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  • 151. Aliu, E.
    et al.
    Aune, T.
    Behera, B.
    Beilicke, M.
    Benbow, W.
    Berger, K.
    Bird, R.
    Buckley, J. H.
    Bugaev, V.
    Cardenzana, J. V.
    Cerruti, M.
    Chen, X.
    Ciupik, L.
    Connolly, M. P.
    Cui, W.
    Duke, C.
    Dumm, J.
    Errando, M.
    Falcone, A.
    Federici, S.
    Feng, Q.
    Finley, J. P.
    Fortin, P.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gillanders, G. H.
    Griffin, S.
    Griffiths, S. T.
    Grube, J.
    Gyuk, G.
    Hanna, D.
    Holder, J.
    Hughes, G.
    Humensky, T. B.
    Kaaret, P.
    Kargaltsev, O.
    Kertzman, M.
    Khassen, Y.
    Kieda, D.
    Krawczynski, H.
    Lang, M. J.
    Madhavan, A. S.
    Maier, G.
    Majumdar, P.
    McCann, A.
    Moriarty, P.
    Mukherjee, R.
    Nieto, D.
    O’Faoláin de Bhróithe, A.
    Ong, R. A.
    Otte, A. N.
    Pandel, D.
    Perkins, J. S.
    Pohl, M.
    Popkow, A.
    Prokoph, Heike
    DESY, Germany .
    Quinn, J.
    Ragan, K.
    Rajotte, J.
    Reyes, L. C.
    Reynolds, P. T.
    Richards, G. T.
    Roache, E.
    Sembroski, G. H.
    Skole, C.
    Staszak, D.
    Telezhinsky, I.
    Theiling, M.
    Tucci, J. V.
    Tyler, J.
    Varlotta, A.
    Vincent, S.
    Wakely, S. P.
    Weekes, T. C.
    Weinstein, A.
    Welsing, R.
    Williams, D. A.
    Zitzer, B.
    Observations of the Unidentified Gamma-Ray Source TeV J2032+4130 by VERITAS2014In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 783Article in journal (Refereed)
    Abstract [en]

    TeV J2032+4130 was the first unidentified source discovered at very high energies (VHEs; E > 100 GeV), with no obvious counterpart in any other wavelength. It is also the first extended source to be observed in VHE gamma rays. Following its discovery, intensive observational campaigns have been carried out in all wavelengths in order to understand the nature of the object, which have met with limited success. We report here on a deep observation of TeV J2032+4130   based on 48.2 hr of data taken from 2009 to 2012 by the Very Energetic Radiation Imaging Telescope Array System experiment. The source is detected at 8.7 standard deviations (σ) and is found to be extended and asymmetric with a width of 9.'5 ± 1.'2 along the major axis and 4.'0 ± 0.'5 along the minor axis. The spectrum is well described by a differential power law with an index of 2.10 ± 0.14stat ± 0.21sys and a normalization of (9.5 ± 1.6stat ± 2.2sys× 10–13 TeV–1 cm–2 s–1 at 1 TeV. We interpret these results in the context of multiwavelength scenarios which particularly favor the pulsar wind nebula interpretation.

  • 152. Aliu, E.
    et al.
    Aune, T.
    Beilicke, M.
    Benbow, W.
    Böttcher, M.
    Bouvier, A.
    Bradbury, S. M.
    Buckley, J. H.
    Bugaev, V.
    Cannon, A.
    Cesarini, A.
    Ciupik, L.
    Connolly, M. P.
    Cui, W.
    Decerprit, G.
    Dickherber, R.
    Duke, C.
    Errando, M.
    Falcone, A.
    Feng, Q.
    Finnegan, G.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gall, D.
    Gillanders, G. H.
    Godambe, S.
    Griffin, S.
    Grube, J.
    Gyuk, G.
    Hanna, D.
    Hivick, B.
    Holder, J.
    Huan, H.
    Hughes, G.
    Hui, C. M.
    Humensky, T. B.
    Kaaret, P.
    Karlsson, N.
    Kertzman, M.
    Kieda, D.
    Krawczynski, H.
    Krennrich, F.
    Maier, G.
    Majumdar, P.
    McArthur, S.
    McCann, A.
    Moriarty, P.
    Mukherjee, R.
    Nelson, T.
    Ong, R. A.
    Orr, M.
    Otte, A. N.
    Park, N.
    Perkins, J. S.
    Pichel, A.
    Pohl, M.
    Prokoph, Heike
    DESY, Germany.
    Quinn, J.
    Ragan, K.
    Reyes, L. C.
    Reynolds, P. T.
    Roache, E.
    Rose, H. J.
    Ruppel, J.
    Saxon, D. B.
    Sembroski, G. H.
    Skole, C.
    Smith, A. W.
    Staszak, D.
    Tesić, G.
    Theiling, M.
    Thibadeau, S.
    Tsurusaki, K.
    Tyler, J.
    Varlotta, A.
    Vassiliev, V. V.
    Wakely, S. P.
    Weekes, T. C.
    Weinstein, A.
    Williams, D. A.
    Zitzer, B.
    Collaboration, V E R I T A S
    Ciprini, S.
    Fumagalli, M.
    Kaplan, K.
    Paneque, D.
    Prochaska, J. X.
    Multiwavelength Observations of the Previously Unidentified Blazar RX J0648.7+15162011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 742, no 2, article id 127Article in journal (Refereed)
    Abstract [en]

    We report on the VERITAS discovery of very high energy (VHE) gamma-ray emission above 200 GeV from the high-frequency-peaked BL Lac (HBL) object RX J0648.7+1516 (GB J0648+1516), associated with 1FGL J0648.8+1516. The photon spectrum above 200 GeV is fitted by a power law dN/dE = F 0(E/E 0)–Γ with a photon index Γ of 4.4 ± 0.8stat ± 0.3syst and a flux normalization F 0 of (2.3 ± 0.5stat ± 1.2sys× 10–11 TeV–1 cm–2 s–1 with E 0 = 300 GeV. No VHE variability is detected during VERITAS observations of RX J0648.7+1516 between 2010 March 4 and April 15. Following the VHE discovery, the optical identification and spectroscopic redshift were obtained using the Shane 3 m Telescope at the Lick Observatory, showing the unidentified object to be a BL Lac type with a redshift of z = 0.179. Broadband multiwavelength observations contemporaneous with the VERITAS exposure period can be used to subclassify the blazar as an HBL object, including data from the MDM observatory, Swift-UVOT, and X-Ray Telescope, and continuous monitoring at photon energies above 1 GeV from the FermiLarge Area Telescope (LAT). We find that in the absence of undetected, high-energy rapid variability, the one-zone synchrotron self-Compton (SSC) model overproduces the high-energy gamma-ray emission measured by the Fermi-LAT over 2.3 years. The spectral energy distribution can be parameterized satisfactorily with an external-Compton or lepto-hadronic model, which have two and six additional free parameters, respectively, compared to the one-zone SSC model.

  • 153.
    Ambrosio, M
    et al.
    Università di Napoli, Italy ; INFN, Italy.
    Antolini, R
    Laboratori Nazionali del Gran Sasso dell’INFN, Italy.
    Auriemma, G
    Università di Roma “La Sapienza”, Italy ; INFN, Italy.
    Bakari, D
    Università di Bologna, Italy ; INFN, Italy ; University Mohamed I, Morocco.
    Baldini, A
    Università di Pisa, Italy ; INFN, Italy.
    Barbarino, G C
    Università di Napoli, Italy ; INFN, Italy.
    Barish, B C
    California Institute of Technology, USA.
    Battistoni, G
    INFN, Italy.
    Becherini, Yvonne
    Boston University, USA.
    Bellotti, R
    Università di Bari, Italy ; INFN. Italy.
    Bemporad, C
    Università di Pisa, Italy ; INFN, Italy.
    Bernardini, P
    Università di Lecce, Italy ; INFN, Italy.
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Chiarusi, T
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Kumar, A
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Manzoor, S
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Matteuzzi, D
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Final results of magnetic monopole searches with the MACRO experiment2002In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 25, no 4, p. 511-522Article in journal (Refereed)
    Abstract [en]

    We present the final results obtained by the MACRO experiment in the search for GUT magnetic monopoles in the penetrating cosmic radiation, for the range 4 x 10(-5) < 3 < 1. Several searches with all the MACRO sub-detectors (i.e. scintillation counters, limited streamer tubes and nuclear track detectors) were performed, both in stand alone and combined ways. No candidates were detected and a 90% Confidence Level (C.L.) upper limit to the local magnetic monopole flux was set at the level of 1.4 x 10(-16) cm(-2) s(-1) sr(-1). This result is the first experimental limit obtained in direct searches which is well below the Parker bound in the whole 3 range in which GUT magnetic monopoles are,expected.

  • 154. Ambrosio, M
    et al.
    Antolini, R
    Auriemma, G
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Manzoor, S
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Search for nucleon decays induced by GUT magnetic monopoles with the MACRO experiment2002In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 26, no 2, p. 163-172Article in journal (Refereed)
    Abstract [en]

    The interaction of a Grand Unification Magnetic Monopole with a nucleon can lead to a barion-number violating process in which the nucleon decays into a lepton and one or more mesons (catalysis of nucleon decay). In this paper we report an experimental study of the effects of a catalysis process in the MACRO detector. Using a dedicated analysis we obtain new magnetic monopole (MM) flux upper limits at the level of similar to 3 (.) 10(-16) cm(-2) s(-1) sr(-1) for 1.1(.) 10(-4) less than or equal to \beta\ less than or equal to 5 (.) 10(-3), based on the search for catalysis events in the MACRO data. We also analyze the dependence of the MM flux limit on the catalysis cross section.

