TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Arlen, T.
A1 - Aune, T.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bouvier, A.
A1 - Bradbury, S. M.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cannon, A.
A1 - Cesarini, A.
A1 - Christiansen, J. L.
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Decerprit, G.
A1 - Dickherber, R.
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Feng, Q.
A1 - Ferrer, F.
A1 - Finley, J. P.
A1 - Finnegan, G.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gall, D.
A1 - Godambe, S.
A1 - Griffin, S.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Huan, H.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Karlsson, N.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Lee, K.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Ong, R. A.
A1 - Orr, M.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Martin
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Roache, E.
A1 - Rose, H. J.
A1 - Ruppel, J.
A1 - Saxon, D. B.
A1 - Schroedter, M.
A1 - Sembroski, G. H.
A1 - Sentuerk, G. D.
A1 - Skole, C.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tesic, G.
A1 - Theiling, M.
A1 - Thibadeau, S.
A1 - Tsurusaki, K.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Vivier, M.
A1 - Wagner, R. G.
A1 - Wakely, S. P.
A1 - Ward, J. E.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Weisgarber, T.
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - VERITAS deep observations of the dwarf spheroidal galaxy Segue 1
JF - Physical review : D, Particles, fields, gravitation, and cosmology
N2 - 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 (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.
Y1 - 2012
U6 - http://dx.doi.org/10.1103/PhysRevD.85.062001
SN - 1550-7998 (print)
VL - 85
IS - 6
PB - American Physical Society
CY - College Park
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Arlen, T.
A1 - Aune, T.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Boettcher, M.
A1 - Bouvier, A.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Cesarini, A.
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickherber, R.
A1 - Duke, C.
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Finnegan, G.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gall, D.
A1 - Godambe, S.
A1 - Griffin, S.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Huan, H.
A1 - Kaaret, P.
A1 - Karlsson, N.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Lee, K.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nelson, T.
A1 - de Bhroithe, A. O'Faolain
A1 - Ong, R. A.
A1 - Orr, M.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pichel, A.
A1 - Pohl, Martin
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Roache, E.
A1 - Saxon, D. B.
A1 - Sembroski, G. H.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tesic, G.
A1 - Theiling, M.
A1 - Thibadeau, S.
A1 - Tsurusaki, K.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Vivier, M.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
A1 - Fortin, P.
A1 - Horan, D.
A1 - Fumagalli, M.
A1 - Kaplan, K.
A1 - Prochaska, J. X.
T1 - Veritas observations of six bright, hard-spectrum fermi-lat blazars
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - 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.
KW - BL Lacertae objects: general
KW - gamma rays: galaxies
Y1 - 2012
U6 - http://dx.doi.org/10.1088/0004-637X/759/2/102
SN - 0004-637X (print)
VL - 759
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - tAliu, E.
A1 - Archambault, S.
A1 - Arlen, T.
A1 - Aune, T.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Bouvier, A.
A1 - Bradbury, S. M.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cannon, A.
A1 - Cesarini, A.
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickherber, R.
A1 - Duke, C.
A1 - Dumm, J.
A1 - Dwarkadas, V. V.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Finnegan, G.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gall, D.
A1 - Gillanders, G. H.
A1 - Godambe, S.
A1 - Gotthelf, E. V.
A1 - Griffin, S.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Huan, H.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Karlsson, N.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Lang, M. J.
A1 - Lee, K.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nelson, T.
A1 - de Bhroithe, A. O'Faolain
A1 - Ong, R. A.
A1 - Orr, M.
A1 - Otte, A. N.
A1 - Pandel, D.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Roache, E.
A1 - Rose, H. J.
A1 - Ruppel, Jens
A1 - Saxon, D. B.
A1 - Schroedter, M.
A1 - Sembroski, G. H.
A1 - Sentuerk, G. D.
A1 - Skole, C.
A1 - Telezhinsky, Igor
A1 - Tesic, G.
A1 - Theiling, M.
A1 - Thibadeau, S.
A1 - Tsurusaki, K.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Ward, J. E.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Weisgarber, T.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - Discovery of TeV Gamma-Ray emission toward supernova remnant SNR G78.2+2.1
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We report the discovery of an unidentified, extended source of very-high-energy gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hr of data taken by the VERITAS gamma-ray observatory in 2009. These data confirm the preliminary indications of gamma-ray emission previously seen in a two-year (2007-2009) blind survey of the Cygnus region by VERITAS. VER J2019+407, which is detected at a post-trials significance of 7.5 standard deviations in the 2009 data, is localized to the northwestern rim of the remnant in a region of enhanced radio and X-ray emission. It has an intrinsic extent of 0 degrees.23 +/- 0 degrees.03(stat-0 degrees.02sys)(+0 degrees.04) and its spectrum is well-characterized by a differential power law (dN/dE = N-0 x (E/TeV)-Gamma) with a photon index of Gamma = 2.37 +/- 0.14(stat) +/- 0.20(sys) and a flux normalization of N-0 = 1.5 +/- 0.2(stat) +/- 0.4(sys) x 10(-12) photon TeV-1 cm(-2) s(-1). This yields an integral flux of 5.2 +/- 0.8(stat) +/- 1.4(sys) x 10(-12) photon cm(-2) s(-1) above 320 GeV, corresponding to 3.7% of the Crab Nebula flux. We consider the relationship of the TeV gamma-ray emission with the GeV gamma-ray emission seen from SNR G78.2+2.1 as well as that seen from a nearby cocoon of freshly accelerated cosmic rays. Multiple scenarios are considered as possible origins for the TeV gamma-ray emission, including hadronic particle acceleration at the SNR shock.
KW - acceleration of particles
KW - cosmic rays
KW - gamma rays: general
KW - ISM: supernova remnants
Y1 - 2013
U6 - http://dx.doi.org/10.1088/0004-637X/770/2/93
SN - 0004-637X (print)
VL - 770
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Behera, B.
A1 - Berger, K.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Bouvier, A.
A1 - Bugaev, V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dumm, J.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Lang, M. J.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - de Bhroithe, A. O'Faolain
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Ratliff, G.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Sheidaei, F.
A1 - Skole, C.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Zajczyk, A.
A1 - Zitzer, B.
T1 - Multiwavelemght oservatons of the TeV binary LS I+61 degrees 303 with veritas, fermi-lat, and swift/XRT during a TeV outburst
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We present the results of a multiwavelength observational campaign on the TeV binary system LS I +61 degrees 303 with the VERITAS telescope array (>200 GeV), Fermi-LAT (0.3-300 GeV), and Swift/XRT (2-10 keV). The data were taken from 2011 December through 2012 January and show a strong detection in all three wavebands. During this period VERITAS obtained 24.9 hr of quality selected livetime data in which LS I +61 degrees 303 was detected at a statistical significance of 11.9 sigma. These TeV observations show evidence for nightly variability in the TeV regime at a post-trial significance of 3.6 sigma. The combination of the simultaneously obtained TeV and X-ray fluxes do not demonstrate any evidence for a correlation between emission in the two bands. For the first time since the launch of the Fermi satellite in 2008, this TeV detection allows the construction of a detailed MeV-TeV spectral energy distribution from LS I +61 degrees 303. This spectrum shows a distinct cutoff in emission near 4 GeV, with emission seen by the VERITAS observations following a simple power-law above 200 GeV. This feature in the spectrum of LS I +61 degrees 303, obtained from overlapping observations with Fermi-LAT and VERITAS, may indicate that there are two distinct populations of accelerated particles producing the GeV and TeV emission.
KW - acceleration of particles
KW - binaries: general
KW - gamma rays: stars
KW - relativistic processes
KW - X-rays: binaries
Y1 - 2013
U6 - http://dx.doi.org/10.1088/0004-637X/779/1/88
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 779
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Arlen, T.
A1 - Aune, T.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Boettcher, M.
A1 - Bouvier, A.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cesarini, A.
