present the results from three years of VERITAS observations conducted at large zenith angles resulting in a detection of the Galactic center on the level of 18 standard deviations at energies above similar to 2.5 TeV. The energy spectrum is derived and is found to be compatible with hadronic, leptonic, and hybrid emission models discussed in the literature. Future, more detailed measurements of the high-energy cutoff and better constraints on the high-energy flux variability will help to refine and/or disentangle the individual models.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/790/2/149
0004-637X
1538-4357
wos:2014
149
WOS:000339115800066
Archer, A (reprint author), Washington Univ, Dept Phys, St Louis, MO 63130 USA., beilicke@physics.wustl.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
A. Archer
Anna Barnacka
M. Beilicke
W. Benbow
K. Berger
R. Bird
Jonathan Biteau
J. H. Buckley
V. Bugaev
K. Byrum
J. V. Cardenzana
M. Cerruti
W. Chen
Xiaoming Chen
L. Ciupik
M. P. Connolly
W. Cui
H. J. Dickinson
J. Dumm
J. D. Eisch
A. Falcone
Simone Federici
Q. Feng
J. P. Finley
H. Fleischhack
L. Fortson
A. Furniss
N. Galante
S. Griffin
S. T. Griffiths
J. Grube
G. Gyuk
Nils Hakansson
D. Hanna
J. Holder
G. Hughes
C. A. Johnson
P. Kaaret
P. Kar
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
S. Kumar
M. J. Lang
G. Maier
S. McArthur
A. McCann
K. Meagher
P. Moriarty
R. Mukherjee
D. Nieto
R. A. Ong
A. N. Otte
N. Park
J. S. Perkins
Manuela 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
A. W. Smith
D. Staszak
Igor O. Telezhinsky
J. V. Tucci
J. Tyler
A. Varlotta
S. Vincent
S. P. Wakely
A. Weinstein
R. Welsing
Alina Wilhelm
D. A. Williams
A. Zajczyk
B. Zitzer
eng
uncontrolled
astroparticle physics
eng
uncontrolled
black hole physics
eng
uncontrolled
Galaxy: center
eng
uncontrolled
gamma rays: galaxies
eng
uncontrolled
methods: data analysis
eng
uncontrolled
radiation mechanisms: non-thermal
Institut für Physik und Astronomie
Referiert
37289
2014
2014
eng
11
2
797
article
IOP Publ. Ltd.
Bristol
Veritas Collaboration
1
--
--
--
Investigating broadband variability of the TeV blazar 1ES 1959+650
We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift Ultraviolet and Optical Telescope, X-ray observations by the Swift X-ray Telescope, high-energy gamma-ray observations with the Fermi Large Area Telescope, and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 2012 April 17 and 2012 June 1 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected by a nearby cloud of gas, allowing the reflected emission to re-enter the blob and produce an elevated gamma-ray state with no simultaneous elevated synchrotron flux. The model applied here, although not required to explain the observed variability pattern, represents one possible scenario which can describe the observations. As applied to an elevated VHE state of 66% of the Crab Nebula flux, observed on a single night during the observation period, the reflected emission scenario does not support a purely leptonic non-thermal emission mechanism. The reflected emission model does, however, predict a reflected photon field with sufficient energy to enable elevated gamma-ray emission via pion production with protons of energies between 10 and 100 TeV.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/797/2/89
0004-637X
1538-4357
wos:2014
89
WOS:000346291600017
Aliu, E (reprint author), Columbia Univ, Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA., amy.furniss@gmail.com; Markus.Bottcher@nwu.ac.za
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
Anna Barnacka
M. Beilicke
W. Benbow
K. Berger
R. Bird
A. Bouvier
J. H. Buckley
V. Bugaev
M. Cerruti
X. Chen
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
J. Dumm
J. D. Eisch
A. Falcone
S. Federici
Q. Feng
J. P. Finley
H. Fleischhack
P. Fortin
L. Fortson
A. Furniss
N. Galante
G. H. Gillanders
S. Griffin
S. T. Griffiths
J. Grube
G. Gyuk
N. Hakansson
D. Hanna
J. Holder
G. Hughes
Z. Hughes
T. B. Humensky
C. A. Johnson
P. Kaaret
P. Kar
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
M. J. Lang
A. S. Madhavan
P. Majumdar
S. McArthur
A. McCann
K. Meagher
J. Millis
P. Moriarty
R. Mukherjee
T. Nelson
D. Nieto
R. A. Ong
A. N. Otte
N. Park
J. S. Perkins
M. Pohl
A. Popkow
H. Prokoph
J. Quinn
K. Ragan
J. Rajotte
L. C. Reyes
P. T. Reynolds
G. T. Richards
E. Roache
A. Sadun
M. Santander
G. H. Sembroski
K. Shahinyan
F. Sheidaei
A. W. Smith
D. Staszak
Igor O. Telezhinsky
M. Theiling
J. Tyler
A. Varlotta
V. V. Vassiliev
S. Vincent
S. P. Wakely
T. C. Weekes
A. Weinstein
R. Welsing
Alina Wilhelm
D. A. Williams
B. Zitzer
Markus Boettcher
M. Fumagalli
eng
uncontrolled
BL Lacertae objects: individual (1ES 1959+650)
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
45283
2016
2016
eng
19
151
article
IOP Publ. Ltd.