  • 155. Ambrosio, M
    et al.
    Antolini, R
    Auriemma, G
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Search for cosmic ray sources using muons detected by the MACRO experiment2003In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 18, no 6, p. 615-627Article in journal (Refereed)
    Abstract [en]

    The MACRO underground detector at Gran Sasso Laboratory recorded 60 million secondary cosmic ray muons from February 1989 until December 2000. Different techniques were used to analyze this sample in search for density excesses from astrophysical point-like sources. No evidence for DC excesses for any source in an all-sky survey is reported. In addition, searches for muon excess correlated with the known binary periods of Cygnus X-3 and Hercules X-1, and searches for statistically significant bursting episodes from known gamma-ray sources are also proved negative. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 156. Ambrosio, M
    et al.
    Antolini, R
    Auriemma, G
    Bakari, D
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Search for diffuse neutrino flux from astrophysical sources with MACRO2003In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 19, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Many galactic and extragalactic astrophysical sources are currently considered promising candidates as high-energy neutrino emitters. Astrophysical neutrinos can be detected as upward-going muons produced in charged-current interactions with the medium surrounding the detector. The expected neutrino fluxes from various models start to dominate on the atmospheric neutrino background at neutrino energies above some tens of TeV. We present the results of a search for an excess of high-energy upward-going muons among the sample of data collected by MACRO during similar to5.8 years of effective running time. No significant evidence for this signal was found. As a consequence, an upper limit on the flux of upward-going muons from high-energy neutrinos was set at the level of 1.7 x 10(-14) cm(-2) s(-1) sr(-1). The corresponding upper limit for the diffuse neutrino flux was evaluated assuming a neutrino power law spectrum. Our result was compared with theoretical predictions and upper limits from other experiments. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 157.
    Ambrosio, M
    et al.
    Università di Napoli, Italy ; INFN, Italy.
    Antolini, R
    INFN, Italy.
    Auriemma, G
    Università di Roma “La Sapienza”, Italy ; INFN, Italy.
    Bakari, D
    Università di Bologna, Italy ; INFN, Italy ; University Mohamed I, Morocco.
    Baldini, A
    Università di Pisa, Italy ; INFN, Italy.
    Barbarino, G C
    Università di Napoli, Italy ; INFN, Italy.
    Barish, B C
    California Institute of Technology, USA.
    Battistoni, G
    INFN, Italy.
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Bellotti, R
    Università di Bari, Italy ; INFN, Italy.
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bloise, C
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Coutu, S
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    DiCredico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Guarino, F
    Gustavino, C
    Habig, A
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Manzoor, S
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Popa, V
    Reynoldson, J
    Ronga, F
    Rrhioua, A
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    A combined analysis technique for the search for fast magnetic monopoles with the MACRO detector2002In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 18, no 1, p. 27-41Article in journal (Refereed)
    Abstract [en]

    We describe a search method for fast moving (beta = v/c > 5 x 10(-3)) magnetic monopoles using simultaneously the scintillator, streamer tube and track-etch subdetectors of the MACRO apparatus. The first two subdetectors are used primarily for the identification of candidates while the track-etch one is used as the final tool for their rejection or confirmation. Using this technique, a first sample of more than two-years of data has been analyzed without any evidence of a magnetic monopole. We set a 90% CL upper limit to the local monopole flux of 1.5 x 10(-15) cm(-2) s(-1) sr(-1) in the velocity range 5 x 10(-3) less than or equal to beta less than or equal to 0.99 and for nucleon decay catalysis cross-section smaller than similar to1 mb (C) 2002 Elsevier Science B.V. All rights reserved.

  • 158. Ambrosio, M
    et al.
    Antolini, R
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Chiarusi, T
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kumar, A
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Manzoor, S
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Satriano, C
    Scapparone, E
    Scholberg, K
    Sioli, M
    Sirri, G
    Sitta, M S
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Moon and Sun shadowing effect in the MACRO detector2003In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 20, no 2, p. 145-156Article in journal (Refereed)
    Abstract [en]

    Using data collected by the MACRO experiment from 1989 to the end of its operations in 2000, we have studied in the underground muon flux the shadowing. effects due to both the Moon and the Sun. We have observed the shadow cast by the Moon at its apparent position with a significance of 6.5sigma. The Moon shadowing effect has been used to verify the pointing capability of the detector and to determine the instrument resolution for the search of muon excesses from any direction of the celestial sphere. The dependence of the effect on the geomagnetic field is clearly shown by splitting the data sample in day and night observations. The Sun shadow, observed with a significance of 4.6sigma is displaced by about 0.6degrees from its apparent position. In this case however the explanation resides in the configuration of the Solar and Interplanetary Magnetic Fields, which affect the propagation of cosmic ray particles between the Sun, and the Earth. The displacement of the Sun shadow with respect to the real Sun position has been used to establish an upper limit on the antimatter flux in cosmic rays of about 48% at 68% c.l. and primary energies of about 20 TeV. (C) 2003 Elsevier B.V. All rights reserved.

  • 159. Ambrosio, M
    et al.
    Antolini, R
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Chiarusi, T
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, A
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Maaroufi, F
    Mancarella, G
    Mandrioli, G
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Miller, L
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Satriano, C
    Scapparone, E
    Scholberg, K
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Togo, V
    Vakili, M
    Walter, C W
    Webb, R
    Search for the sidereal and solar diurnal modulations in the total MACRO muon data set2003In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 67, no 4, article id 042002Article in journal (Refereed)
    Abstract [en]

    We have analyzed 44.3M single muons collected by MACRO from 1991 through 2000 in 2145 live days of operation. We have searched for the solar diurnal, apparent sidereal, and pseudosidereal modulation of the underground muon rate by computing hourly deviations of the muon rate from 6 month averages. We find evidence for statistically significant modulations with the solar diurnal and the sidereal periods. The amplitudes of these modulations are <0.1%, and are at the limit of the detector statistics. The pseudosidereal modulation is not statistically significant. The solar diurnal modulation is due to the daily atmospheric temperature variations at 20 km, the altitude of primary cosmic ray interactions with the atmosphere; MACRO is the deepest experiment to report this result. The sidereal modulation is in addition to the expected Compton-Getting modulation due to solar system motion relative to the local standard of rest; it represents motion of the solar system with respect to the galactic cosmic rays toward the galactic plane.

  • 160. Ambrosio, M
    et al.
    Antolini, R
    Baldini, A
    Barbarino, G C
    Barish, B C
    Battistoni, G
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Bellotti, R
    Bemporad, C
    Bernardini, P
    Bilokon, H
    Bower, C
    Brigida, M
    Bussino, S
    Cafagna, F
    Calicchio, M
    Campana, D
    Carboni, M
    Caruso, R
    Cecchini, S
    Cei, F
    Chiarella, V
    Choudhary, B C
    Coutu, S
    Cozzi, M
    De Cataldo, G
    Dekhissi, H
    De Marzo, C
    De Mitri, I
    Derkaoui, J
    De Vincenzi, M
    Di Credico, A
    Erriquez, O
    Favuzzi, C
    Forti, C
    Fusco, P
    Giacomelli, G
    Giannini, G
    Giglietto, N
    Giorgini, M
    Grassi, M
    Grillo, H
    Guarino, F
    Gustavino, C
    Habig, A
    Hanson, K
    Heinz, R
    Iarocci, E
    Katsavounidis, E
    Katsavounidis, I
    Kearns, E
    Kim, H
    Kyriazopoulou, S
    Lamanna, E
    Lane, C
    Levin, D S
    Lipari, P
    Longley, N P
    Longo, M J
    Loparco, F
    Mancarella, G
    Mandrioli, G
    Margiotta, A
    Marini, A
    Martello, D
    Marzari-Chiesa, A
    Mazziotta, M N
    Michael, D G
    Monacelli, P
    Montaruli, T
    Monteno, M
    Mufson, S
    Musser, J
    Nicolo, D
    Nolty, R
    Orth, C
    Osteria, G
    Palamara, O
    Patera, V
    Patrizii, L
    Pazzi, R
    Peck, C W
    Perrone, L
    Petrera, S
    Pistilli, P
    Popa, V
    Raino, A
    Reynoldson, J
    Ronga, F
    Satraino, C
    Scapparone, E
    Scholberg, K
    Sciubba, A
    Serra, P
    Sioli, M
    Sirri, G
    Sitta, M
    Spinelli, P
    Spinetti, M
    Spurio, M
    Steinberg, R
    Stone, J L
    Sulak, L R
    Surdo, A
    Tarle, G
    Vakili, M
    Walter, C W
    Webb, R
    Measurement of the residual energy of muons in the Gran Sasso underground laboratories2003In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 19, no 3, p. 313-328Article in journal (Refereed)
    Abstract [en]

    The MACRO detector was located in the Hall B of the Gran Sasso underground laboratories under an average rock overburden of 3700 hg/cm(2). A transition radiation detector composed of three identical modules, covering a total horizontal area of 36 m(2), was installed inside the empty upper part of the detector in order to measure the residual energy of muons. This paper presents the measurement of the residual energy of single and double muons crossing the apparatus. Our data show that double muons are more energetic than single ones. This measurement is performed over a standard rock depth range from 3000 to 6500 hg/cm(2). (C) 2002 Elsevier Science B.V. All rights reserved.

  • 161.
    Andersson, Tom
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Inverse Compton gamma-rays from Markarian 421: A study of GeV and TeV emission from Mrk 421 based on Fermi-LAT and H.E.S.S. data2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis summarizes a senior project on the Active Galactic Nucleus (AGN) Markarian 421 (Mrk 421). Observations of Gev and TeV flux with Fermi Large Area Telescope (LAT) and High Energy Stereoscopic System (H.E.S.S.) were compared with previous reports and publications of flux analyses of the gamma-ray emission from Mrk 421. Power laws with exponential cutoffs made consistent fits to most SEDs in the GeV and TeV bands.

  • 162. Archambault, S.
    et al.
    Arlen, T.
    Aune, T.
    Behera, B.
    Beilicke, M.
    Benbow, W.
    Bird, R.
    Bouvier, A.
    Buckley, J. H.
    Bugaev, V.
    Byrum, K.
    Cesarini, A.
    Ciupik, L.
    Connolly, M. P.
    Cui, W.
    Errando, M.
    Falcone, A.
    Federici, S.
    Feng, Q.
    Finley, J. P.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gall, D.
    Gillanders, G. H.
    Griffin, S.
    Grube, J.
    Gyuk, G.
    Hanna, D.
    Holder, J.
    Hughes, G.
    Humensky, T. B.
    Kaaret, P.
    Kertzman, M.
    Khassen, Y.
    Kieda, D.
    Krawczynski, H.
    Krennrich, F.
    Kumar, S.
    Lang, M. J.
    Madhavan, A. S.
    Maier, G.
    Majumdar, P.
    McArthur, S.
    McCann, A.
    Millis, J.
    Moriarty, P.
    Mukherjee, R.
    O’Faoláin de Bhróithe, A.
    Ong, R. A.
    Otte, A. N.
    Park, N.
    Perkins, J. S.
    Pohl, M.
    Popkow, A.
    Prokoph, Heike
    DESY, Germany .
    Quinn, J.
    Ragan, K.
    Reyes, L. C.
    Reynolds, P. T.
    Richards, G. T.
    Roache, E.
    Saxon, D. B.
    Sembroski, G. H.
    Smith, A. W.
    Staszak, D.
    Telezhinsky, I.
    Theiling, M.
    Varlotta, A.
    Vassiliev, V. V.
    Vincent, S.
    Wakely, S. P.
    Weekes, T. C.
    Weinstein, A.
    Welsing, R.
    Williams, D. A.
    Zitzer, B.
    Collaboration, V E R I T A S
    Böttcher, M.
    Fegan, S. J.
    Fortin, P.
    Halpern, J. P.
    Kovalev, Y. Y.
    Lister, M. L.
    Liu, J.
    Pushkarev, A. B.
    Smith, P. S.
    Discovery of a New TeV Gamma-Ray Source: VER J0521+2112013In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 776, no 2, article id 69Article in journal (Refereed)
    Abstract [en]

    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 ± 0.13stat ± 0.78sys× 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 ~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.