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickherber, R.
A1 - Duke, C.
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Finnegan, G.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gall, D.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nelson, T.
A1 - de Bhroithe, A. O'Faolain
A1 - Ong, R. A.
A1 - Orr, M.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pichel, A.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Roache, E.
A1 - Saxon, D. B.
A1 - Schroedter, M.
A1 - Sembroski, G. H.
A1 - Skole, C.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Theiling, M.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - Multiwavelenght observations and modeling of 1ES 1959+650 in a low flux state
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - 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.
KW - BL Lacertae objects: general
KW - BL Lacertae objects: individual (1ES 1959+650=VER J1959+651)
KW - galaxies: active
KW - gamma rays: galaxies
Y1 - 2013
U6 - http://dx.doi.org/10.1088/0004-637X/775/1/3
SN - 0004-637X (print)
VL - 775
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Archambault, S.
A1 - Arlen, T.
A1 - Aune, T.
A1 - Behera, B.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Bouvier, A.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cesarini, A.
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gall, D.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - de Bhroithe, A. O'Faolain
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Saxon, D. B.
A1 - Sembroski, G. H.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Theiling, M.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
A1 - Boettcher, M.
A1 - Fegan, S. J.
A1 - Fortin, P.
A1 - Halpern, J. P.
A1 - Kovalev, Y. Y.
A1 - Lister, M. L.
A1 - Liu, J.
A1 - Pushkarev, A. B.
A1 - Smith, P. S.
T1 - Discovery of a new tev Gamma-Ray source - VER J0521+211
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - 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.
KW - BL Lacertae objects: individual (VER J0521+211)
KW - gamma rays: galaxies
Y1 - 2013
U6 - http://dx.doi.org/10.1088/0004-637X/776/2/69
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 776
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Archambault, S.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Bouvier, A.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Duke, C.
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - de Bhroithe, A. O'Faolain
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Pandel, D.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Sheidaei, F.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Theiling, M.
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Williams, D. A.
A1 - Zitzer, B.
A1 - McCollough, M. L.
T1 - Veritas observatons of the microquasar cygnus X-3
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We report results from TeV gamma-ray observations of the microquasar Cygnus X-3. The observations were made with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) over a time period from 2007 June 11 to 2011 November 28. VERITAS is most sensitive to gamma rays at energies between 85 GeV and 30 TeV. The effective exposure time amounts to a total of about 44 hr, with the observations covering six distinct radio/X-ray states of the object. No significant TeV gamma-ray emission was detected in any of the states, nor with all observations combined. The lack of a positive signal, especially in the states where GeV gamma rays were detected, places constraints on TeV gamma-ray production in Cygnus X-3. We discuss the implications of the results.
KW - acceleration of particles
KW - binaries: close
KW - gamma rays: stars
KW - X-rays: individual (Cygnus X-3)
Y1 - 2013
U6 - http://dx.doi.org/10.1088/0004-637X/779/2/150
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 779
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Archambault, S.
A1 - Aune, T.
A1 - Behera, B.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Biteau, J.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, Wei
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, Daniel
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Ackermann, Margit
A1 - Ajello, M.
A1 - Albert, A.
A1 - Baldini, L.
A1 - Bastieri, D.
A1 - Bellazzini, R.
A1 - Bissaldi, E.
A1 - Bregeon, J.
A1 - Buehler, R.
A1 - Buson, S.
A1 - Caliandro, G. A.
A1 - Cameron, R. A.
A1 - Caraveo, P. A.
A1 - Cavazzuti, E.
A1 - Charles, E.
A1 - Chiang, J.
A1 - Ciprini, S.
A1 - Claus, R.
A1 - Cutini, S.
A1 - de Angelis, A.
A1 - de Palma, F.
A1 - Dermer, C. D.
A1 - Digel, S. W.
A1 - Di Venere, L.
A1 - Drell, P. S.
A1 - Favuzzi, C.
A1 - Franckowiak, A.
A1 - Fusco, P.
A1 - Gargano, F.
A1 - Gasparrini, D.
A1 - Giglietto, N.
A1 - Giordano, F.
A1 - Giroletti, M.
A1 - Grenier, I. A.
A1 - Guiriec, S.
A1 - Jogler, T.
A1 - Kuss, M.
A1 - Larsson, S.
A1 - Latronico, L.
A1 - Longo, F.
A1 - Loparco, F.
A1 - Lubrano, P.
A1 - Madejski, G. M.
A1 - Mayer, M.
A1 - Mazziotta, M. N.
A1 - Michelson, P. F.
A1 - Mizuno, T.
A1 - Monzani, M. E.
A1 - Morselli, Aldo
A1 - Murgia, S.
A1 - Nuss, E.
A1 - Ohsugi, T.
A1 - Ormes, J. F.
A1 - Paneque, D.
A1 - Perkins, J. S.
A1 - Piron, F.
A1 - Pivato, G.
A1 - Raino, S.
A1 - Razzano, M.
A1 - Reimer, A.
A1 - Reimer, Olaf
A1 - Ritz, S.
A1 - Schaal, M.
A1 - Sgro, C.
A1 - Siskind, E. J.
A1 - Spinelli, P.
A1 - Takahashi, H.
A1 - Tibaldo, L.
A1 - Tinivella, M.
A1 - Troja, E.
A1 - Vianello, G.
A1 - Werner, M.
A1 - Wood, M.
T1 - Deep broadband observations of the distant gamma-ray blazar PKS 1424+240
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2 - 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.
KW - BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation
KW - gamma rays: galaxies
Y1 - 2014
U6 - http://dx.doi.org/10.1088/2041-8205/785/1/L16
SN - 2041-8205 (print)
SN - 2041-8213 (online)
VL - 785
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Archambault, S.
A1 - Arlen, T.
A1 - Aune, T.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Boettcher, M.
A1 - Bouvier, A.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickherber, R.
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gall, D.
A1 - Garson, A. III.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Grube, J.
A1 - Gusbar, C.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Lamerato, A.
A1 - Lang, M. J.
A1 - Li, K.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Orr, M.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Roustazadeh, P.
A1 - Saxon, D. B.
A1 - Sembroski, G. H.
A1 - Senturk, G. D.
A1 - Skole, C.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tesic, G.
A1 - Theiling, M.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - Test of models of the cosmic infrared background with multiwavelength observations of the blazar 1ES 1218+30.4 IN 2009
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - 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.
KW - BL Lacertae objects: general
KW - BL Lacertae objects: individual (1ES1218+30.4)
KW - cosmic background radiation
KW - diffuse radiation
KW - galaxies: jets
KW - gamma rays: galaxies
Y1 - 2014
U6 - http://dx.doi.org/10.1088/0004-637X/788/2/158
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 788
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Aune, T.
A1 - Behera, B.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Bouvier, A.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dumm, J.
A1 - Dwarkadas, V. V.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Gotthelf, E. V.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kargaltsev, O.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Pandel, D.
A1 - Park, N.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Roberts, M.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - Spatially resolving the very high energy emission from MRGO J2019+37 wih veritas
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended (similar to 2 degrees) unidentified Milagro source is located toward the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint, point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) with no evidence of a supernova remnant shell at the present time. Its spectrum is well fit in the 0.65-10 TeV energy range by a power-law model with photon index 2.3 +/- 0.4. VER J2019+378 is a bright extended (similar to 1 degrees) source that likely accounts for the bulk of the Milagro emission and is notably coincident with PSR J2021+3651 and the star formation region Sh 2-104. Its spectrum in the range 1-30 TeV is well fit with a power-law model of photon index 1.75 +/- 0.3, among the hardest values measured in the VHE band, comparable to that observed near Vela-X. We explore the unusual spectrum and morphology in the radio and X-ray bands to constrain possible emission mechanisms for this source.