Bristol
VERITAS Collaboration
1
--
--
--
UPPER LIMITS FROM FIVE YEARS OF BLAZAR OBSERVATIONS WITH THE VERITAS CHERENKOV TELESCOPES
Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E > 100 GeV) gamma-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of similar to 570 hr. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog that are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have spectroscopic distance estimates. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample, we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data set, which shows a 4s excess.
The astronomical journal
10.3847/0004-6256/151/6/142
0004-6256
1538-3881
wos2016:2019
142
WOS:000377990300009
Benbow, W (reprint author), Harvard Smithsonian Ctr Astrophys, Fred Lawrence Whipple Observ, Amado, AZ 85645 USA., wystan.benbow@cfa.harvard.edu; matteo.cerruti@lpnhe.in2p3.fr; caajohns@ucsc.edu
U.S. Department of Energy Office of Science; U.S. National Science Foundation; Smithsonian Institution; NSERC in Canada; Science and Technology Facilities Council [ST/L00075X/1]
importub
2020-03-22T17:15:01+00:00
filename=package.tar
33e112e5f9e5ea910d59c04eb1e45e3e
S. Archambault
A. Archer
W. Benbow
R. Bird
Jonathan Biteau
M. Buchovecky
J. H. Buckley
V. Bugaev
K. Byrum
M. Cerruti
Xuhui Chen
L. Ciupik
M. P. Connolly
W. Cui
J. D. Eisch
M. Errando
A. Falcone
Q. Feng
J. P. Finley
H. Fleischhack
P. Fortin
L. Fortson
A. Furniss
G. H. Gillanders
S. Griffin
J. Grube
G. Gyuk
M. Huetten
Nils Hakansson
D. Hanna
J. Holder
T. B. Humensky
C. A. Johnson
P. Kaaret
P. Kar
N. Kelley-Hoskins
M. Kertzman
D. Kieda
M. Krause
F. Krennrich
S. Kumar
M. J. Lang
G. Maier
S. McArthur
A. McCann
K. Meagher
P. Moriarty
R. Mukherjee
T. Nguyen
D. Nieto
R. A. Ong
A. N. Otte
N. Park
J. S. Perkins
A. Pichel
Martin Pohl
A. Popkow
Elisa Pueschel
J. Quinn
K. Ragan
P. T. Reynolds
G. T. Richards
E. Roache
A. C. Rovero
M. Santander
G. H. Sembroski
K. Shahinyan
A. W. Smith
D. Staszak
Igor O. Telezhinsky
J. V. Tucci
J. Tyler
S. Vincent
S. P. Wakely
O. M. Weiner
A. Weinstein
D. A. Williams
B. Zitzer
M. Fumagalli
J. X. Prochaska
eng
uncontrolled
BL Lacertae objects: general
eng
uncontrolled
galaxies: active
eng
uncontrolled
gamma rays: galaxies
eng
uncontrolled
radiation mechanisms: non-thermal
Institut für Physik und Astronomie
Referiert
Import
44871
2016
2016
eng
12
594
article
EDP Sciences
Les Ulis
Veritas Collaboration
1
--
--
--
Very high energy outburst of Markarian 501 in May 2009
The very high energy (VHE; E > 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54 938-54 956), 2009, as part of an extensive multiwavelength campaign from radio to VHE. Strong VHE yray activity was detected on May 1st with Whipple and VERITAS, when the flux (E > 400 GeV) increased to 10 times the preflare baseline flux (3.9 x 10(-11) ph cm(-2) s(-1)), reaching five times the flux of the Crab Nebula. This coincided with a decrease in the optical polarization and a rotation of the polarization angle by 15. This VHE flare showed a fast flux variation with an increase of a factor similar to 4 in 25 min, and a falling time of similar to 50 min. We present the observations of the quiescent state previous to the flare and of the high state after the flare, focusing on the flux and spectral variability from Whipple, VERITAS, Fermi-LAT, RXTE, and Swift combined with optical and radio data.