  • 163. Archambault, S.
    et al.
    Aune, T.
    Behera, B.
    Beilicke, M.
    Benbow, W.
    Berger, K.
    Bird, R.
    Biteau, J.
    Bugaev, V.
    Byrum, K.
    Cardenzana, J. V.
    Cerruti, M.
    Chen, X.
    Ciupik, L.
    Connolly, M. P.
    Cui, W.
    Dumm, J.
    Errando, M.
    Falcone, A.
    Federici, S.
    Feng, Q.
    Finley, J. P.
    Fleischhack, H.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gillanders, G. H.
    Griffin, S.
    Griffiths, S. T.
    Grube, J.
    Gyuk, G.
    Hanna, D.
    Holder, J.
    Hughes, G.
    Humensky, T. B.
    Johnson, C. A.
    Kaaret, P.
    Kertzman, M.
    Khassen, Y.
    Kieda, D.
    Krawczynski, H.
    Krennrich, F.
    Kumar, S.
    Lang, M. J.
    Madhavan, A. S.
    Maier, G.
    McCann, A.
    Meagher, K.
    Moriarty, P.
    Mukherjee, R.
    Nieto, D.
    O’Faoláin de Bhróithe, A.
    Ong, R. A.
    Otte, A. N.
    Park, N.
    Pohl, M.
    Popkow, A.
    Prokoph, Heike
    DESY, Germany .
    Quinn, J.
    Ragan, K.
    Rajotte, J.
    Reyes, L. C.
    Reynolds, P. T.
    Richards, G. T.
    Roache, E.
    Sembroski, G. H.
    Shahinyan, K.
    Staszak, D.
    Telezhinsky, I.
    Tucci, J. V.
    Tyler, J.
    Varlotta, A.
    Vassiliev, V. V.
    Vincent, S.
    Wakely, S. P.
    Weinstein, A.
    Welsing, R.
    Wilhelm, A.
    Williams, D. A.
    Collaboration, V E R I T A S
    Ackermann, M.
    Ajello, M.
    Albert, A.
    Baldini, L.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Bregeon, J.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Cavazzuti, E.
    Charles, E.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cutini, S.
    D’Ammando, F.
    de Angelis, A.
    de Palma, F.
    Dermer, C. D.
    Digel, S. W.
    Di Venere, L.
    Drell, P. S.
    Favuzzi, C.
    Franckowiak, A.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Grenier, I. A.
    Guiriec, S.
    Jogler, T.
    Kuss, M.
    Larsson, S.
    Latronico, L.
    Longo, F.
    Loparco, F.
    Lubrano, P.
    Madejski, G. M.
    Mayer, M.
    Mazziotta, M. N.
    Michelson, P. F.
    Mizuno, T.
    Monzani, M. E.
    Morselli, A.
    Murgia, S.
    Nuss, E.
    Ohsugi, T.
    Ormes, J. F.
    Paneque, D.
    Perkins, J. S.
    Piron, F.
    Pivato, G.
    Rainò, S.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Ritz, S.
    Schaal, M.
    Sgrò, C.
    Siskind, E. J.
    Spinelli, P.
    Takahashi, H.
    Tibaldo, L.
    Tinivella, M.
    Troja, E.
    Vianello, G.
    Werner, M.
    Wood, M.
    Collaboration, Fermi LAT
    Deep Broadband Observations of the Distant Gamma-Ray Blazar PKS 1424+2402014In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 785, no 1, article id L16Article in journal (Refereed)
    Abstract [en]

    We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z ≥ 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 ± 0.3) × 10–7 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) × 10–7 photons m–2 s–1 above 120 GeV. The measured differential very high energy (VHE; E ≥ 100 GeV) spectral indices are Γ = 3.8 ± 0.3, 4.3 ± 0.6 and 4.5 ± 0.2 in 2009, 2011, and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than τ = 2, where it is postulated that any variability would be small and occur on timescales longer than a year if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics.

  • 164. Archambault, S.
    et al.
    Beilicke, M.
    Benbow, W.
    Berger, K.
    Bird, R.
    Bouvier, A.
    Buckley, J. H.
    Bugaev, V.
    Byrum, K.
    Cerruti, M.
    Chen, X.
    Ciupik, L.
    Connolly, M. P.
    Cui, W.
    Duke, C.
    Dumm, J.
    Errando, M.
    Falcone, A.
    Federici, S.
    Feng, Q.
    Finley, J. P.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gillanders, G. H.
    Griffin, S.
    Griffiths, S. T.
    Grube, J.
    Gyuk, G.
    Hanna, D.
    Holder, J.
    Hughes, G.
    Humensky, T. B.
    Kaaret, P.
    Kertzman, M.
    Khassen, Y.
    Kieda, D.
    Krawczynski, H.
    Lang, M. J.
    Madhavan, A. S.
    Maier, G.
    Majumdar, P.
    McArthur, S.
    McCann, A.
    Moriarty, P.
    Mukherjee, R.
    Nieto, D.
    O’Faoláin de Bhróithe, A.
    Ong, R. A.
    Otte, A. N.
    Pandel, D.
    Park, N.
    Perkins, J. S.
    Pohl, M.
    Popkow, A.
    Prokoph, Heike
    DESY, Germany .
    Quinn, J.
    Ragan, K.
    Rajotte, J.
    Reyes, L. C.
    Reynolds, P. T.
    Richards, G. T.
    Roache, E.
    Sembroski, G. H.
    Sheidaei, F.
    Smith, A. W.
    Staszak, D.
    Telezhinsky, I.
    Theiling, M.
    Tucci, J. V.
    Tyler, J.
    Varlotta, A.
    Vincent, S.
    Wakely, S. P.
    Weekes, T. C.
    Weinstein, A.
    Williams, D. A.
    Zitzer, B.
    Collaboration, V E R I T A S
    McCollough, M. L.
    Astrophysical Observatory, S.
    VERITAS Observations of the Microquasar Cygnus X-32013In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 779, no 2, article id 150Article in journal (Refereed)
    Abstract [en]

    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.

  • 165.
    Arias, M.
    et al.
    Univ Amsterdam, Netherlands.
    Vink, J.
    Univ Amsterdam, Netherlands;SRON Netherlands Inst Space Res, Netherlands.
    de Gasperin, F.
    Leiden Univ, Netherlands;Netherlands Inst Radio Astron, Netherlands.
    Salas, P.
    Leiden Univ, Netherlands.
    Oonk, J. B. R.
    Leiden Univ, Netherlands;Netherlands Inst Radio Astron, Netherlands.
    van Weeren, R. J.
    Leiden Univ, Netherlands.
    van Amesfoort, A. S.
    Netherlands Inst Radio Astron, Netherlands.
    Anderson, J.
    Helmholtz Zentrum Potsdam, Germany.
    Beck, R.
    Max Planck Inst Radio Astron, Germany.
    Bell, M. E.
    Univ Technol Sydney, Australia.
    Bentum, M. J.
    Netherlands Inst Radio Astron, Netherlands;Eindhoven Univ Technol, Netherlands.
    Best, P.
    Univ Edinburgh, UK.
    Blaauw, R.
    Netherlands Inst Radio Astron, Netherlands.
    Breitling, F.
    Leibniz Inst Astrophys Potsdam AIP, Germany.
    Broderick, J. W.
    Netherlands Inst Radio Astron, Netherlands.
    Brouw, W. N.
    Netherlands Inst Radio Astron, Netherlands;Kapteyn Astron Inst, Netherlands.
    Brueggen, M.
    Univ Hamburg, Germany.
    Butcher, H. R.
    Australian Natl Univ, Australia.
    Ciardi, B.
    Max Planck Inst Astrophys, Germany.
    de Geus, E.
    Netherlands Inst Radio Astron, Netherlands;SmarterVision BV, Netherlands.
    Deller, A.
    Netherlands Inst Radio Astron, Netherlands;Swinburne Univ Technol, Australia.
    van Dijk, P. C. G.
    Netherlands Inst Radio Astron, Netherlands.
    Duscha, S.
    Netherlands Inst Radio Astron, Netherlands.
    Eisloeffel, J.
    Thuringer Landessternwarte, Germany.
    Garrett, M. A.
    Leiden Univ, Netherlands;Univ Manchester, UK.
    Griessmeier, J. M.
    Univ Orleans, France.
    Gunst, A. W.
    Netherlands Inst Radio Astron, Netherlands.
    van Haarlem, M. P.
    Netherlands Inst Radio Astron, Netherlands.
    Heald, G.
    Netherlands Inst Radio Astron, Netherlands;Kapteyn Astron Inst, POB 800, NL-9700 AV Groningen, Netherlands.;CSIRO Astron & Space Sci, Australia.
    Hessels, J.
    Univ Amsterdam, Netherlands;Netherlands Inst Radio Astron, Netherlands.
    Horandel, J.
    Radboud Univ Nijmegen, Netherlands.
    Holties, H. A.
    Netherlands Inst Radio Astron, Netherlands.
    van der Horst, A. J.
    George Washington Univ, USA.
    Iacobelli, M.
    Netherlands Inst Radio Astron, Netherlands.
    Juette, E.
    Ruhr Univ Bochum, Germany.
    Krankowski, A.
    Univ Warmia & Mazury, Poland.
    van Leeuwen, J.
    Univ Amsterdam, Netherlands;Netherlands Inst Radio Astron, Netherlands.
    Mann, G.
    Leibniz Inst Astrophys Potsdam AIP, Germany.
    McKay-Bukowski, D.
    Univ Tromsö, Norway;STFC Rutherford Appleton Lab, UK.
    McKean, J. P.
    Netherlands Inst Radio Astron, Netherlands;Kapteyn Astron Inst, Netherlands.
    Mulder, H.
    Netherlands Inst Radio Astron, Netherlands.
    Nelles, A.
    Univ Calif Irvine, USA.
    Orru, E.
    Netherlands Inst Radio Astron, Netherlands.
    Paas, H.
    Univ Groningen, Netherlands.
    Pandey-Pommier, M.
    Observ Lyon, France.
    Pandey, V. N.
    Netherlands Inst Radio Astron, Netherlands;Kapteyn Astron Inst, Netherlands.
    Pekal, R.
    Poznan Supercomp & Networking Ctr PCSS, Poland.
    Pizzo, R.
    Netherlands Inst Radio Astron, Netherlands.
    Polatidis, A. G.
    Netherlands Inst Radio Astron, Netherlands.
    Reich, W.
    Max Planck Inst Radio Astron, Germany.
    Rottgering, H. J. A.
    Leiden Univ, Netherlands.
    Rothkaehl, H.
    Space Res Ctr PAS, Poland.
    Schwarz, D. J.
    Univ Bielefeld, Germany.
    Smirnov, O.
    Rhodes Univ, South Africa;SKA South Africa, South Africa.
    Soida, M.
    Jagiellonian Univ, Poland.
    Steinmetz, M.
    Leibniz Inst Astrophys Potsdam AIP, Germany.
    Tagger, M.
    Univ Orleans, France.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Toribio, M. C.
    Leiden Univ,Netherlands;Netherlands Inst Radio Astron, Netherlands.
    Vocks, C.
    Leibniz Inst Astrophys Potsdam AIP, Germany.
    van der Wiel, M. H. D.
    Netherlands Inst Radio Astron, Netherlands.
    Wijers, R. A. M. J.
    Univ Amsterdam, Netherlands.
    Wucknitz, O.
    Max Planck Inst Radio Astron, Germany.
    Zarka, P.
    Observ Paris, France;Observ Paris, France.
    Zucca, P.
    Netherlands Inst Radio Astron, Netherlands.
    Low-frequency radio absorption in Cassiopeia A2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 612, article id A110Article in journal (Refereed)
    Abstract [en]