KW - gamma rays : stars
KW - pulsars : individual (PSR J2021+3651)
KW - supernovae : individual (CTB 87)
Y1 - 2014
U6 - http://dx.doi.org/10.1088/0004-637X/788/1/78
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 788
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Aune, T.
A1 - Behera, B.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dumm, J.
A1 - Dwarkadas, V. V.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gall, D.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - McCann, A. J.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Pandel, D.
A1 - Park, N.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Ratliff, G.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Rousselle, J.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Sheidaei, F.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tsurusaki, K.
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Ward, J. E.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, Alina
T1 - Investigating the TeV morpholoy of MGRO J1908+06 with veritas
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with the VERITAS very high energy gamma-ray observatory. Previously, the TeV emission has been attributed to the pulsar wind nebula (PWN) of the Fermi-LAT pulsar PSR J1907+0602. We detect MGRO J1908+06 at a significance level of 14 standard deviations (14 sigma) and measure a photon index of 2.20 +/- 0.10(stat) +/- 0.20(sys). The TeV emission is extended, covering the region near PSR J1907+0602 and also extending toward SNR G40.5-0.5. When fitted with a two-dimensional Gaussian, the intrinsic extension has a standard deviation of sigma(src) = 0 degrees.44 +/- 0 degrees.02. In contrast to other TeV PWNe of similar age in which the TeV spectrum softens with distance from the pulsar, the TeV spectrum measured near the pulsar location is consistent with that measured at a position near the rim of G40.5-0.5, 0 degrees.33 away.
KW - gamma rays: general
KW - gamma-ray burst: individual (MGRO J1908+06, VER J1907+062)
KW - pulsars: individual (PSR J1907+0602)
KW - ISM: supernova remnants
Y1 - 2014
U6 - http://dx.doi.org/10.1088/0004-637X/787/2/166
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 787
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Aune, T.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Bouvier, A.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Lyutikov, M.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, M.
A1 - Popkow, A.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Sheidaei, F.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Theiling, M.
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zajczyk, A.
A1 - Zitzer, B.
T1 - A search for enhanced very high energy GAMMA-RAY emission from the 2013 march crab nebula flare
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2 - In 2013 March, a flaring episode from the Crab Nebula lasting similar to 2 weeks was detected by Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) provides simultaneous observations throughout this period. During the flare, Fermi-LAT detected a 20 fold increase in flux above the average synchrotron flux >100 MeV seen from the Crab Nebula. Simultaneous measurements with VERITAS are consistent with the non-variable long-term average Crab Nebula flux at TeV energies. Assuming a linear correlation between the very high energy flux change >1 TeV and the flux change seen in the Fermi-LAT band >100 MeV during the period of simultaneous observations, the linear correlation factor can be constrained to be at most 8.6 x 10(-3) with 95% confidence.
KW - gamma rays: general
KW - ISM: individual objects (Crab Nebula)
Y1 - 2014
U6 - http://dx.doi.org/10.1088/2041-8205/781/1/L11
SN - 2041-8205 (print)
SN - 2041-8213 (online)
VL - 781
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Aune, T.
A1 - Behera, B.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, X.
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Duke, C.
A1 - Dumm, J.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Kaaret, P.
A1 - Kargaltsev, Oleg
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - McCann, A.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Pandel, D.
A1 - Perkins, J. S.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Skole, C.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Theiling, M.
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - Observations of the unidentified gamm-ray source TeV J2032+4130 BY Veritas
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
KW - gamma rays: general
KW - pulsars: individual (PSR J2032+4127)
Y1 - 2014
U6 - http://dx.doi.org/10.1088/0004-637X/783/1/16
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 783
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Aune, T.
A1 - Barnacka, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Biteau, J.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connaughton, V.
A1 - Cui, W.
A1 - Dickinson, H. J.
A1 - Eisch, J. D.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Krennrich, F.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weiner, O. M.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Zitzer, B.
A1 - McEnery, J. E.
A1 - Perkins, J. S.
A1 - Veres, P.
A1 - Zhu, S.
T1 - Constraints on very high energy emission from GRB 130427A
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2 - Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for similar to 70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB130427A similar to 71 ks (similar to 20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst.
KW - gamma-ray burst: individual (GRB 130427A)
Y1 - 2014
U6 - http://dx.doi.org/10.1088/2041-8205/795/1/L3
SN - 2041-8205 (print)
SN - 2041-8213 (online)
VL - 795
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Archer, A.
A1 - Barnacka, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Biteau, J.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, W.
A1 - Chen, Xiaoming
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickinson, H. J.
A1 - Dumm, J.
A1 - Eisch, J. D.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Hanna, D.
A1 - Holder, J.
A1 - Hughes, G.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Perkins, J. S.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Rajotte, J.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Wilhelm, A.
A1 - Williams, D. A.
A1 - Zajczyk, A.
A1 - Zitzer, B.
T1 - Very-high energy observations of the galactic center region by veritas IN 2010-2012
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - 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.
KW - astroparticle physics
KW - black hole physics
KW - Galaxy: center
KW - gamma rays: galaxies
KW - methods: data analysis
KW - radiation mechanisms: non-thermal
Y1 - 2014
U6 - http://dx.doi.org/10.1088/0004-637X/790/2/149
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 790
IS - 2
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Acharya, B. S.
A1 - Aramo, C.
A1 - Babic, A.
A1 - Barrio, J. A.
A1 - Baushev, Anton
A1 - Tjus, J. Becker
A1 - Berge, D.
A1 - Bohacova, M.
A1 - Bonardi, A.
A1 - Brown, A.
A1 - Bugaev, V.
A1 - Bulik, T.
A1 - Burton, M.
A1 - Busetto, G.
A1 - Caraveo, P.
A1 - Carosi, R.
A1 - Carr, J.
A1 - Chadwick, P.
A1 - Chudoba, J.
A1 - Conforti, V.
A1 - Connaughton, V.
A1 - Contreras, J. L.
A1 - Cotter, G.
A1 - Dazzi, F.
A1 - De Franco, A.
A1 - de la Calle, I.
A1 - Lopez, R. de los Reyes
A1 - De Lotto, B.
A1 - De Palma, F.
A1 - Di Girolamo, T.
A1 - Di Giulio, C.
A1 - Di Pierro, F.
A1 - Dournaux, J. -L.
A1 - Dwarkadas, V.
A1 - Ebr, J.
A1 - Egberts, K.
A1 - Fesquet, M.
A1 - Fleischhack, H.
A1 - Font, L.
A1 - Fontaine, G.
A1 - Foerster, A.
A1 - Füßling, Matthias
A1 - Garcia, B.
A1 - Lopez, R. Garcia
A1 - Garczarczyk, M.
A1 - Gargano, F.
A1 - Garrido, D.
A1 - Gaug, M.
A1 - Giglietto, N.
A1 - Giordano, F.
A1 - Giuliani, A.
A1 - Godinovic, N.
A1 - Gonzalez, M. M.
A1 - Grabarczyk, T.
A1 - Hassan, T.
A1 - Hoerandel, J.
A1 - Hrabovsky, M.
A1 - Hrupec, D.
A1 - Humensky, T. B.
A1 - Huovelin, J.
A1 - Jamrozy, M.
A1 - Janecek, P.
A1 - Kaaret, P. E.
A1 - Katz, U.
A1 - Kaufmann, S.
A1 - Khelifi, B.
A1 - Kluzniak, W.
A1 - Kocot, J.
A1 - Komin, N.
A1 - Kubo, H.
A1 - Kushida, J.
A1 - Lamanna, G.
A1 - Lee, W. H.
A1 - Lenain, J. -P.
A1 - Lohse, T.
A1 - Lombardi, S.
A1 - Lopez-Coto, R.
A1 - Lopez-Oramas, A.
A1 - Lucarelli, F.
A1 - Maccarone, M. C.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - Malaguti, G.
A1 - Mandat, D.
A1 - Mazziotta, M. N.
A1 - Meagher, K.
A1 - Mirabal, N.