Physical chemistry, chemical physics : a journal of European Chemical Societies
10.1051/0004-6361/201628744
1432-0746
wos2016:2019
A76
WOS:000385832200085
Pichel, A (reprint author), Inst Astron & Fis Espacio, Casilla Correo 67,Sucursal 28,C1428ZAA, Buenos Aires, DF, Argentina., anapichel@iafe.uba.ar
US Department of Energy Office of Science; US National Science Foundation; Smithsonian Institution; NSERC in Canada; South African Research Chairs Initiative (SARChI) by National Research Foundation; Department of Science and Technology of South Africa
importub
2020-03-22T13:48:01+00:00
filename=package.tar
9eac71db8d99b6f78ad5d64f40931fa9
E. Aliu
S. Archambault
A. Archer
T. Arlen
T. Aune
Anna Barnacka
B. Behera
M. Beilicke
W. Benbow
K. Berger
R. Bird
Markus Böttcher
A. Bouvier
M. Buchovecky
J. H. Buckley
V. Bugaev
J. V. Cardenzana
M. Cerruti
A. Cesarini
Xuhui Chen
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
J. Dumm
J. D. Eisch
A. Falcone
Simone Federici
Q. Feng
J. P. Finley
H. Fleischhack
P. Fortin
L. Fortson
A. Furniss
N. Galante
D. Gall
G. H. Gillanders
S. Griffin
S. T. Griffiths
J. Grube
G. Gyuk
M. Hütten
Nils Hakansson
J. Holder
G. Hughes
T. B. Humensky
C. A. Johnson
P. Kaaret
P. Kar
N. Kelley-Hoskins
M. Kertzman
Y. Khassen
D. Kieda
M. Krause
H. Krawczynski
F. Krennrich
M. J. Lang
A. S. Madhavan
G. Maier
S. McArthur
A. McCann
K. Meagher
J. Millis
P. Moriarty
R. Mukherjee
D. Nieto
R. A. Ong
M. Orr
A. N. Otte
D. Pandel
N. Park
V. Pelassa
J. S. Perkins
A. Pichel
Martin Pohl
A. Popkow
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
J. Rousselle
A. C. Rovero
D. B. Saxon
G. H. Sembroski
K. Shahinyan
F. Sheidaei
C. Skole
A. W. Smith
D. Staszak
Igor O. Telezhinsky
M. Theiling
N. W. Todd
J. V. Tucci
J. Tyler
A. Varlotta
V. V. Vassiliev
S. Vincent
S. P. Wakely
O. M. Weiner
A. Weinstein
R. Welsing
Alina Wilhelm
D. A. Williams
B. Zitzer
M. G. Baring
J. Becerra Gonzalez
A. N. Cillis
D. Horan
D. Paneque
eng
uncontrolled
BL Lacertae objects: individual: Mrk 501
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
Import
34657
2013
2013
eng
10
2
776
article
IOP Publ. Ltd.