    Context. Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be studied: through emission in the infrared, the radio-active decay of Ti-44, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper. Aims. Free-free absorption processes are affected by the mass, geometry, temperature, and ionisation conditions in the absorbing gas. Observations at the lowest radio frequencies can constrain a combination of these properties. Methods. We used Low Frequency Array (LOFAR) Low Band Antenna observations at 30-77 MHz and Very Large Array (VLA) L-band observations at 1-2 GHz to fit for internal absorption as parametrised by the emission measure. We simultaneously fit multiple UV-matched images with a common resolution of 17 '' (this corresponds to 0.25 pc for a source at the distance of Cas A). The ample frequency coverage allows us separate the relative contributions from the absorbing gas, the unabsorbed front of the shell, and the absorbed back of the shell to the emission spectrum. We explored the effects that a temperature lower than the similar to 100-500 K proposed from infrared observations and a high degree of clumping can have on the derived physical properties of the unshocked material, such as its mass and density. We also compiled integrated radio flux density measurements, fit for the absorption processes that occur in the radio band, and considered their effect on the secular decline of the source. Results. We find a mass in the unshocked ejecta of M = 2.95 +/- 0.48 M-circle dot for an assumed gas temperature of T = 100 K. This estimate is reduced for colder gas temperatures and, most significantly, if the ejecta are clumped. We measure the reverse shock to have a radius of 114 '' +/- 6 '' and be centred at 23:23:26, +58:48:54 (J2000). We also find that a decrease in the amount of mass in the unshocked ejecta (as more and more material meets the reverse shock and heats up) cannot account for the observed low-frequency behaviour of the secular decline rate. Conclusions. To reconcile our low-frequency absorption measurements with models that reproduce much of the observed behaviour in Cas A and predict little mass in the unshocked ejecta, the ejecta need to be very clumped or the temperature in the cold gas needs to be low (similar to 10 K). Both of these options are plausible and can together contribute to the high absorption value that we find.

  • 166. Arlen, T.
    et al.
    Aune, T.
    Beilicke, M.
    Benbow, W.
    Bouvier, A.
    Buckley, J. H.
    Bugaev, V.
    Byrum, K.
    Cannon, A.
    Cesarini, A.
    Ciupik, L.
    Collins-Hughes, E.
    Connolly, M. P.
    Cui, W.
    Dickherber, R.
    Dumm, J.
    Falcone, A.
    Federici, S.
    Feng, Q.
    Finley, J. P.
    Finnegan, G.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gall, D.
    Godambe, S.
    Griffin, S.
    Grube, J.
    Gyuk, G.
    Holder, J.
    Huan, H.
    Hughes, G.
    Humensky, T. B.
    Imran, A.
    Kaaret, P.
    Karlsson, N.
    Kertzman, M.
    Khassen, Y.
    Kieda, D.
    Krawczynski, H.
    Krennrich, F.
    Lee, K.
    Madhavan, A. S.
    Maier, G.
    Majumdar, P.
    McArthur, S.
    McCann, A.
    Moriarty, P.
    Mukherjee, R.
    Nelson, T.
    O’Faoláin de Bhróithe, A.
    Ong, R. A.
    Orr, M.
    Otte, A. N.
    Park, N.
    Perkins, J. S.
    Pohl, M.
    Prokoph, Heike
    DESY, Germany.
    Quinn, J.
    Ragan, K.
    Reyes, L. C.
    Reynolds, P. T.
    Roache, E.
    Ruppel, J.
    Saxon, D. B.
    Schroedter, M.
    Sembroski, G. H.
    Skole, C.
    Smith, A. W.
    Telezhinsky, I.
    Tesić, G.
    Theiling, M.
    Thibadeau, S.
    Tsurusaki, K.
    Varlotta, A.
    Vivier, M.
    Wakely, S. P.
    Ward, J. E.
    Weinstein, A.
    Welsing, R.
    Williams, D. A.
    Zitzer, B.
    Pfrommer, C.
    Pinzke, A.
    Constraints on Cosmic Rays, Magnetic Fields, and Dark Matter from Gamma-Ray Observations of the Coma Cluster of Galaxies with VERITAS and Fermi2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 757, no 2, article id 123Article in journal (Refereed)
    Abstract [en]

    We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semimajor (semiminor) axis 030 (024) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N 0(E/3 TeV)–Γ, with a differential spectral index of Γ = 2.2 ± 0.2stat ± 0.3sys, and normalization N 0 = (9.1 ± 1.3stat ± 1.7sys× 10–14 cm–2 s–1 TeV–1. The integral flux, F γ = 4.0 ×10–12 erg cm–2 s–1 above 1 TeV, corresponds to 0.2% of the pulsar spin-down power at 1.4 kpc. The energetics, colocation with the SNR, and the relatively small extent of the TeV emission strongly argue for the PWN origin of the TeV photons. We consider the origin of the TeV emission in CTA 1.

  • 167. Arlen, T.
    et al.
    Aune, T.
    Beilicke, M.
    Benbow, W.
    Bouvier, A.
    Buckley, J. H.
    Bugaev, V.
    Cesarini, A.
    Ciupik, L.
    Connolly, M. P.
    Cui, W.
    Dickherber, R.
    Dumm, J.
    Errando, M.
    Falcone, A.
    Federici, S.
    Feng, Q.
    Finley, J. P.
    Finnegan, G.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gall, D.
    Griffin, S.
    Grube, J.
    Gyuk, G.
    Hanna, D.
    Holder, J.
    Humensky, T. B.
    Kaaret, P.
    Karlsson, N.
    Kertzman, M.
    Khassen, Y.
    Kieda, D.
    Krawczynski, H.
    Krennrich, F.
    Maier, G.
    Moriarty, P.
    Mukherjee, R.
    Nelson, T.
    O’Faoláin de Bhróithe, A.
    Ong, R. A.
    Orr, M.
    Park, N.
    Perkins, J. S.
    Pichel, A.
    Pohl, M.
    Prokoph, Heike
    DESY, Germany .
    Quinn, J.
    Ragan, K.
    Reyes, L. C.
    Reynolds, P. T.
    Roache, E.
    Saxon, D. B.
    Schroedter, M.
    Sembroski, G. H.
    Staszak, D.
    Telezhinsky, I.
    Te\v sić, G.
    Theiling, M.
    Tsurusaki, K.
    Varlotta, A.
    Vincent, S.
    Wakely, S. P.
    Weekes, T. C.
    Weinstein, A.
    Welsing, R.
    Williams, D. A.
    Zitzer, B.
    Collaboration, V E R I T A S
    Jorstad, S. G.
    MacDonald, N. R.
    Marscher, A. P.
    Smith, P. S.
    Walker, R. C.
    Hovatta, T.
    Richards, J.
    Max-Moerbeck, W.
    Readhead, A.
    Lister, M. L.
    Kovalev, Y. Y.
    Pushkarev, A. B.
    Gurwell, M. A.
    Lähteenmäki, A.
    Nieppola, E.
    Tornikoski, M.
    Järvelä, E.
    Rapid TeV Gamma-Ray Flaring of BL Lacertae2013In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 762, no 2, article id 92Article in journal (Refereed)
    Abstract [en]

    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) × 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.

  • 168. Atwood, W. B.
    et al.
    Abdo, A. A.
    Ackermann, M.
    Althouse, W.
    Anderson, B.
    Axelsson, M.
    Baldini, L.
    Ballet, J.
    Band, D. L.
    Barbiellini, G.
    Bartelt, J.
    Bastieri, D.
    Baughman, B. M.
    Bechtol, K.
    Bederede, D.
    Bellardi, F.
    Bellazzini, R.
    Berenji, B.
    Bignami, G. F.
    Bisello, D.
    Bissaldi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bogart, J. R.
    Bonamente, E.
    Bonnell, J.
    Borgland, A. W.
    Bouvier, A.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Busetto, G.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Carius, Staffan
    University of Kalmar, Department of Technology.
    Carlson, P.
    Casandjian, J. M.
    Cavazzuti, E.
    Ceccanti, M.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Chipaux, R.
    Cillis, A. N.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Condamoor, S.
    Conrad, J.
    Corbet, R.
    Corucci, L.
    Costamante, L.
    Cutini, S.
    Davis, D. S.
    Decotigny, D.
    DeKlotz, M.
    Dermer, C. D.
    De Angelis, A.
    Digel, S. W.
    Silva, Edce
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Edmonds, Y.
    Fabiani, D.
    Farnier, C.
    Favuzzi, C.
    Flath, D. L.
    Fleury, P.
    Focke, W. B.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Gentit, F. X.
    Germani, S.
    Giebels, B.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M. H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Haller, G.
    Harding, A. K.
    Hart, P. A.
    Hays, E.
    Healey, S. E.
    Hirayama, M.
    Hjalmarsdotter, L.
    Horn, R.
    Hughes, R. E.
    Johannesson, G.
    Johansson, G.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, T. J.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kavelaars, A.
    Kawai, N.
    Kelly, H.
    Kerr, M.
    Klamra, W.
    Knodlseder, J.
    Kocian, M. L.
    Komin, N.
    Kuehn, F.
    Kuss, M.
    Landriu, D.
    Latronico, L.
    Lee, B.
    Lee, S. H.
    Lemoine-Goumard, M.
    Lionetto, A. M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Marangelli, B.
    Massai, M. M.
    Mazziotta, M. N.
    McEnery, J. E.
    Menon, N.
    Meurer, C.
    Michelson, P. F.
    Minuti, M.
    Mirizzi, N.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Moretti, E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Nishino, S.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paccagnella, A.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pearce, M.
    Pepe, M.
    Perazzo, A.
    Pesce-Rollins, M.
    Picozza, P.
    Pieri, L.
    Pinchera, M.
    Piron, F.
    Porter, T. A.
    Poupard, L.
    Raino, S.
    Rando, R.
    Rapposelli, E.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Reyes, L. C.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Romani, R. W.
    Roth, M.
    Russell, J. J.
    Ryde, F.
    Sabatini, S.
    Sadrozinski, H. F. W.
    Sanchez, D.
    Sander, A.
    Sapozhnikov, L.
    Parkinson, P. M. S.
    Scargle, J. D.
    Schalk, T. L.
    Scolieri, G.
    Sgro, C.
    Share, G. H.
    Shaw, M.
    Shimokawabe, T.
    Shrader, C.
    Sierpowska-Bartosik, A.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Starck, J. L.
    Stephens, T. E.
    Strickman, M. S.
    Strong, A. W.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Tenze, A.
    Tether, S.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Tibolla, O.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Turri, M.
    Usher, T. L.
    Vilchez, N.
    Vitale, V.
    Wang, P.
    Watters, K.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Ziegler, M.
    THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 697, no 2, p. 1071-1102Article in journal (Refereed)
    Abstract [en]

    The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view (FoV), high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. The LAT was built by an international collaboration with contributions from space agencies, high-energy particle physics institutes, and universities in France, Italy, Japan, Sweden, and the United States. This paper describes the LAT, its preflight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4 x 4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 (x, y) tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an eight-layer hodoscopic configuration with a total depth of 8.6 radiation lengths, giving both longitudinal and transverse information about the energy deposition pattern. The calorimeter's depth and segmentation enable the high-energy reach of the LAT and contribute significantly to background rejection. The aspect ratio of the tracker (height/width) is 0.4, allowing a large FoV (2.4 sr) and ensuring that most pair-conversion showers initiated in the tracker will pass into the calorimeter for energy measurement. Data obtained with the LAT are intended to (1) permit rapid notification of high-energy gamma-ray bursts and transients and facilitate monitoring of variable sources, (2) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (3) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (4) localize point sources to 0.3-2 arcmin, (5) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (6) measure the diffuse isotropic gamma-ray background up to TeV energies, and (7) explore the discovery space for dark matter.