A1 - Morselli, A.
A1 - Moulin, E.
A1 - Niemiec, J.
A1 - Nievas, M.
A1 - Nishijima, K.
A1 - Nosek, D.
A1 - Nunio, F.
A1 - Ohishi, M.
A1 - Ohm, S.
A1 - Ong, R. A.
A1 - Orito, R.
A1 - Otte, N.
A1 - Palatka, M.
A1 - Pareschi, G.
A1 - Pech, M.
A1 - Persic, M.
A1 - Pohl, Manuela
A1 - Prouza, M.
A1 - Quirrenbach, A.
A1 - Raino, S.
A1 - Fernandez, G. Rodriguez
A1 - Romano, P.
A1 - Rovero, A. C.
A1 - Rudak, B.
A1 - Schovanek, P.
A1 - Shayduk, M.
A1 - Siejkowski, H.
A1 - Sillanpaa, A.
A1 - Stefanik, S.
A1 - Stolarczyk, T.
A1 - Szanecki, M.
A1 - Szepieniec, T.
A1 - Tejedor, L. A.
A1 - Telezhinsky, Igor
A1 - Teshima, M.
A1 - Tibaldo, L.
A1 - Tibolla, O.
A1 - Tovmassian, G.
A1 - Travnicek, P.
A1 - Trzeciak, M.
A1 - Vallania, P.
A1 - van Eldik, C.
A1 - Vercellone, S.
A1 - Vigorito, C.
A1 - Wagner, S. J.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Wierzcholska, A.
A1 - Wilhelm, Alina
A1 - Wojcik, P.
A1 - Yoshikoshi, T.
T1 - The Cherenkov Telescope Array potential for the study of young supernova remnants
JF - Astroparticle physics
N2 - Supernova remnants (SNRs) are among the most important targets for gamma-ray observatories. Being prominent non-thermal sources, they are very likely responsible for the acceleration of the bulk of Galactic cosmic rays (CRS). To firmly establish the SNR paradigm for the origin of cosmic rays, it should be confirmed that protons are indeed accelerated in, and released from, SNRs with the appropriate flux and spectrum. This can be done by detailed theoretical models which account for microphysics of acceleration and various radiation processes of hadrons and leptons. The current generation of Cherenkov telescopes has insufficient sensitivity to constrain theoretical models. A new facility, the Cherenkov Telescope Array (CTA), will have superior capabilities and may finally resolve this long standing issue of high-energy astrophysics. We want to assess the capabilities of CTA to reveal the physics of various types of SNRs in the initial 2000 years of their evolution. During this time, the efficiency to accelerate cosmic rays is highest. We perform time-dependent simulations of the hydrodynamics, the magnetic fields, the cosmic-ray acceleration, and the non-thermal emission for type Ia, Ic and IIP SNRs. We calculate the CTA response to the y-ray emission from these SNRs for various ages and distances, and we perform a realistic analysis of the simulated data. We derive distance limits for the detectability and resolvability of these SNR types at several ages. We test the ability of CTA to reconstruct their morphological and spectral parameters as a function of their distance. Finally, we estimate how well CTA data will constrain the theoretical models. (C) 2014 Elsevier B.V. All rights reserved.
KW - Acceleration of particles
KW - Gamma rays: General
KW - ISM: Supernova remnants
KW - Radiation mechanisms: Non-termal
Y1 - 2015
U6 - http://dx.doi.org/10.1016/j.astropartphys.2014.08.005
SN - 0927-6505 (print)
SN - 1873-2852 (online)
VL - 62
SP - 152
EP - 164
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Orienti, M.
A1 - Finke, J.
A1 - Raiteri, C. M.
A1 - Hovatta, T.
A1 - Larsson, J.
A1 - Max-Moerbeck, W.
A1 - Perkins, J.
A1 - Readhead, A. C. S.
A1 - Richards, J. L.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Bugaev, V.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Dickinson, H. J.
A1 - Eisch, J. D.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Gerard, L.
A1 - Gillanders, G. H.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Holder, J.
A1 - Humensky, T. B.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Khassen, Y.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Maier, G.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Rousselle, J.
A1 - Santander, M.
A1 - Sembroski, G. H.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vassiliev, V. V.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zitzer, B.
T1 - The most powerful flaring activity from the NLSyl PMN J0948+0022
JF - Monthly notices of the Royal Astronomical Society
N2 - We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma-rays, PMN J0948+0022 (z = 0.5846). A y -ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 31) x 10 8 ph cm(-2) S-1 on 2013 January 1, corresponding to an apparent isotropic luminosity of similar to 1.5 x 1048 erg s(-1). The y -ray flaring period triggered Swift and Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations in addition to radio and optical monitoring by Owens Valley Radio Observatory, Monitoring Of Jets in Active galactic nuclei with VLBA Experiments, and Catalina Real-time Transient Survey. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the y -ray flare, reaching a record flux for this source from optical to y gamma-rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6-17 resulted in an upper limit of F>0.2 Trev < 4.0 x 10(-12) ph cm(-2) s(-1). We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.
KW - galaxies: active-galaxies: individual: PMN J0948+0022
KW - galaxies: nuclei
KW - galaxies: Seyfert
KW - gamma-rays: general
Y1 - 2015
U6 - http://dx.doi.org/10.1093/mnras/stu2251
SN - 0035-8711 (print)
SN - 1365-2966 (online)
VL - 446
IS - 3
SP - 2456
EP - 2467
PB - Oxford Univ. Press
CY - Oxford
ER -
TY - JOUR
A1 - Aliu, E.
A1 - Archambault, S.
A1 - Archer, A.
A1 - Aune, T.
A1 - Barnacka, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Byrum, K.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickinson, H. J.
A1 - Dumm, J.
A1 - Eisch, J. D.
A1 - Errando, M.
A1 - Falcone, A.
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Kansson, N. H. A.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Kieda, D.
A1 - Krennrich, F.
A1 - Kumar, S.
A1 - Lang, M. J.
A1 - Lyutikov, M.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Park, N.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Quinn, J.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Santander, M.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weinstein, A.
A1 - Williams, D. A.
A1 - Zajczyk, A.
A1 - Zitzer, B.
T1 - A search for pulsations from geminga above 100 GeV with veritas
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We present the results of 71.6 hr of observations of the Geminga pulsar (PSR J0633+1746) with the VERITAS very-high-energy gamma-ray telescope array. Data taken with VERITAS between 2007 November and 2013 February were phase-folded using a Geminga pulsar timing solution derived from data recorded by the XMM-Newton and Fermi-LAT space telescopes. No significant pulsed emission above 100 GeV is observed, and we report upper limits at the 95% confidence level on the integral flux above 135 GeV (spectral analysis threshold) of 4.0x10(-13) s(-1) cm(-2) and 1.7 x 10(-13) s(-1) cm(-2) for the two principal peaks in the emission profile. These upper limits, placed in context with phase-resolved spectral energy distributions determined from 5 yr of data from the Fermi-Large Area Telescope (LAT), constrain possible hardening of the Geminga pulsar emission spectra above similar to 50 GeV.
KW - gamma rays: stars
KW - pulsars: general
KW - pulsars: individual (PSR J0633+1746, Geminga)
Y1 - 2015
U6 - http://dx.doi.org/10.1088/0004-637X/800/1/61
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 800
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Furniss, A.
A1 - Noda, K.
A1 - Boggs, S.
A1 - Chiang, J.
A1 - Christensen, F.
A1 - Craig, W.
A1 - Giommi, P.
A1 - Hailey, C.
A1 - Harisson, F.
A1 - Madejski, G.
A1 - Nalewajko, K.
A1 - Perri, M.
A1 - Stern, D.
A1 - Urry, M.
A1 - Verrecchia, F.
A1 - Zhang, W.
A1 - Ahnen, M. L.
A1 - Ansoldi, S.
A1 - Antonelli, L. A.