Bristol
VERITAS Collaboration
1
--
--
--
Discovery of a new tev Gamma-Ray source - VER J0521+211
We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov Telescope Array. These observations were motivated by the discovery of a cluster of >30 GeV photons in the first year of Fermi Large Area Telescope observations. VER J0521+211 is relatively bright at TeV energies, with a mean photon flux of (1.93 +/- 0.13(stat) +/- 0.78(sys)) x 10(-11) cm(-2) s(-1) above 0.2 TeV during the period of the VERITAS observations. The source is strongly variable on a daily timescale across all wavebands, from optical to TeV, with a peak flux corresponding to similar to 0.3 times the steady Crab Nebula flux at TeV energies. Follow-up observations in the optical and X-ray bands classify the newly discovered TeV source as a BL Lac-type blazar with uncertain redshift, although recent measurements suggest z = 0.108. VER J0521+211 exhibits all the defining properties of blazars in radio, optical, X-ray, and gamma-ray wavelengths.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/776/2/69
0004-637X
1538-4357
wos:2011-2013
69
WOS:000327216100006
Archambault, S (reprint author), McGill Univ, Dept Phys, 3600 Univ St, Montreal, PQ H3A 2T8, Canada., errando@astro.columbia.edu; jholder@physics.udel.edu; sfegan@llr.in2p3.fr; fortin@veritas.sao.arizona.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; INAF in Italy; CNES in
France; NASA [NNX10AP66G, NNX12AJ30G, NNX10AF89G]; Russian Foundation
for Basic Research [11-02-00368, 12-02-33101]; Russian Academy of
Sciences; Dynasty Foundation; South African Department of Science and
Technology through the National Research Foundation under NRF SARChI
Chair [64789]; NASA-Fermi [NNX08AV67G, 11-Fermi11-0019, NNX09AU10G]
S. Archambault
T. Arlen
T. Aune
B. Behera
M. Beilicke
W. Benbow
R. Bird
A. Bouvier
J. H. Buckley
V. Bugaev
K. Byrum
A. Cesarini
L. Ciupik
M. P. Connolly
W. Cui
M. Errando
A. Falcone
Simone Federici
Q. Feng
J. P. Finley
L. Fortson
A. Furniss
N. Galante
D. Gall
G. H. Gillanders
S. Griffin
J. Grube
G. Gyuk
D. Hanna
J. Holder
G. Hughes
T. B. Humensky
P. Kaaret
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
S. Kumar
M. J. Lang
A. S. Madhavan
G. Maier
P. Majumdar
S. McArthur
A. McCann
J. Millis
P. Moriarty
R. Mukherjee
A. O'Faolain de Bhroithe
R. A. Ong
A. N. Otte
N. Park
J. S. Perkins
Martin Pohl
A. Popkow
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
G. T. Richards
E. Roache
D. B. Saxon
G. H. Sembroski
A. W. Smith
D. Staszak
Igor O. Telezhinsky
M. Theiling
A. Varlotta
V. V. Vassiliev
S. Vincent
S. P. Wakely
T. C. Weekes
A. Weinstein
R. Welsing
D. A. Williams
B. Zitzer
Markus Boettcher
S. J. Fegan
P. Fortin
J. P. Halpern
Y. Y. Kovalev
M. L. Lister
J. Liu
A. B. Pushkarev
P. S. Smith
eng
uncontrolled
BL Lacertae objects: individual (VER J0521+211)
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
34727
2013
2013
eng
8
1
775
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Multiwavelenght observations and modeling of 1ES 1959+650 in a low flux state
We report on the VERITAS observations of the high-frequency peaked BL Lac object 1ES 1959+650 in the period 2007-2011. This source is detected at TeV energies by VERITAS at 16.4 standard deviation (sigma) significance in 7.6 hr of observation in a low flux state. A multiwavelength spectral energy distribution (SED) is constructed from contemporaneous data from VERITAS, Fermi-LAT, RXTE PCA, and Swift UVOT. Swift XRT data is not included in the SED due to a lack of simultaneous observations with VERITAS. In contrast to the orphan gamma-ray flare exhibited by this source in 2002, the X-ray flux of the source is found to vary by an order of magnitude, while other energy regimes exhibit less variable emission. A quasi-equilibrium synchrotron self-Compton model with an additional external radiation field is used to describe three SEDs corresponding to the lowest, highest, and average X-ray states. The variation in the X-ray spectrum is modeled by changing the electron injection spectral index, with minor adjustments of the kinetic luminosity in electrons. This scenario produces small-scale flux variability of the order of less than or similar to 2 in the high energy (E > 1MeV) and very high energy (E > 100 GeV) gamma-ray regimes, which is corroborated by the Fermi-LAT, VERITAS, and Whipple 10 m telescope light curves.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/775/1/3