  • 169.
    Baan, Willem
    et al.
    Linnaeus University, Faculty of Technology, Department of computer science and media technology (CM), Department of Computer Science. ASTRON, Netherlands;Shanghai Astron Observ, Peoples Republic of China.
    Loenen, A. F.
    ASTRON, Netherlands;Kapteyn Astron Inst, Netherlands.
    Spaans, M.
    Kapteyn Astron Inst, Netherlands.
    Multimolecular studies of Galactic star-forming regions2014In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 445, no 4, p. 3331-3344Article in journal (Refereed)
    Abstract [en]

    Molecular emission-line observations of isolated Galactic star-forming regions are used to model the physical properties of the molecular interstellar medium in these systems. Observed line ratios are compared with the results predicted by models that incorporate gas-phase chemistry and the heating by stellar radiation and non-radiative feedback processes. The line ratios of characteristic tracer molecules may be interpreted using the contributions of two distinct components: a cold (40-50 K) and high-density (105-105.5 cm(-3)) photon-dominated region (PDR) with a nominal UV flux density and a warm (similar to 300 K) mechanical heating-dominated region (MHDR) with a slightly lower density (10(4.5)-10(5) cm(-3)). The relative contributions of these structural components are used to model the observed line ratios. Ionized species may be better modelled by adopting an increase of the cosmic ray flux towards the Galactic Centre and the sulphur abundance should depleted by a factor of 200-400 relative to solar values. The line ratios of the Galactic sample are found to be very similar to those of the integrated signature of prominent (ultra) luminous IR Galaxies. The PDRs and MHDRs in the isolated Galactic regions may be modelled with slightly higher mean densities than in extragalactic systems and a higher MHDR temperature resulting from non-radiative mechanical heating. Multimolecular studies are effective in determining the physical and chemical properties of star formation regions by using characteristic line ratios to diagnose their environment. The addition of more molecular species will reduce the existing modelling redundancy.

  • 170. Barbiellini, G.
    et al.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Blandford, R. D.
    Borgland, A. W.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Cavazzuti, E.
    Cecchi, C.
    Chaves, R. C. G.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    D’Ammando, F.
    de Angelis, A.
    Dermer, C. D.
    Digel, S. W.
    Silva, E. d. C. e.
    Drell, P. S.
    Drlica-Wagner, A.
    Favuzzi, C.
    Focke, W. B.
    Franckowiak, A.
    Fukazawa, Y.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Germani, S.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Hadasch, D.
    Hayashida, M.
    Hays, E.
    Hughes, R. E.
    Jackson, M. S.
    Jogler, T.
    Knödlseder, J.
    Kuss, M.
    Lande, J.
    Larsson, S.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Mazziotta, M. N.
    Mehault, J.
    Michelson, P. F.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nemmen, R.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orienti, M.
    Orlando, E.
    Paneque, D.
    Perkins, J. S.
    Piron, F.
    Pivato, G.
    Prokhorov, Dmitry
    Stanford Univ, USA.
    Rainò, S.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Ritz, S.
    Romoli, C.
    Sánchez-Conde, M.
    Sanchez, D. A.
    Sgrò, C.
    Siskind, E. J.
    Spandre, G.
    Spinelli, P.
    Takahashi, H.
    Tanaka, T.
    Tibaldo, L.
    Tinivella, M.
    Tosti, G.
    Troja, E.
    Usher, T. L.
    Vandenbroucke, J.
    Vasileiou, V.
    Vianello, G.
    Vitale, V.
    Waite, A. P.
    Winer, B. L.
    Wood, K. S.
    Yang, Z.
    Fermi Large Area Telescope Observations of Blazar 3C 279 Occultations by the Sun2014In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 784, no 2, article id 118Article in journal (Refereed)
    Abstract [en]

    Observations of occultations of bright. gamma-ray sources by the Sun may reveal predicted pair halos around blazars and/or new physics, such as, e.g., hypothetical light dark matter particles-axions. We use Fermi Gamma-Ray Space Telescope (Fermi) data to analyze four occultations of blazar 3C 279 by theSun on October 8 each year from 2008 to 2011. A combined analysis of the observations of these occultations allows a point-like source at the position of 3C279 to be detected with significance of approximate to 3 sigma, but does not reveal any significant excess over the flux expected from the quiescent Sun.The likelihood ratio test rules out complete transparency of the Sun to the blazar. gamma-ray emission at a 3s confidence level.

  • 171.
    Battistoni, G
    et al.
    INFN Sez. di Milano, Italy.
    Becherini, Yvonne
    Universita’ di Bologna, Italy.
    Cecchini, S
    Universita’ di Bologna, Italy ; INAF/IASF Sez. di Bologna, Italy.
    Cozzi, M
    Universita’ di Bologna, Italy.
    Dekhissi, H
    Universita’ di Bologna, Italy ; University Mohamed 1st, Morocco.
    Esposito, L.
    Universita’ di Bologna, Italy.
    Giacomelli, G
    Universita’ di Bologna, Italy.
    Giorgini, M
    Universita’ di Bologna, Italy.
    Mandrioli, G
    Universita’ di Bologna, Italy.
    Manzoor, S
    Universita’ di Bologna, Italy.
    Margiotta, A
    Universita’ di Bologna, Italy.
    Patrizii, L
    Universita’ di Bologna, Italy.
    Popa, V
    Universita’ di Bologna, Italy ; ISS, Romania.
    Sioli, M
    Universita’ di Bologna, Italy.
    Sirri, G
    Universita’ di Bologna, Italy.
    Spurio, M
    Universita’ di Bologna, Italy.
    Togo, V
    Universita’ di Bologna, Italy.
    Search for exotic contributions to atmospheric neutrino oscillations2005In: 29th International Cosmic Ray Conference: August 3 - 10, 2005, Pune, India, Mumbai: Tata Institute of Fundamental Research , 2005, p. 171-174Conference paper (Other academic)
    Abstract [en]

    The energy spectrum of neutrino-induced upward-going muons in MACRO was analysed in terms of relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of v(mu) -> v(tau) transitions. The data disfavor these possibilities even at a sub-dominant level; stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter vertical bar Delta v vertical bar < 6 x 10(-24) at sin 2 theta(v) = 0 and vertical bar Delta v vertical bar < 2.5 divided by 5 x 10(-26) at sin 2 theta(v) = +/- 1. The limits can be re-interpreted as bounds on the Equivalence Principle violation parameters.

  • 172. Battistoni, G
    et al.
    Becherini, Yvonne
    Università di Bologna, Italy ; INFN, Italy.
    Cecchini, S
    Cozzi, M
    Dekhissi, H
    Esposito, L S
    Giacomelli, G
    Giorgini, M
    Mandrioli, G
    Manzoor, S
    Margiotta, A
    Patrizii, L
    Popa, V
    Sioli, M
    Sirri, G
    Spurio, M
    Togo, V
    Search for a Lorentz invariance violation contribution in atmospheric neutrino oscillations using MACRO data2005In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 615, no 1-2, p. 14-18Article in journal (Refereed)
    Abstract [en]

    The energy spectrum of neutrino-induced upward-going muons in MACRO has been analysed in terms of relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of v(u) -> v(tau) transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter vertical bar Delta v vertical bar < 6 x 10(-24) at sin2 theta(v) = 0 and vertical bar Delta(v)vertical bar < 2.5-5 x 10(-26) at sin 2 theta(v) = +/- 1. These limits can also be re-interpreted as upper bounds on the parameters describing violation of the equivalence principle. (c) 2005 Elsevier B.V. All rights reserved.

  • 173.
    Becherini, Yvonne
    Dipartimento di Fisica dell’Universita’ di Bologna.
    ANTARES: Software organisation, reconstruction, performance studies2006In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 567, no 2, p. 477-479Article in journal (Refereed)
    Abstract [en]

    The ANTARES Collaboration is building an underwater neutrino telescope in the Mediterranean sea. The first full 480m line was connected to the shore station in March 2006. The full Monte Carlo simulation chain and offline software structure of the experiment is presented. The offline software structure consists of two main parts: the first concerns the generation of the Monte Carlo events in the detector and the cligitisation and filtering of the signals, while the second concerns offline event reconstruction of both Monte Carlo events and real data. The expected performances of the detector obtained from this accurate simulation procedure are also presented and discussed. (c) 2006 Elsevier B.V. All rights reserved.

  • 174.
    Becherini, Yvonne
    University of Bologna.
    The ANTARES neutrino telescope2003In: Neutrino Physics / [ed] Bellotti, E; Declais, Y; Strolin, P; Zanotti, L, Amsterdam: IOS Press, 2003, Vol. 152, p. 275-279Conference paper (Other academic)
  • 175.
    Becherini, Yvonne
    et al.
    University of Paris Diderot .
    Boisson, C.
    Cerruti, M.
    Discovery of VHE gamma-ray emission from the very distant BL Lac KUV00311-1938 by HESS2012In: HIGH ENERGY GAMMA-RAY ASTRONOMY, American Institute of Physics (AIP), 2012, p. 490-493Conference paper (Refereed)
    Abstract [en]

    The observed spectra of very-high-energy (VHE) blazars may be deformed by gamma-gamma absorption onto the Extra-galactic Background Light (EBL) or, more speculatively, by photon-axion oscillations. As the resulting imprint on observed spectral characteristics may be redshift-dependent, it is important to enrich the catalogue of VHE high-redshift blazars. HESS-II [1], with its low-energy threshold and enhanced E > 100 GeV sensitivity, will be a major instrument in this field of study. While awaiting this new phase of the experiment, H. E. S. S. observed the very distant BL Lac KUV00311 - 1938 in a multi-year campaign, leading to the discovery of its VHE gamma-ray emission with a significance of 5.1 standard deviations. The detection of this source has been possible thanks to an enhanced low-energy sensitivity of recent-developed analysis techniques for IACTs (Paris-MVA) and a full refurbishment which markedly lowered the overall analysis threshold. The evaluation of the redshift of this source is difficult, due to the weakness of the absorption lines in the optical spectrum. A first attempt to evaluate this redshift was performed by [2], and [3], where a value of 0.61 was quoted with a question mark. More recently, [4] used the data from the X-Shooter spectrograph operating on the VLT to estimate a solid lower limit on the redshift of the source of z > 0.506, confirming that KUV00311 - 1938 is the farthest BL Lac ever detected at VHE.