A1 - Antoranz, P.
A1 - Babic, A.
A1 - Banerjee, B.
A1 - Bangale, P.
A1 - de Almeida, U. Barres
A1 - Barrio, J. A.
A1 - Becerra Gonzalez, J.
A1 - Bednarek, W.
A1 - Bernardini, E.
A1 - Biasuzzi, B.
A1 - Biland, A.
A1 - Blanch, O.
A1 - Bonnefoy, S.
A1 - Bonnoli, G.
A1 - Borracci, F.
A1 - Bretz, T.
A1 - Carmona, E.
A1 - Carosi, A.
A1 - Chatterjee, A.
A1 - Clavero, R.
A1 - Colin, P.
A1 - Colombo, E.
A1 - Contreras, J. L.
A1 - Cortina, J.
A1 - Covino, S.
A1 - Da Vela, P.
A1 - Dazzi, F.
A1 - De Angelis, A.
A1 - De Caneva, G.
A1 - De Lotto, B.
A1 - de Ona Wilhelmi, E.
A1 - Delgado Mendez, C.
A1 - Di Pierro, F.
A1 - Prester, Dijana Dominis
A1 - Dorner, D.
A1 - Doro, M.
A1 - Einecke, S.
A1 - Eisenacher Glawion, D.
A1 - Elsaesser, D.
A1 - Fernandez-Barral, A.
A1 - Fidalgo, D.
A1 - Fonseca, M. V.
A1 - Font, L.
A1 - Frantzen, K.
A1 - Fruck, C.
A1 - Galindo, D.
A1 - Garcia Lopez, R. J.
A1 - Garczarczyk, M.
A1 - Garrido Terrats, D.
A1 - Gaug, M.
A1 - Giammaria, P.
A1 - Godinovic, N.
A1 - Gonzalez Munoz, A.
A1 - Guberman, D.
A1 - Hanabata, Y.
A1 - Hayashida, M.
A1 - Herrera, J.
A1 - Hose, J.
A1 - Hrupec, D.
A1 - Hughes, G.
A1 - Idec, W.
A1 - Kellermann, H.
A1 - Kodani, K.
A1 - Konno, Y.
A1 - Kubo, H.
A1 - Kushida, J.
A1 - La Barbera, A.
A1 - Lelas, D.
A1 - Lewandowska, N.
A1 - Lindfors, E.
A1 - Lombardi, S.
A1 - Longo, F.
A1 - Lopez, M.
A1 - Lopez-Coto, R.
A1 - Lopez-Oramas, A.
A1 - Lorenz, E.
A1 - Majumdar, P.
A1 - Makariev, M.
A1 - Mallot, K.
A1 - Maneva, G.
A1 - Manganaro, M.
A1 - Mannheim, K.
A1 - Maraschi, L.
A1 - Marcote, B.
A1 - Mariotti, M.
A1 - Martinez, M.
A1 - Mazin, D.
A1 - Menzel, U.
A1 - Miranda, J. M.
A1 - Mirzoyan, R.
A1 - Moralejo, A.
A1 - Nakajima, D.
A1 - Neustroev, V.
A1 - Niedzwiecki, A.
A1 - Nievas Rosillo, M.
A1 - Nilsson, K.
A1 - Nishijima, K.
A1 - Orito, R.
A1 - Overkemping, A.
A1 - Paiano, S.
A1 - Palacio, J.
A1 - Palatiello, M.
A1 - Paneque, D.
A1 - Paoletti, R.
A1 - Paredes, J. M.
A1 - Paredes-Fortuny, X.
A1 - Persic, M.
A1 - Poutanen, J.
A1 - Moroni, P. G. Prada
A1 - Prandini, E.
A1 - Puljak, I.
A1 - Reinthal, R.
A1 - Rhode, W.
A1 - Ribo, M.
A1 - Rico, J.
A1 - Garcia, J. Rodriguez
A1 - Saito, T.
A1 - Saito, K.
A1 - Satalecka, K.
A1 - Scapin, V.
A1 - Schultz, C.
A1 - Schweizer, T.
A1 - Shore, S. N.
A1 - Sillanpaa, A.
A1 - Sitarek, J.
A1 - Snidaric, I.
A1 - Sobczynska, D.
A1 - Stamerra, A.
A1 - Steinbring, T.
A1 - Strzys, M.
A1 - Takalo, L.
A1 - Takami, H.
A1 - Tavecchio, F.
A1 - Temnikov, P.
A1 - Terzic, T.
A1 - Tescaro, D.
A1 - Teshima, M.
A1 - Thaele, J.
A1 - Torres, D. F.
A1 - Toyama, T.
A1 - Treves, A.
A1 - Verguilov, V.
A1 - Vovk, I.
A1 - Will, M.
A1 - Zanin, R.
A1 - Archer, A.
A1 - Benbow, W.
A1 - Bird, R.
A1 - Biteau, J.
A1 - Bugaev, V.
A1 - Cardenzana, J. V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Connolly, M. P.
A1 - Cui, W.
A1 - Dickinson, H. J.
A1 - Dumm, J.
A1 - Eisch, J. D.
A1 - Falcone, A.
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fleischhack, H.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Gerard, L.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Holder, J.
A1 - Humensky, T. B.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Kieda, D.
A1 - Krause, M.
A1 - Krennrich, F.
A1 - Lang, M. J.
A1 - Lin, T. T. Y.
A1 - Maier, G.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Park, N.
A1 - Petry, D.
A1 - Pohl, Martin
A1 - Popkow, A.
A1 - Ragan, K.
A1 - Ratliff, G.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Santander, M.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Vassiliev, V. V.
A1 - Wakely, S. P.
A1 - Weiner, O. M.
A1 - Weinstein, A.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Zitzer, B.
A1 - Vince, O.
A1 - Fuhrmann, L.
A1 - Angelakis, E.
A1 - Karamanavis, V.
A1 - Myserlis, I.
A1 - Krichbaum, T. P.
A1 - Zensus, J. A.
A1 - Ungerechts, H.
A1 - Sievers, A.
A1 - Bachev, R.
A1 - Boettcher, M.
A1 - Chen, W. P.
A1 - Damljanovic, G.
A1 - Eswaraiah, C.
A1 - Guver, T.
A1 - Hovatta, T.
A1 - Hughes, Z.
A1 - Ibryamov, S. I.
A1 - Joner, M. D.
A1 - Jordan, B.
A1 - Jorstad, S. G.
A1 - Joshi, M.
A1 - Kataoka, J.
A1 - Kurtanidze, O. M.
A1 - Kurtanidze, S. O.
A1 - Lahteenmaki, A.
A1 - Latev, G.
A1 - Lin, H. C.
A1 - Larionov, V. M.
A1 - Mokrushina, A. A.
A1 - Morozova, D. A.
A1 - Nikolashvili, M. G.
A1 - Raiteri, C. M.
A1 - Ramakrishnan, V.
A1 - Readhead, A. C. R.
A1 - Sadun, A. C.
A1 - Sigua, L. A.
A1 - Semkov, E. H.
A1 - Strigachev, A.
A1 - Tammi, J.
A1 - Tornikoski, M.
A1 - Troitskaya, Y. V.
A1 - Troitsky, I. S.
A1 - Villata, M.