0004-637X
wos:2011-2013
3
WOS:000324615800003
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; NARC'S in Canada; Science
Foundation Ireland [SFI 10/RFP/AST2748]; STFC in the U.K.; Irish
Research Council "Embark Initiative"
E. Aliu
S. Archambault
T. Arlen
T. Aune
M. Beilicke
W. Benbow
R. Bird
Markus Boettcher
A. Bouvier
V. Bugaev
K. Byrum
A. Cesarini
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
R. Dickherber
C. Duke
J. Dumm
M. Errando
A. Falcone
Simone Federici
Q. Feng
J. P. Finley
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
G. H. Gillanders
S. Griffin
J. Grube
G. Gyuk
D. Hanna
J. Holder
G. Hughes
T. B. Humensky
P. Kaaret
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
M. J. Lang
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
A. Pichel
Martin Pohl
A. Popkow
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
D. B. Saxon
M. Schroedter
G. H. Sembroski
C. Skole
A. W. Smith
D. Staszak
Igor O. Telezhinsky
M. Theiling
J. Tyler
A. Varlotta
V. V. Vassiliev
S. P. Wakely
T. C. Weekes
A. Weinstein
R. Welsing
D. A. Williams
B. Zitzer
eng
uncontrolled
BL Lacertae objects: general
eng
uncontrolled
BL Lacertae objects: individual (1ES 1959+650=VER J1959+651)
eng
uncontrolled
galaxies: active
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
35904
2012
2012
eng
6
2
750
article
IOP Publ. Ltd.
Bristol
1
--
--
--
Disovery of high-energy and very high energy gamma-ray emission from the blazar RBS 0413
We report on the discovery of high-energy (HE; E > 0.1 GeV) and very high energy (VHE; E > 100 GeV) gamma-ray emission from the high-frequency-peaked BL Lac object RBS 0413. VERITAS, a ground-based gamma-ray observatory, detected VHE. rays from RBS 0413 with a statistical significance of 5.5 standard deviations (sigma) and a gamma-ray flux of (1.5 +/- 0.6(stat) +/- 0.7(syst)) x 10(-8) photons m(-2) s(-1) (similar to 1% of the Crab Nebula flux) above 250 GeV. The observed spectrum can be described by a power law with a photon index of 3.18 +/- 0.68(stat) +/- 0.30(syst). Contemporaneous observations with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope detected HE gamma rays from RBS 0413 with a (stat)istical significance of more than 9 sigma, a power-law photon index of 1.57 +/- 0.12(stat-0.12sys')(+0.11) and a gamma-ray flux between 300 MeV and 300 GeV of (1.64 +/- 0.43(stat-0.22sys)(+ 0.31)) x 10(-5) photons m(-2) s(-1). We present the results from Fermi-LAT and VERITAS, including a spectral energy distribution modeling of the gamma-ray, quasi-simultaneous X-ray (Swift-XRT), ultraviolet (Swift-UVOT), and R-band optical (MDM) data. We find that, if conditions close to equipartition are required, both the combined synchrotron self-Compton/external-Compton and the lepto-hadronic models are preferred over a pure synchrotron self-Compton model.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/750/2/94
0004-637X
wos:2011-2013
94
WOS:000303446500008
Aliu, E (reprint author), Columbia Univ, Dept Phys & Astron, Barnard Coll, New York, NY 10027 USA., gunessenturk@gmail.com; fortin@llr.in2p3.fr; deirdre@llr.in2p3.fr
US Department of Energy Office of Science; US National Science
Foundation; Smithsonian Institution; NASA; NSERC in Canada; Science
Foundation Ireland [SFI 10/RFP/AST2748]; STFC in the UK
E. Aliu
S. Archambault
T. Arlen
T. Aune
M. Beilicke
W. Benbow
Markus Boettcher
A. Bouvier
S. M. Bradbury
J. H. Buckley
V. Bugaev
K. Byrum
A. Cannon
A. Cesarini
L. Ciupik
E. Collins-Hughes
M. P. Connolly
P. Coppi
W. Cui
G. Decerprit
R. Dickherber
J. Dumm
Manel Errando
A. Falcone
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