  • 176.
    Becherini, Yvonne
    et al.
    Università di Bologna, Italy ; INFN, Italy.
    Cecchini, S
    Chiarusi, T
    Cozzi, M
    Dekhissi, H
    Derkaoui, J
    Esposito, L S
    Giacomelli, G
    Giorgini, M
    Giglietto, N
    Maaroufi, F
    Mandrioli, G
    Margiotta, A
    Manzoor, S
    Patrizii, L
    Popa, V
    Sioli, M
    Sirri, G
    Spurio, M
    Togo, V
    Time correlations of high energy muons in an underground detector2005In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 23, no 3, p. 341-348Article in journal (Refereed)
    Abstract [en]

    We present the result of a search for correlations in the arrival times of high energy muons collected from 1995 till 2000 with the streamer tube system of the complete MACRO detector at the underground Gran Sasso Lab. Large samples of single muons (8.6 million), double muons (0.46 million) and multiple muons with multiplicities from 3 to 6 (0.08 million) were selected. These samples were used to search for time correlations of cosmic ray particles coming from the whole upper hemisphere or from selected space cones. The results of our analyses confirm with high statistics a random arrival time distribution of high energy cosmic rays. (c) 2005 Elsevier B.V. All rights reserved.

  • 177.
    Becherini, Yvonne
    et al.
    University of Bologna, Italy ; INFN Bologna, Italy.
    Cecchini, S
    University of Bologna, Italy ; INAF/IASF Sez. di Bologna, Italy.
    Cozzi, M
    University of Bologna, Italy.
    Dekhissi, H
    University of Bologna, Italy ; University Mohamed 1st, Morocco.
    Derkaoui, J
    University Mohamed 1st, Morocco.
    Giacomelli, G
    University of Bologna, Italy.
    Giorgini, M
    University of Bologna, Italy.
    Maaroufi, F
    University Mohamed 1st, Morocco.
    Mandrioli, G
    University of Bologna, Italy.
    Margiotta, A
    University of Bologna, Italy.
    Manzoor, S
    University of Bologna, Italy ; PRD, PINSTECH, Pakistan.
    Moussa, A
    University Mohamed 1st, Morocco.
    Patrizii, L
    University of Bologna, Italy.
    Popa, V
    University of Bologna, Italy ; ISS, Romania.
    Sioli, M
    University of Bologna, Italy.
    Sirri, G
    University of Bologna, Italy.
    Spurio, M
    University of Bologna, Italy.
    Togo, V
    University of Bologna, Italy.
    Time variations in the deep underground muon flux measured by MACRO2005In: 29th International Cosmic Ray Conference: August 3 - 10, 2005, Pune, India, Mumbai: Tata Institute of Fundamental Research , 2005, p. 157-160Conference paper (Other academic)
    Abstract [en]

    More than 30 million high-energy muons collected with the MACRO detector at the underground Gran Sasso Laboratory have been used to search for flux variations of different nature. Two kinds of studies were carried out: search for periodical variations and for the occurrence of clusters of events. Different analysis methods, including Lomb-Scargle spectral analysis and scan statistics have been applied to the data.

  • 178.
    Becherini, Yvonne
    et al.
    University of Bologna.
    Collaboration, A. N. T. A. R. E. S.
    Status report of the ANTARES experiment2006In: Taup 2005: Proceedings of the Ninth International Conference on Topics in Astroparticle and Underground Physics, 2006, p. 444-446Conference paper (Refereed)
    Abstract [en]

    The ANTARES Collaboration is building an underwater neutrino telescope in the Mediterranean sea. The telescope is designed to search for high energy (E > I TeV) galactic and extra-galactic neutrino sources, but could also be sensitive to neutrinos originating from the decay of neutralino and exotic particles. The detector is a 3-dimensional array of photomultipliers located at a depth of 2500 m, 40 km from the La Seyne sur Mer shore (near Toulon, France). During the year 2005 a full scale test line and an instrumented line have been successfully operated. In the winter '05-'06 the first full 480 m line will be deployed and connected to the shore station.

  • 179.
    Becherini, Yvonne
    et al.
    Paris Diderot University, France ; École Polytechnique, France.
    Djannati-Atai, A.
    Paris Diderot University, France.
    Marandon, V.
    Paris Diderot University, France.
    Punch, Michael
    Paris Diderot University, France.
    Pita, S.
    Paris Diderot University, France.
    A new analysis strategy for detection of faint gamma-ray sources with Imaging Atmospheric Cherenkov Telescopes2011In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 34, no 12, p. 858-870Article in journal (Refereed)
    Abstract [en]

    A new background rejection strategy for gamma-ray astrophysics with stereoscopic Imaging Atmospheric Cherenkov Telescopes (IACT), based on Monte Carlo (MC) simulations and real background data from the H.E.S.S. [High Energy Stereoscopic System, see [1].] experiment, is described. The analysis is based on a multivariate combination of both previously-known and newly-derived discriminant variables using the physical shower properties, as well as its multiple images, for a total of eight variables. Two of these new variables are defined thanks to a new energy evaluation procedure, which is also presented here. The method allows an enhanced sensitivity with the current generation of ground-based Cherenkov telescopes to be achieved, and at the same time its main features of rapidity and flexibility allow an easy generalization to any type of IACT. The robustness against Night Sky Background (NSB) variations of this approach is tested with MC simulated events. The overall consistency of the analysis chain has been checked by comparison of the real gamma-ray signal obtained from H.E.S.S. observations with MC simulations and through reconstruction of known source spectra. Finally, the performance has been evaluated by application to faint H.E.S.S. sources. The gain in sensitivity as compared to the best standard Hillas analysis ranges approximately from 1.2 to 1.8 depending on the source characteristics, which corresponds to an economy in observation time of a factor 1.4 to 3.2. (C) 2011 Elsevier B.V. All rights reserved.

  • 180.
    Becherini, Yvonne
    et al.
    University of Paris Diderot.
    Djannati-Atai, A.
    Punch, M.
    Univ Paris Diderot, APC, AstroParticule & Cosmology, CNRS,IN2P3,CEA,Irfu, Observ Paris,Sorbonne Paris C, 10 Rue Alice Domon & Leonie Duquet, F-75205 Paris 13, France.
    Bernloehr, K.
    Ehlert, S.
    Masbou, J.
    Moulin, E.
    Arribas, M. Paz
    HESS-II reconstruction strategy and performance in the low-energy (20-150 GeV) domain2009In: HIGH ENERGY GAMMA-RAY ASTRONOMY / [ed] Aharonian, FA; Hofmann, W; Rieger, FM, American Institute of Physics (AIP), 2009, p. 738-741Conference paper (Refereed)
    Abstract [en]

    In mid-2009 a notable upgrade of the H.E.S.S. telescope system will take place: a new telescope with a 600 m(2) mirror area and very-high-resolution camera (0.07 degrees) will be positioned at the centre of the present configuration, with the aim of lowering the threshold and enhance its sensitivity in the 100 GeV to several TeV energy range. HESS-II will permit the investigation of the lower energy gamma-ray spectra in various cosmic accelerators, giving information on the origin of the gamma-rays observed, and will detect AGNs with a redshift greater than 0.2 (being less affected by absorption by Extragalactic Background Light - EBL - in this energy range) and will search for new classes of very high energy gamma-ray emitters (pulsars, microquasars, GRB, and dark matter candidates).

  • 181.
    Becherini, Yvonne
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Farnier, Christian
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Stockholms universitet.
    Prokhorov, Dmitry
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Punch, Michael
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Université Paris Diderot, France.
    Abbott, B. P.
    LIGO, California Institute of Technology, USA.
    Abbott, R.
    LIGO, California Institute of Technology, USA.
    Abbott, T. D.
    Louisiana State University, USA.
    Acernese, F.
    Università di Salerno, Italy;INFN, Italy.
    Ackley, K.
    University of Florida, USA;OzGrav, Australia.
    Adams, C.
    LIGO Livingston Observatory, USA.
    Multi-messenger Observations of a Binary Neutron Star Merger2017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 48, no 2, article id L12Article in journal (Refereed)
    Abstract [en]

    On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of similar to 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of 40(-8)(+8) Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M-circle dot. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at similar to 40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over similar to 10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position similar to 9 and similar to 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

  • 182.
    Becherini, Yvonne
    et al.
    University of Paris Diderot .
    Khelifi, B.
    Pita, S.
    Punch, Michael
    Univ Paris Diderot, APC, AstroParticule & Cosmology, CNRS,IN2P3,CEA,Irfu, Observ Paris,Sorbonne Paris C, 10 Rue Alice Domon & Leonie Duquet, F-75205 Paris 13, France.
    Advanced analysis and event reconstruction for the CTA Observatory2012In: HIGH ENERGY GAMMA-RAY ASTRONOMY, American Institute of Physics (AIP), 2012, p. 769-772Conference paper (Refereed)
    Abstract [en]

    The planned Cherenkov Telescope Array (CTA) is a future observatory for very-high-energy (VHE) gamma-ray astronomy composed of one site per hemisphere [1]. It aims at 10 times better sensitivity, a better angular resolution and wider energy coverage than current installations such as H.E.S.S., MAGIC and VERITAS. In order to achieve this level of performance, both the design of the telescopes and the analysis algorithms are being studied and optimized within the CTA Monte-Carlo working group. Here, we present ongoing work on the data analysis for both the event reconstruction (energy, direction) and gamma/hadron separation, carried out within the HAP (H.E.S.S. Analysis Package) software framework of the H.E.S.S. collaboration, for this initial study. The event reconstruction uses both Hillas-parameter-based algorithms and an improved version of the 3D-Model algorithm [2]. For the gamma/hadron discrimination, original and robust discriminant variables are used and treated with Boosted Decision Trees (BDTs) in the TMVA [3] (Toolkit for Multivariate Data Analysis) framework. With this advanced analysis, known as Paris-MVA [4], the sensitivity is improved by a factor of similar to 2 in the core range of CTA relative to the standard analyses. Here we present the algorithms used for the reconstruction and discrimination, together with the resulting performance characteristics, with good confidence, since the method has been successfully applied for H.E.S.S.

  • 183.
    Becherini, Yvonne
    et al.
    Ecole Polytechnique.
    Punch, Michael
    Univ Paris Diderot, APC, AstroParticule & Cosmology, CNRS,IN2P3,CEA,Irfu, Observ Paris,Sorbonne Paris C, 10 Rue Alice Domon & Leonie Duquet, F-75205 Paris 13, France.
    Performance of HESS-II in multi-telescope mode with a multi-variate analysis2012In: High energy gamma-ray astronomy, American Institute of Physics (AIP), 2012, p. 741-744Conference paper (Refereed)
    Abstract [en]

    The second phase of H. E. S. S. is being commissioned and will start physics data-taking in Autumn 2012. The 4-telescope configuration is now enriched with a new very-large Cherenkov telescope (VLCT) at the centre of the array. The similar to 600m(2) mirror area and high-resolution camera of the VLCT will permit to lower the energy threshold to about 30GeV in the single-telescope mode, opening a new observational window to a large number of new high-energy phenomena. Adding the VLCT also enhances the detection sensitivity in the multi-telescope mode. The performance in this latter data-taking mode of HESS-II with the advanced analysis procedure called Paris-MVA has been studied in order to understand the achievable low-energy sensitivity and preliminary results are shown here. The Monte Carlo (MC) simulations, the gamma-ray reconstruction procedures and the analysis strategy used to obtain the resulting improvement in sensitivity by adding the VLCT - of about a factor of similar to 2 at low energy - will be discussed.