T1 - First NuSTAR observations of MRK 501 within a radio to TeV multi-instrument campaign
JF - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2 - We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 2013 April 1 and August 10, including the first detailed characterization of the synchrotron peak with Swift and NuSTAR. During the campaign, the nearby BL Lac object was observed in both a quiescent and an elevated state. The broadband campaign includes observations with NuSTAR, MAGIC, VERITAS, the Fermi Large Area Telescope, Swift X-ray Telescope and UV Optical Telescope, various ground-based optical instruments, including the GASP-WEBT program, as well as radio observations by OVRO, Metsahovi, and the F-Gamma consortium. Some of the MAGIC observations were affected by a sand layer from the Saharan desert, and had to be corrected using event-by-event corrections derived with a Light Detection and Ranging (LIDAR) facility. This is the first time that LIDAR information is used to produce a physics result with Cherenkov Telescope data taken during adverse atmospheric conditions, and hence sets a precedent for the current and future ground-based gamma-ray instruments. The NuSTAR instrument provides unprecedented sensitivity in hard X-rays, showing the source to display a spectral energy distribution (SED) between 3 and 79 keV consistent with a log-parabolic spectrum and hard X-ray variability on hour timescales. None (of the four extended NuSTAR observations) show evidence of the onset of inverse-Compton emission at hard X-ray energies. We apply a single-zone equilibrium synchrotron self-Compton (SSC) model to five simultaneous broadband SEDs. We find that the SSC model can reproduce the observed broadband states through a decrease in the magnetic field strength coinciding with an increase in the luminosity and hardness of the relativistic leptons responsible for the high-energy emission.
KW - BL Lacertae objects: general
KW - galaxies: individual (Markarian 501)
KW - X-rays: galaxies
Y1 - 2015
U6 - http://dx.doi.org/10.1088/0004-637X/812/1/65
SN - 0004-637X (print)
SN - 1538-4357 (online)
VL - 812
IS - 1
PB - IOP Publ. Ltd.
CY - Bristol
ER -
TY - JOUR
A1 - Aleksic, J.
A1 - Ansoldi, S.
A1 - Antonelli, L. A.
A1 - Antoranz, P.
A1 - Babic, A.
A1 - Bangale, P.
A1 - de Almeida, U. Barres
A1 - Barrio, J. A.
A1 - Gonzalez, J. Becerra
A1 - Bednarek, W.
A1 - Bernardini, E.
A1 - Biasuzzi, B.
A1 - Biland, A.
A1 - Blanch, O.
A1 - Boller, A.
A1 - Bonnefoy, S.
A1 - Bonnoli, G.
A1 - Borracci, F.
A1 - Bretz, T.
A1 - Carmona, E.
A1 - Carosi, A.
A1 - Colin, P.
A1 - Colombo, E.
A1 - Contreras, J. L.
A1 - Cortina, J.
A1 - Covino, S.
A1 - Da Vela, P.
A1 - Dazzi, F.
A1 - De Angelis, A.
A1 - De Caneva, G.
A1 - De Lotto, B.
A1 - Wilhelmi, E. de Ona
A1 - Mendez, C. Delgado
A1 - Prester, Dijana Dominis
A1 - Dorner, D.
A1 - Doro, M.
A1 - Einecke, S.
A1 - Eisenacher, D.
A1 - Elsaesser, D.
A1 - Fonseca, M. V.
A1 - Font, L.
A1 - Frantzen, K.
A1 - Fruck, C.
A1 - Galindo, D.
A1 - Lopez, R. J. Garcia
A1 - Garczarczyk, M.
A1 - Terrats, D. Garrido
A1 - Gaug, M.
A1 - Godinovic, N.
A1 - Munoz, A. Gonzalez
A1 - Gozzini, S. R.
A1 - Hadasch, D.
A1 - Hanabata, Y.
A1 - Hayashida, M.
A1 - Herrera, J.
A1 - Hildebrand, D.
A1 - Hose, J.
A1 - Hrupec, D.
A1 - Hughes, G.
A1 - Idec, W.
A1 - Kadenius, V.
A1 - Kellermann, H.
A1 - Knoetig, M. L.
A1 - Kodani, K.
A1 - Konno, Y.
A1 - Krause, J.
A1 - Kubo, H.
A1 - Kushida, J.
A1 - La Barbera, A.
A1 - Lelas, D.
A1 - Lewandowska, N.
A1 - Lindfors, E.
A1 - Lombardi, S.
A1 - Lopez, M.
A1 - Lopez-Coto, R.
A1 - Lopez-Oramas, A.
A1 - Lorenz, E.
A1 - Lozano, I.
A1 - Makariev, M.
A1 - Mallot, K.
A1 - Maneva, G.
A1 - Mankuzhiyil, N.
A1 - Mannheim, K.
A1 - Maraschi, L.
A1 - Marcote, B.
A1 - Mariotti, M.
A1 - Martinez, M.
A1 - Mazin, D.
A1 - Menzel, U.
A1 - Miranda, J. M.
A1 - Mirzoyan, R.
A1 - Moralejo, A.
A1 - Munar-Adrover, P.
A1 - Nakajima, D.
A1 - Niedzwiecki, A.
A1 - Nilsson, K.
A1 - Nishijima, K.
A1 - Noda, K.
A1 - Orito, R.
A1 - Overkemping, A.
A1 - Paiano, S.
A1 - Palatiello, M.
A1 - Paneque, D.
A1 - Paoletti, R.
A1 - Paredes, J. M.
A1 - Paredes-Fortuny, X.
A1 - Persic, M.
A1 - Moroni, P. G. Prada
A1 - Prandini, E.
A1 - Puljak, I.
A1 - Reinthal, R.
A1 - Rhode, W.
A1 - Ribo, M.
A1 - Rico, J.
A1 - Garcia, J. Rodriguez
A1 - Rugamer, S.
A1 - Saito, T.
A1 - Saito, K.
A1 - Satalecka, K.
A1 - Scalzotto, V.
A1 - Scapin, V.
A1 - Schultz, C.
A1 - Schweizer, T.
A1 - Sun, S.
A1 - Shore, S. N.
A1 - Sillanpaa, A.
A1 - Sitarek, J.
A1 - Snidaric, I.
A1 - Sobczynska, D.
A1 - Spanier, F.
A1 - Stamatescu, V.
A1 - Stamerra, A.
A1 - Steinbring, T.
A1 - Steinke, B.
A1 - Storz, J.
A1 - Strzys, M.
A1 - Takalo, L.
A1 - Takami, H.
A1 - Tavecchio, F.
A1 - Temnikov, P.
A1 - Terzic, T.
A1 - Tescaro, D.
A1 - Teshima, M.
A1 - Thaele, J.
A1 - Tibolla, O.
A1 - Torres, D. F.
A1 - Toyama, T.
A1 - Treves, A.
A1 - Uellenbeck, M.
A1 - Vogler, P.
A1 - Zanin, R.
A1 - Archambault, S.
A1 - Archer, A.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Biteau, J.
A1 - Buckley, J. H.
A1 - Bugaev, V.
A1 - Cerruti, M.
A1 - Chen, Xiaoming
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Cui, W.
A1 - Eisch, J. D.
A1 - Falcone, A.
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortin, P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Gyuk, G.
A1 - Hakansson, Nils
A1 - Holder, J.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kar, P.
A1 - Kertzman, M.
A1 - Kieda, D.
A1 - Lang, M. J.
A1 - McArthur, S.
A1 - McCann, A.
A1 - Meagher, K.
A1 - Millis, J.
A1 - Moriarty, P.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Perkins, J. S.
A1 - Pichel, A.
A1 - Pohl, Manuela
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Pueschel, E.
A1 - Ragan, K.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Rovero, A. C.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Tucci, J. V.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Wakely, S. P.
A1 - Welsing, R.
A1 - Wilhelm, Alina
A1 - Williams, D. A.
A1 - Buson, S.
A1 - Finke, J.
A1 - Villata, M.
A1 - Raiteri, C.
A1 - Aller, H. D.
A1 - Aller, M. F.
A1 - Cesarini, A.
A1 - Chen, W. P.
A1 - Gurwell, M. A.
A1 - Jorstad, S. G.
A1 - Kimeridze, G. N.
A1 - Koptelova, E.
A1 - Kurtanidze, O. M.
A1 - Kurtanidze, S. O.
A1 - Lahteenmaki, A.
A1 - Larionov, V. M.
A1 - Larionova, E. G.
A1 - Lin, H. C.
A1 - McBreen, B.