K. Hawkins
J. Holder
H. Huan
G. Hughes
T. B. Humensky
P. Kaaret
N. Karlsson
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
M. J. Lang
K. Lee
A. S. Madhavan
G. Maier
P. Majumdar
S. McArthur
A. McCann
P. Moriarty
Reshmi Mukherjee
R. A. Ong
M. Orr
A. N. Otte
N. Palma
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
A. W. Smith
D. Staszak
Igor O. Telezhinsky
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
A. Varlotta
M. Vivier
S. P. Wakely
J. E. Ward
T. C. Weekes
A. Weinstein
T. Weisgarber
D. A. Williams
B. Zitzer
P. Fortin
D. Horan
eng
uncontrolled
BL Lacertae objects: individual (RBS 0413-VER J0319+187)
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
35269
2013
2013
eng
13
2
762
article
IOP Publ. Ltd.
Bristol
VERITAS Collaboration
1
--
--
--
Rapid TeV Gamma-Ray flaring of bl lacertae
We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6 minute exposure, when the integral flux above 200 GeV reached (3.4 +/- 0.6) x 10(-6) photons m(-2) s(-1), roughly 125% of the Crab Nebula flux measured by VERITAS. The light curve indicates that the observations missed the rising phase of the flare but covered a significant portion of the decaying phase. The exponential decay time was determined to be 13 +/- 4 minutes, making it one of the most rapid gamma-ray flares seen from a TeV blazar. The gamma-ray spectrum of BL Lacertae during the flare was soft, with a photon index of 3.6 +/- 0.4, which is in agreement with the measurement made previously by MAGIC in a lower flaring state. Contemporaneous radio observations of the source with the Very Long Baseline Array revealed the emergence of a new, superluminal component from the core around the time of the TeV gamma-ray flare, accompanied by changes in the optical polarization angle. Changes in flux also appear to have occurred at optical, UV, and GeV gamma-ray wavelengths at the time of the flare, although they are difficult to quantify precisely due to sparse coverage. A strong flare was seen at radio wavelengths roughly four months later, which might be related to the gamma-ray flaring activities. We discuss the implications of these multiwavelength results.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/762/2/92
0004-637X
wos:2011-2013
92
WOS:000313008900026
Arlen, T (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA., cui@purdue.edu; qfeng@purdue.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; NASA [NNX08AV65G,
NNX08AV61G, NNX09AT99G, NNX11AQ03G, NNX08AW31G, NNX11A043G, NNX08AV67G];
NSF [AST-0907893, AST-0808050, AST-1109911]; Russian Foundation for
Basic Research [11-02-00368, 12-02-33101]; Physical Sciences Division of
the Russian Academy of Sciences; Dynasty Foundation; Academia Sinica;
Fermi Guest Investigator grants [NNX08AW56G, NNX09AU10G]; Academy of
Finland [212656, 210338, 121148]
T. Arlen
T. Aune
M. Beilicke
W. Benbow
A. Bouvier
J. H. Buckley
V. Bugaev
A. Cesarini
L. Ciupik
M. P. Connolly
W. Cui
R. Dickherber
J. Dumm
M. Errando
A. Falcone
S. Federici
Q. Feng
J. P. Finley
G. Finnegan
L. Fortson
A. Furniss
N. Galante
D. Gall
S. Griffin
J. Grube
G. Gyuk
D. Hanna
J. Holder
T. B. Humensky
P. Kaaret
N. Karlsson
M. Kertzman
Y. Khassen
D. Kieda
H. Krawczynski
F. Krennrich
G. Maier
P. Moriarty
R. Mukherjee
T. Nelson
A. O'Faolain de Bhroithe
R. A. Ong
M. Orr
N. Park
J. S. Perkins
A. Pichel
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
D. B. Saxon
M. Schroedter
G. H. Sembroski
D. Staszak
Igor O. Telezhinsky
G. Tesic
M. Theiling
K. Tsurusaki
A. Varlotta
S. Vincent
S. P. Wakely
T. C. Weekes
A. Weinstein
R. Welsing
D. A. Williams
B. Zitzer
S. G. Jorstad
N. R. MacDonald
A. P. Marscher
P. S. Smith
R. C. Walker
T. Hovatta
J. Richards
W. Max-Moerbeck
A. Readhead
M. L. Lister
Y. Y. Kovalev
A. B. Pushkarev
M. A. Gurwell
A. Lahteenmaki
E. Nieppola
M. Tornikoski
E. Jarvela
eng
uncontrolled
galaxies: active
eng
uncontrolled
galaxies: individual (BL Lacertae, VER J2202+422)
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert
35522
2012
2012
eng
13
2
759
article
IOP Publ. Ltd.