  • 184.
    Becherini, Yvonne
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Punch, Michael
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Paris Diderot University, France.
    Ernenwein, Jean-Pierre
    Aix-Marseille University, France.
    Very-High-Energy gamma-ray astronomy with the ALTO observatory2018In: 35th International Cosmic Ray Conference;ICRC2017, Busan, Korea, July 10-20, 2017, Trieste: Sissa Medialab , 2018, article id 782Conference paper (Refereed)
    Abstract [en]

    ALTO is a concept/project in the exploratory phase since 2013 aiming to build a wide-field Very-High-Energy gamma-ray observatory at very high altitude in the Southern hemisphere. The operation of such an observatory will complement the Northern hemisphere observations performed by HAWC and will make possible the exploration of the central region of our Galaxy and the hunt for PeVatrons, and to search for extended Galactic objects such as the Vela Supernova Remnant and the Fermi bubbles. 

    The ALTO project is aiming for a substantial improvement of the Water Cherenkov Detection Technique by increasing the altitude of the observatory in order to lower the energy threshold, by using a layer of scintillator below the water tank to optimize the signal over background discrimination, by minimizing the size of the tanks and having a more compact array to sample the air-shower footprints with better precision, and by using precise electronics which will provide time-stamped waveforms to improve the angular and energy resolution. ALTO is designed to have as low an energy threshold as possible so as to act as a fast trigger alert to other observatories -- primarily to the Southern part of CTA -- for transient Galactic and extra-galactic phenomena. 

    The wide field-of-view resulting from the detection technique allows the survey of a large portion of the sky continuously, thus giving the possibility to access emission from Gamma-Ray Bursts, Active Galactic Nuclei and X-ray binary flares, and extended emissions of both Galactic (Vela SNR, Fermi bubbles) and extra-galactic (AGN radio lobes) origin. The ALTO observatory will be composed of about a thousand detection units, each of which consists of a Water Cherenkov Detector positioned above a liquid Scintillation Detector, distributed within an area of about 200 m in diameter. The project is in the design study phase which is soon to be followed by a prototyping phase. The ALTO concept, design study and expected sensitivity together with the prototype status and plans for final deployment in the Southern hemisphere will be the subjects of this presentation.

  • 185. Bernloehr, K.
    et al.
    Barnacka, A.
    Becherini, Yvonne
    Ecole Polytechnique.
    Blanch Bigas, O.
    Carmona, E.
    Colin, P.
    Decerprit, G.
    Di Pierro, F.
    Dubois, F.
    Farnier, C.
    Funk, S.
    Hermann, G.
    Hinton, J. A.
    Humensky, T. B.
    Khelifi, B.
    Kihm, T.
    Komin, N.
    Lenain, J-P
    Maier, G.
    Mazin, D.
    Medina, M. C.
    Moralejo, A.
    Nolan, S. J.
    Ohm, S.
    Wilhelmi, E. de Ona
    Parsons, R. D.
    Arribas, M. Paz
    Pedaletti, G.
    Pita, S.
    Prokoph, Heike
    Rulten, C. B.
    Schwanke, U.
    Shayduk, M.
    Stamatescu, V.
    Vallania, P.
    Vorobiov, S.
    Wischnewski, R.
    Yoshikoshi, T.
    Zech, A.
    Monte Carlo design studies for the Cherenkov Telescope Array2013In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 43, p. 171-188Article in journal (Refereed)
    Abstract [en]

    The Cherenkov Telescopes Array (CTA) is planned as the future instrument for very-high-energy (VHE) gamma-ray astronomy with a wide energy range of four orders of magnitude and an improvement in sensitivity compared to current instruments of about an order of magnitude. Monte Carlo simulations are a crucial tool in the design of CTA. The ultimate goal of these simulations is to find the most cost-effective solution for given physics goals and thus sensitivity goals or to find, for a given cost, the solution best suited for different types of targets with CTA. Apart from uncertain component cost estimates, the main problem in this procedure is the dependence on a huge number of configuration parameters, both in specifications of individual telescope types and in the array layout. This is addressed by simulation of a huge array intended as a superset of many different realistic array layouts, and also by simulation of array subsets for different telescope parameters. Different analysis methods - in use with current installations and extended (or developed specifically) for CTA - are applied to the simulated data sets for deriving the expected sensitivity of CTA. In this paper we describe the current status of this iterative approach to optimize the CTA design and layout. (C) 2012 Elsevier B.V. All rights reserved.

  • 186. Biteau, J.
    et al.
    Becherini, Yvonne
    Ecole Polytech.
    Sanchez, D. A.
    Perkins, J. S.
    H.E.S.S Collaboration,
    The detection at high and very high energies of the blazar 1ES 1312-4232012In: HIGH ENERGY GAMMA-RAY ASTRONOMY, American Institute of Physics (AIP), 2012, p. 506-509Conference paper (Refereed)
    Abstract [en]

    The deep observation campaign led on Centaurus A with the High Energy Stereoscopic System (H. E. S. S.) has revealed a significant very high energy (VHE, E >= 100 GeV) excess coincident with the blazar 1ES 1312-423, 2 degrees away from the radio galaxy. The source is also detected at high energy (HE, 20 MeV - 300 GeV) with the Fermi Large Area Telescope (Fermi-LAT) after 3.5 years of all-sky monitoring. The high and very high energy spectra, together with Swift-XRT and ATOM observations are used to draw the first broad band spectral energy distribution (SED) of 1ES 1312-423. The non-thermal emission of this faint HBL is reproduced with a synchrotron self-Compton (SSC) model combined with a black-body spectrum for the host galaxy.

  • 187.
    Bolmont, J.
    et al.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Corona, P.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Gauron, P.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Ghislain, P.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Goffin, C.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Riveros, L. Guevara
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Huppert, J. -F
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Martineau-Huynh, O.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Nayman, P.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Parraud, J. -M
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Tavernet, J. -P
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Toussenel, F.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Vincent, D.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Vincent, P.
    Pierre-and-Marie-Curie University, France ; Paris Diderot University, France.
    Bertoli, W.
    Paris Diderot University, France.
    Espigat, P.
    Paris Diderot University, France.
    Punch, Michael
    Univ Paris Diderot, APC, AstroParticule & Cosmology, CNRS,IN2P3,CEA,Irfu, Observ Paris,Sorbonne Paris C, 10 Rue Alice Domon & Leonie Duquet, F-75205 Paris 13, France.
    Besin, D.
    Delagnes, E.
    CEA Saclay, France.
    Glicenstein, J. -F
    CEA Saclay, France.
    Moudden, Y.
    CEA Saclay, France.
    Venault, P.
    CEA Saclay, France.
    Zaghia, H.
    CEA Saclay, France.
    Brunetti, L.
    University of Savoy, France.
    David, P. -Y
    University of Savoy, France.
    Dubois, J. -M
    University of Savoy, France.
    Fiasson, A.
    University of Savoy, France.
    Geffroy, N.
    University of Savoy, France.
    Monteiro, I. Gomes
    University of Savoy, France.
    Journet, L.
    University of Savoy, France.
    Krayzel, F.
    University of Savoy, France.
    Lamanna, G.
    University of Savoy, France.
    Le Flour, T.
    University of Savoy, France.
    Lees, S.
    University of Savoy, France.
    Lieunard, B.
    University of Savoy, France.
    Maurin, G.
    University of Savoy, France.
    Mugnier, P.
    University of Savoy, France.
    Panazol, J-L
    University of Savoy, France.
    Prast, J.
    University of Savoy, France.
    Chounet, L. -M
    Ecole Polytechnique, France.
    Degrange, B.
    Ecole Polytechnique, France.
    Edy, E.
    Ecole Polytechnique, France.
    Fontaine, G.
    Ecole Polytechnique, France.
    Giebels, B.
    Ecole Polytechnique, France.
    Hormigos, S.
    Ecole Polytechnique, France.
    Khelifi, B.
    Ecole Polytechnique, France.
    Manigot, P.
    Ecole Polytechnique, France.
    Maritaz, P.
    Ecole Polytechnique, France.
    de Naurois, M.
    Ecole Polytechnique, France.
    Compin, M.
    Montpellier 2 University, France.
    Feinstein, F.
    Montpellier 2 University, France.
    Fernandez, D.
    Montpellier 2 University, France.
    Mehault, J.
    Montpellier 2 University, France.
    Rivoire, S.
    Montpellier 2 University, France.
    Royer, S.
    Montpellier 2 University, France.
    Sanguillon, M.
    Montpellier 2 University, France.
    Vasileiadis, G.
    Montpellier 2 University, France.
    The camera of the fifth H.E.S.S. telescope: Part I: System description2014In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 761, p. 46-57Article in journal (Refereed)
    Abstract [en]

    In July 2012, as the four ground based gamma-ray telescopes of the H.E.S.S. (High Energy Stereoscopic System) array reached their tenth year of operation in Khomas Highlands, Namibia, a fifth telescope Look its first data as part of the system. This new Cherenkov detector, comprising a 614.5 m(2) reflector with a highly pixelized camera in its focal plane, improves the sensitivity of the current array by a factor two and extends ifs energy domain down to a few Lens of GeV. The present part l of the paper gives a detailed description of the fifth H.E.S.S. telescope's camera, presenting the details of both the hardware and the software, emphasizing the main improvements as compared to previous H.E.S.S. camera technology.

  • 188.
    Bonardi, A.
    et al.
    Radboud University Nijmegen, Netherlands.
    Buanes, T.
    University of Bergen, Norway.
    Chadwick, P.
    Durham University, UK.
    Dazzi, F.
    Max Planck Institute, Germany.
    Förster, A.
    Max Planck Institute, Germany.
    Hörandel, J. R.
    Radboud University Nijmegen, Netherlands.
    Punch, Michael
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Wagner, R. M.
    Stockholm University.
    CTA Consortium,
    Central acceptance testing for camera technologies for the cherenkov telescope array2015In: Proceedings of Science, 2015Conference paper (Refereed)
    Abstract [en]

    The Cherenkov Telescope Array (CTA) is an international initiative to build the next generation ground based very-high energy gamma-ray observatory. It will consist of telescopes of three different sizes, employing several different technologies for the cameras that detect the Cherenkov light from the observed air showers. In order to ensure the compliance of each camera technology with CTA requirements, CTA will perform central acceptance testing of each camera technology. To assist with this, the Camera Test Facilities (CTF) work package is developing a detailed test program covering the most important performance, stability, and durability requirements, including setting up the necessary equipment. Performance testing will include a wide range of tests like signal amplitude, time resolution, dead-time determination, trigger efficiency, performance testing under temperature and humidity variations and several others. These tests can be performed on fully-integrated cameras using a portable setup at the camera construction sites. In addition, two different setups for performance tests on camera sub-units are being built, which can provide early feedback for camera development. Stability and durability tests will include the long-term functionality of movable parts, water tightness of the camera housing, temperature and humidity cycling, resistance to vibrations during transport or due to possible earthquakes, UV-resistance of materials and several others. Some durability tests will need to be contracted out because they will need dedicated equipment not currently available within CTA. The planned test procedures and the current status of the test facilities will be presented.