A1 - Moody, J. W.
A1 - Morozova, D. A.
A1 - Marscher, A. P.
A1 - Max-Moerbeck, W.
A1 - Nikolashvili, M. G.
A1 - Perri, M.
A1 - Readhead, A. C. S.
A1 - Richards, J. L.
A1 - Ros, J. A.
A1 - Sadun, A. C.
A1 - Sakamoto, T.
A1 - Sigua, L. A.
A1 - Smith, P. S.
A1 - Tornikoski, M.
A1 - Troitsky, I. S.
A1 - Wehrle, A. E.
A1 - Jordan, B.
T1 - Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010
JF - Astronomy and astrophysics : an international weekly journal
N2 - 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.
KW - radiation mechanisms: non-thermal
KW - galaxies: active
KW - BL Lacertae objects: individual: Mrk 421
KW - gamma rays: galaxies
Y1 - 2015
U6 - http://dx.doi.org/10.1051/0004-6361/201424811
SN - 0004-6361 (print)
SN - 1432-0746 (online)
VL - 578
PB - EDP Sciences
CY - Les Ulis
ER -
TY - JOUR
A1 - Aleksic, J.
A1 - Ansoldi, S.
A1 - Antonelli, L. A.
A1 - Antoranz, P.
A1 - Babic, A.
A1 - Bangale, P.
A1 - de Almeida, U. Barres
A1 - Barrio, J. A.
A1 - Becerra Gonzalez, J.
A1 - Bednarek, W.
A1 - Berger, K.
A1 - Bernardini, E.
A1 - Biland, A.
A1 - Blanch, O.
A1 - Bock, R. K.
A1 - Bonnefoy, S.
A1 - Bonnoli, G.
A1 - Borracci, F.
A1 - Bretz, T.
A1 - Carmona, E.
A1 - Carosi, A.
A1 - Fidalgo, D. Carreto
A1 - Colin, P.
A1 - Colombo, E.
A1 - Contreras, J. L.
A1 - Cortina, J.
A1 - Covino, S.
A1 - Da Vela, P.
A1 - Dazzi, F.
A1 - De Angelis, A.
A1 - De Caneva, G.
A1 - De Lotto, B.
A1 - Delgado Mendez, C.
A1 - Doert, M.
A1 - Dominguez, A.
A1 - Prester, Dijana Dominis
A1 - Dorner, D.
A1 - Doro, M.
A1 - Einecke, S.
A1 - Eisenacher, D.
A1 - Elsaesser, D.
A1 - Farina, E.
A1 - Ferenc, D.
A1 - Fonseca, M. V.
A1 - Font, L.
A1 - Frantzen, K.
A1 - Fruck, C.
A1 - Garcia Lopez, R. J.
A1 - Garczarczyk, M.
A1 - Garrido Terrats, D.
A1 - Gaug, M.
A1 - Giavitto, G.
A1 - Godinovic, N.
A1 - Gonzalez Munoz, A.
A1 - Gozzini, S. R.
A1 - Hadamek, A.
A1 - Hadasch, D.
A1 - Herrero, A.
A1 - Hildebrand, D.
A1 - Hose, J.
A1 - Hrupec, D.
A1 - Idec, W.
A1 - Kadenius, V.
A1 - Kellermann, H.
A1 - Knoetig, M. L.
A1 - Krause, J.
A1 - Kushida, J.
A1 - La Barbera, A.
A1 - Lelas, D.
A1 - Lewandowska, N.
A1 - Lindfors, E.
A1 - Lombardi, S.
A1 - Lopez, M.
A1 - Lopez-Coto, R.
A1 - Lopez-Oramas, A.
A1 - Lorenz, E.
A1 - Lozano, I.
A1 - Makariev, M.
A1 - Mallot, K.
A1 - Maneva, G.
A1 - Mankuzhiyil, N.
A1 - Mannheim, K.
A1 - Maraschi, L.
A1 - Marcote, B.
A1 - Mariotti, M.
A1 - Martinez, M.
A1 - Mazin, D.
A1 - Menzel, U.
A1 - Meucci, M.
A1 - Miranda, J. M.
A1 - Mirzoyan, R.
A1 - Moralejo, A.
A1 - Munar-Adrover, P.
A1 - Nakajima, D.
A1 - Niedzwiecki, A.
A1 - Nilsson, K.
A1 - Nowak, N.
A1 - Orito, R.
A1 - Overkemping, A.
A1 - Paiano, S.
A1 - Palatiello, M.
A1 - Paneque, D.
A1 - Paoletti, R.
A1 - Paredes, J. M.
A1 - Paredes-Fortuny, X.
A1 - Partini, S.
A1 - Persic, M.
A1 - Prada, F.
A1 - Moroni, P. G. Prada
A1 - Prandini, E.
A1 - Preziuso, S.
A1 - Puljak, I.
A1 - Reinthal, R.
A1 - Rhode, W.
A1 - Ribo, M.
A1 - Rico, J.
A1 - Garcia, J. Rodriguez
A1 - Ruegamer, S.
A1 - Saggion, A.
A1 - Saito, T.
A1 - Saito, K.
A1 - Salvati, M.
A1 - Satalecka, K.
A1 - Scalzotto, V.
A1 - Scapin, V.
A1 - Schultz, C.
A1 - Schweizer, T.
A1 - Shore, S. N.
A1 - Sillanpaa, A.
A1 - Sitarek, J.
A1 - Snidaric, I.
A1 - Sobczynska, D.
A1 - Spanier, F.
A1 - Stamatescu, V.
A1 - Stamerra, A.
A1 - Steinbring, T.
A1 - Storz, J.
A1 - Sun, S.
A1 - Suric, T.
A1 - Takalo, L.
A1 - Tavecchio, F.
A1 - Temnikov, P.
A1 - Terzic, T.
A1 - Tescaro, D.
A1 - Teshima, M.
A1 - Thaele, J.
A1 - Tibolla, O.
A1 - Torres, D. F.
A1 - Toyama, T.
A1 - Treves, A.
A1 - Uellenbeck, M.
A1 - Vogler, P.
A1 - Wagner, R. M.
A1 - Zandanel, F.
A1 - Zanin, R.
A1 - Behera, B.
A1 - Beilicke, M.
A1 - Benbow, W.
A1 - Berger, K.
A1 - Bird, R.
A1 - Bouvier, A.
A1 - Bugaev, V.
A1 - Cerruti, M.
A1 - Chen, Xuhui
A1 - Ciupik, L.
A1 - Collins-Hughes, E.
A1 - Cui, W.
A1 - Duke, C.
A1 - Dumm, J.
A1 - Falcone, A.
A1 - Federici, Simone
A1 - Feng, Q.
A1 - Finley, J. P.
A1 - Fortson, L.
A1 - Furniss, A.
A1 - Galante, N.
A1 - Gillanders, G. H.
A1 - Griffin, S.
A1 - Griffiths, S. T.
A1 - Grube, J.
A1 - Gyuk, G.
A1 - Hanna, D.
A1 - Holder, J.
A1 - Johnson, C. A.
A1 - Kaaret, P.
A1 - Kertzman, M.
A1 - Kieda, D.
A1 - Krawczynski, H.
A1 - Lang, M. J.
A1 - Madhavan, A. S.
A1 - Maier, G.
A1 - Majumdar, P.
A1 - Meagher, K.
A1 - Moriarty, P.
A1 - Mukherjee, R.
A1 - Nieto, D.
A1 - Ong, R. A.
A1 - Otte, A. N.
A1 - Pichel, A.
A1 - Pohl, Manula
A1 - Popkow, A.
A1 - Prokoph, H.
A1 - Quinn, J.
A1 - Rajotte, J.
A1 - Ratliff, G.
A1 - Reyes, L. C.
A1 - Reynolds, P. T.
A1 - Richards, G. T.
A1 - Roache, E.
A1 - Sembroski, G. H.