Bristol
VERITAS Collaboration
1
--
--
--
Veritas observations of six bright, hard-spectrum fermi-lat blazars
We report on VERITAS very high energy (VHE; E >= 100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band, taking gamma-ray absorption by the extragalactic background light into account. This allowed the selection of six bright, hard-spectrum blazars that were good candidate TeV emitters. Spectroscopic redshift measurements were attempted with the Keck Telescope for the targets without Sloan Digital Sky Survey spectroscopic data. No VHE emission is detected during the observations of the six sources described here. Corresponding TeV upper limits are presented, along with contemporaneous Fermi observations and non-concurrent Swift UVOT and X-Ray Telescope data. The blazar broadband spectral energy distributions (SEDs) are assembled and modeled with a single-zone synchrotron self-Compton model. The SED built for each of the six blazars shows a synchrotron peak bordering between the intermediate-and high-spectrum-peak classifications, with four of the six resulting in particle-dominated emission regions.
The astrophysical journal : an international review of spectroscopy and astronomical physics
10.1088/0004-637X/759/2/102
0004-637X
wos:2011-2013
102
WOS:000310911300025
Furniss, A (reprint author), Univ Calif Santa Cruz, Santa Cruz Inst Particle Phys, Santa Cruz, CA 95064 USA., afurniss@ucsc.edu; pafortin@cfa.harvard.edu; deirdre@llr.in2p3.fr
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; NSF [AST-0548180]; Alfred
P. Sloan Foundation; U.S. Department of Energy; National Aeronautics and
Space Administration; Japanese Monbukagakusho; Max Planck Society;
Higher Education Funding Council for England; Istituto Nazionale di
Astrofisica in Italy; Centre National d'Etudes Spatiales in France
E. Aliu
S. Archambault
T. Arlen
T. Aune
M. Beilicke
W. Benbow
Markus Boettcher
A. Bouvier
J. H. Buckley
V. Bugaev
A. Cesarini
L. Ciupik
E. Collins-Hughes
M. P. Connolly
W. Cui
R. Dickherber
C. Duke
J. Dumm
M. Errando
A. Falcone
Simone 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
P. Kaaret
N. Karlsson
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
A. Pichel
Martin Pohl
H. Prokoph
J. Quinn
K. Ragan
L. C. Reyes
P. T. Reynolds
E. Roache
D. B. Saxon
G. H. Sembroski
D. Staszak
Igor O. Telezhinsky
G. Tesic
M. Theiling
S. Thibadeau
K. Tsurusaki
A. Varlotta
V. V. Vassiliev
S. Vincent
M. Vivier
S. P. Wakely
T. C. Weekes
A. Weinstein
R. Welsing
D. A. Williams
B. Zitzer
P. Fortin
D. Horan
M. Fumagalli
K. Kaplan
J. X. Prochaska
eng
uncontrolled
BL Lacertae objects: general
eng
uncontrolled
gamma rays: galaxies
Institut für Physik und Astronomie
Referiert