A1 - Shahinyan, K.
A1 - Sheidaei, F.
A1 - Smith, A. W.
A1 - Staszak, D.
A1 - Telezhinsky, Igor
A1 - Theiling, M.
A1 - Tyler, J.
A1 - Varlotta, A.
A1 - Vincent, S.
A1 - Wakely, S. P.
A1 - Weekes, T. C.
A1 - Welsing, R.
A1 - Williams, D. A.
A1 - Zajczyk, A.
A1 - Zitzer, B.
A1 - Villata, M.
A1 - Raiteri, C. M.
A1 - Ajello, M.
A1 - Perri, M.
A1 - Aller, H. D.
A1 - Aller, M. F.
A1 - Larionov, V. M.
A1 - Efimova, N. V.
A1 - Konstantinova, T. S.
A1 - Kopatskaya, E. N.
A1 - Chen, W. P.
A1 - Koptelova, E.
A1 - Hsiao, H. Y.
A1 - Kurtanidze, O. M.
A1 - Nikolashvili, M. G.
A1 - Kimeridze, G. N.
A1 - Jordan, B.
A1 - Leto, P.
A1 - Buemi, C. S.
A1 - Trigilio, C.
A1 - Umana, G.
A1 - Lahteenmaki, A.
A1 - Nieppola, E.
A1 - Tornikoski, M.
A1 - Sainio, J.
A1 - Kadenius, V.
A1 - Giroletti, M.
A1 - Cesarini, A.
A1 - Fuhrmann, L.
A1 - Kovalev, Yu. A.
A1 - Kovalev, Y. Y.
T1 - Multiwavelength observations of Mrk 501 in 2008
JF - Astronomy and astrophysics : an international weekly journal
N2 - Context. Blazars are variable sources on various timescales over a broad energy range spanning from radio to very high energy (>100 GeV, hereafter VHE). Mrk 501 is one of the brightest blazars at TeV energies and has been extensively studied since its first VHE detection in 1996. However, most of the gamma-ray studies performed on Mrk 501 during the past years relate to flaring activity, when the source detection and characterization with the available gamma-ray instrumentation was easier to perform.
Aims. Our goal is to characterize the source gamma-ray emission in detail, together with the radio-to-X-ray emission, during the non-flaring (low) activity, which is less often studied than the occasional flaring (high) activity.
Methods. We organized a multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This multi-instrument effort included the most sensitive VHE gamma-ray instruments in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other collaborations and instruments. This provided extensive energy and temporal coverage of Mrk 501 throughout the entire campaign.
Results. Mrk 501 was found to be in a low state of activity during the campaign, with a VHE flux in the range of 10%-20% of the Crab nebula flux. Nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy and a tentative correlation between the X-ray and VHE fluxes. The broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-Compton model, with the (slightly) higher state described by an increase in the electron number density.
Conclusions. The one-zone SSC model can adequately describe the broadband spectral energy distribution of the source during the two months covered by the MW campaign. This agrees with previous studies of the broadband emission of this source during flaring and non-flaring states. We report for the first time a tentative X-ray-to-VHE correlation during such a low VHE activity. Although marginally significant, this positive correlation between X-ray and VHE, which has been reported many times during flaring activity, suggests that the mechanisms that dominate the X-ray/VHE emission during non-flaring-activity are not substantially different from those that are responsible for the emission during flaring activity.
KW - astroparticle physics
KW - BL Lacertae objects: individual: Mrk 501
KW - gamma rays: general
Y1 - 2015
U6 - http://dx.doi.org/10.1051/0004-6361/201322906
SN - 0004-6361 (print)
SN - 1432-0746 (online)
VL - 573
PB - EDP Sciences
CY - Les Ulis
ER -
TY - JOUR
A1 - Pohl, Manuela
A1 - Wilhelm, Alina
A1 - Telezhinsky, Igor
T1 - Reacceleration of electrons in supernova remnants
JF - Astronomy and astrophysics : an international weekly journal
N2 - Context. radio spectra of many shell-type supernova remnants show deviations from those expected on theoretical grounds.
Aims. In this paper we determine the effect of stochastic reacceleration on the spectra of electrons in the GeV band and at lower energies, and we investigate whether reacceleration can explain the observed variation in radio spectral indices.
Methods. We explicitely calculated the momentum diffusion coefficient for 3 types of turbulence expected downstream of the forward shock: fast-mode waves, small-scale non-resonant modes, and large-scale modes arising from turbulent dynamo activity. After noting that low-energy particles are efficiently coupled to the quasi-thermal plasma, a simplified cosmic-ray transport equation can be formulated and is numerically solved.
Results. Only fast-mode waves can provide momentum diffusion fast enough to significantly modify the spectra of particles. Using a synchrotron emissivity that accurately reflects a highly turbulent magnetic field, we calculated the radio spectral index and find that soft spectra with index a alpha less than or similar to -0.6 can be maintained over more than 2 decades in radio frequency, even if the electrons experience reacceleration for only one acceleration time. A spectral hardening is possible but considerably more frequency-dependent. The spectral modification imposed by stochastic reacceleration downstream of the forward shock depends only weakly on the initial spectrum provided by, e.g., diffusive shock acceleration at the shock itself.
KW - acceleration of particles
KW - turbulence
KW - cosmic rays
KW - ISM: supernova remnants
Y1 - 2015
U6 - http://dx.doi.org/10.1051/0004-6361/201425027
SN - 0004-6361 (print)
SN - 1432-0746 (online)
VL - 574
PB - EDP Sciences
CY - Les Ulis
ER -
TY - JOUR
A1 - Federici, Simone
A1 - Pohl, Martin
A1 - Telezhinsky, Igor
A1 - Wilhelm, Alina
A1 - Dwarkadas, Vikram V.
T1 - Analysis of GeV-band gamma-ray emission from supernova remnant RX J1713.7-3946
JF - Astronomy and astrophysics : an international weekly journal
N2 - Context. RX J1713.7-3946 is the brightest shell-type supernova remnant (SNR) of the TeV gamma-ray sky. Earlier Fermi-LAT results on low energy gamma-ray emission suggested that, despite large uncertainties in the background determination, the spectrum is inconsistent with a hadronic origin.
Aims. We update the GeV-band spectra using improved estimates for the diffuse Galactic gamma-ray emission and more than double the volume of data. We further investigate the viability of hadronic emission models for RX J1713.7-3946.
Methods. We produced a high-resolution map of the diffuse Galactic gamma-ray background corrected for the HI self-absorption and used it in the analysis of more than five years worth of Fermi-LAT data. We used hydrodynamic scaling relations and a kinetic transport equation to calculate the acceleration and propagation of cosmic rays in SNR. We then determined spectra of hadronic gamma-ray emission from RX J1713.7-3946, separately for the SNR interior and the cosmic-ray precursor region of the forward shock, and computed flux variations that would allow us to test the model with observations.
Results. We find that RX J1713.7-3946 is now detected by Fermi-LAT with very high statistical significance, and the source morphology is best described by that seen in the TeV band. The measured spectrum of RX J1713.7-3946 is hard with index gamma = 1.53 +/- 0.07, and the integral flux above 500 MeV is F = (5 : 5 +/- 1 : 1) x 10(-9) photons cm(-2) s(-1). We demonstrate that scenarios based on hadronic emission from the cosmic-ray precursor region are acceptable for RX J1713.7-3946, and we predict a secular flux increase at a few hundred GeV at the level of around 15% over ten years, which may be detectable with the upcoming Cherenkov Telescope Array (CTA) observatory.
KW - astroparticle physics
KW - cosmic rays
KW - ISM: supernova remnants
KW - gamma rays: ISM
Y1 - 2015
U6 - http://dx.doi.org/10.1051/0004-6361/201424947
SN - 0004-6361 (print)
SN - 1432-0746 (online)
VL - 577
PB - EDP Sciences
CY - Les Ulis
ER -