  • 189.
    Bonardi, A.
    et al.
    Radboud University, The Netherlands.
    Buitink, S.
    Vrije Universiteit Brussel, Belgium.
    Corstanje, A.
    Radboud University, The Netherlands.
    Falcke, H.
    Radboud University, The Netherlands;NIKHEF, Science Park Amsterdam, The Netherlands;Netherlands Institute of Radio Astronomy (ASTRON),The Netherlands.
    Hare, B. M.
    University Groningen, The Netherlands.
    Hörandel, J. R.
    Radboud University, The Netherlands;NIKHEF, Science Park Amsterdam, The Netherlands.
    Mitra, P.
    Vrije Universiteit Brussel, Belgium.
    Mulrey, K.
    Vrije Universiteit Brussel, Belgium.
    Nelles, A.
    Radboud University, The Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, The Netherlands.
    Rossetto, L.
    Radboud University,The Netherlands.
    Schellart, P.
    Radboud University, The Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, The Netherlands;Vrije Universiteit Brussel, Belgium.
    Ter Veen, S.
    Radboud University, The Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), The Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, The Netherlands.
    Trinh, T. N. G.
    University Groningen, The Netherlands.
    Winchen, T.
    Vrije Universiteit Brussel, Belgium.
    Study of the LOFAR radio self-trigger and single-station acquisition mode2018In: 35th International Cosmic Ray Conference, ICRC 2017, 10-20 July 2017, Sissa Medialab Srl , 2018, article id 402Conference paper (Refereed)
    Abstract [en]

    The LOw Frequency ARay (LOFAR) observatory is a multipurpose radio antenna array aimed to detect radio signals in the frequency range 10-240 MHz. Radio antennas are clustered into over 50 stations, and are spread along Central and Northern Europe. The LOFAR core, where the density of stations is highest, is instrumented with the LOfar Radboud air shower Array (LORA), covering an area of about 300 m diameter centered at the LOFAR core position. Since 2011 the LOFAR core has been used for detecting radio-signals associated to cosmic-ray air showers in the energy range 1016 - 1018 eV. Data acquisition is triggered by the LORA scintillator array, which provides energy, arrival direction, and core position estimates of the detected air shower too. Thus only the core of the LOFAR array is currently used for cosmic-ray detection. In order to extend the energy range of the detected cosmic rays, it is necessary to expand the effective collecting area to the whole LOFAR array. On this purpose, a detailed study about the LOFAR potentialities of working in self-trigger mode, i.e. with the cosmic-ray data acquisition trigger provided by the radio-antenna only, is presented here. A new method based on the intensity and the frequency spectrum for determining the air shower position to be implemented on LOFAR remote stations is presented too. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).

  • 190.
    Buitink, S.
    et al.
    Vrije Universiteit Brussel, Belgium.
    Bonardi, A.
    Radboud University, The Netherlands.
    Corstanje, A.
    Radboud University, The Netherlands.
    Falcke, H.
    Radboud University, The Netherlands;NIKHEF, Science Park Amsterdam, The Netherlands;Netherlands Institute of Radio Astronomy (ASTRON),Thr Netherlands.
    Hare, B. M.
    University Groningen, The Netherlands.
    Hörandel, J. R.
    Vrije Universiteit Brussel, Belgium;NIKHEF, Science Park Amsterdam, The Netherlands.
    Mitra, P.
    Vrije Universiteit Brussel, Belgium.
    Mulrey, K.
    Vrije Universiteit Brussel, Belgium.
    Nelles, A.
    Radboud University, The Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, The Netherlands.
    Rossetto, L.
    Radboud University,The Netherlands.
    Schellart, P.
    Radboud University, The Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, The Netherlands;Vrije Universiteit Brussel,Belgium.
    Ter Veen, S.
    Radboud University, The Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), The Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, The Netherlands.
    Trinh, T. N. G.
    University Groningen, The Netherlands.
    Winchen, T.
    Vrije Universiteit Brussel, Belgium.
    Cosmic ray mass composition with LOFAR2018In: 35th International Cosmic Ray Conference — ICRC2017. 10–20 July, 2017. Bexco, Busan, Korea, Sissa Medialab Srl , 2018, article id 499Conference paper (Refereed)
    Abstract [en]

    The LOFAR radio telescope measures the radio emission from extensive air showers with unprecedented precision. In the dense core individual air showers are detected by hundreds of dipole antennas. By fitting the complex radiation pattern to Monte Carlo radio simulation codes we obtain measurements of the atmospheric depth of the shower maximum X max with a precision of &lt; 20 g/cm 2 . This quantity is sensitive to the mass composition of cosmic rays. We discuss the first mass composition results of LOFAR and the improvements that are currently being made to enhance the accuracy of future analysis. Firstly, a more realistic treatment of the atmosphere will decrease the systematic uncertainties due to the atmosphere. Secondly, a series of upgrades to the LOFAR system will lead to increased effective area, duty cycle, and the possibility to extend the composition analysis down to the energy of 10 16.5 eV. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).

  • 191.
    Buitink, S.
    et al.
    Radboud University Nijmegen, The Netherlands.
    Corstanje, A.
    Radboud University Nijmegen, The Netherlands.
    Enriquez, J. E.
    Radboud University Nijmegen, The Netherlands.
    Falcke, H.
    Radboud University Nijmegen, The Netherlands ; Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands ; Science Park Amsterdam, The Netherlands ; Max Planck Institute for Radio Astronomy, Germany.
    Hörandel, J. R.
    Radboud University Nijmegen, The Netherlands ; Science Park Amsterdam, The Netherlands.
    Huege, T.
    Karlsruhe Institute of Technology (KIT), Germany.
    Nelles, A.
    Radboud University Nijmegen, The Netherlands.
    Rachen, J. P.
    Radboud University Nijmegen, The Netherlands.
    Schellart, P.
    Radboud University Nijmegen, The Netherlands.
    Scholten, O.
    University of Groningen, The Netherlands.
    ter Veen, S.
    Radboud University Nijmegen, The Netherlands.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Trinh, T. N. G.
    University of Groningen, The Netherlands.
    Method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles2014In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 90, no 8, p. 1-12, article id 082003Article in journal (Refereed)
    Abstract [en]

    The mass composition of cosmic rays contains important clues about their origin. Accurate measurements are needed to resolve longstanding issues such as the transition from Galactic to extra-Galactic origin and the nature of the cutoff observed at the highest energies. Composition can be studied by measuring the atmospheric depth of the shower maximum Xmax of air showers generated by high-energy cosmic rays hitting the Earth’s atmosphere. We present a new method to reconstruct Xmax based on radio measurements. The radio emission mechanism of air showers is a complex process that creates an asymmetric intensity pattern on the ground. The shape of this pattern strongly depends on the longitudinal development of the shower. We reconstruct Xmax by fitting two-dimensional intensity profiles, simulated with CoREAS, to data from the Low Frequency Array (LOFAR) radio telescope. In the dense LOFAR core, air showers are detected by hundreds of antennas simultaneously. The simulations fit the data very well, indicating that the radiation mechanism is now well understood. The typical uncertainty on the reconstruction of Xmax for LOFAR showers is 17  g/cm2.

  • 192.
    Buitink, S.
    et al.
    Vrije Universiteit Brussel, Belgium ; Radboud University Nijmegen, The Netherlands.
    Corstanje, A.
    Radboud University Nijmegen, The Netherlands.
    Falcke, H.
    Radboud University Nijmegen, The Netherlands ; ASTRON, The Netherlands ; Science Park Amsterdam, The Netherlands ; Max-Planck-Institut für Radioastronomie, Germany.
    Hörandel, J. R.
    Radboud University Nijmegen, The Netherlands ; Science Park Amsterdam, The Netherlands.
    Huege, T.
    Karlsruhe Institute of Technology (KIT), Germany.
    Nelles, A.
    University of California Irvine, USA.
    Rachen, J. P.
    Radboud University Nijmegen, The Netherlands.
    Rossetto, L.
    Radboud University Nijmegen, The Netherlands.
    Schellart, P.
    Radboud University Nijmegen, The Netherlands.
    Scholten, O.
    University of Groningen, The Netherlands ; Vrije Universiteit Brussel, Belgium.
    Ter Veen, S.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Trinh, T. N. G.
    Anderson, J.
    Asgekar, A.
    Avruch, I. M.
    Bell, M. E.
    Bentum, M. J.
    Bernardi, G.
    Best, P.
    Bonafede, A.
    Breitling, F.
    Broderick, J. W.
    Brouw, W. N.
    Brüggen, M.
    Butcher, H. R.
    Carbone, D.
    Ciardi, B.
    Conway, J. E.
    de Gasperin, F.
    de Geus, E.
    Deller, A.
    Dettmar, R. -J
    van Diepen, G.
    Duscha, S.
    Eislöffel, J.
    Engels, D.
    Enriquez, J. E.
    Fallows, R. A.
    Fender, R.
    Ferrari, C.
    Frieswijk, W.
    Garrett, M. A.
    Grießmeier, J. M.
    Gunst, A. W.
    van Haarlem, M. P.
    Hassall, T. E.
    Heald, G.
    Hessels, J. W. T.
    Hoeft, M.
    Horneffer, A.
    Iacobelli, M.
    Intema, H.
    Juette, E.
    Karastergiou, A.
    Kondratiev, V. I.
    Kramer, M.
    Kuniyoshi, M.
    Kuper, G.
    van Leeuwen, J.
    Loose, G. M.
    Maat, P.
    Mann, G.
    Markoff, S.
    McFadden, R.
    McKay-Bukowski, D.
    McKean, J. P.
    Mevius, M.
    Mulcahy, D. D.
    Munk, H.
    Norden, M. J.
    Orru, E.
    Paas, H.
    Pandey-Pommier, M.
    Pandey, V. N.
    Pietka, M.
    Pizzo, R.
    Polatidis, A. G.
    Reich, W.
    Röttgering, H. J. A.
    Scaife, A. M. M.
    Schwarz, D. J.
    Serylak, M.
    Sluman, J.
    Smirnov, O.
    Stappers, B. W.
    Steinmetz, M.
    Stewart, A.
    Swinbank, J.
    Tagger, M.
    Tang, Y.
    Tasse, C.
    Toribio, M. C.
    Vermeulen, R.
    Vocks, C.
    Vogt, C.
    van Weeren, R. J.
    Wijers, R. A. M. J.
    Wijnholds, S. J.
    Wise, M. W.
    Wucknitz, O.
    Yatawatta, S.
    Zarka, P.
    Zensus, J. A.
    A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 531, no 7592, p. 70-73Article in journal (Refereed)
    Abstract [en]

    Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017–1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal1 comes from accelerators capable of producing cosmic rays of these energies2. Cosmic rays initiate air showers—cascades of secondary particles in the atmosphere—and their masses can be inferred from measurements of the atmospheric depth of the shower maximum3 (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground4. Current measurements5 have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays6, 7, 8 is a rapidly developing technique9 for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front6, 12. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017–1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017–1017.5 electronvolt range.

  • 193.
    Buitink, Stijn
    et al.
    University of Groningen, The Netherlands ; Radboud University Nijmegen, The Netherlands.
    Corstanje, Arthur
    Radboud University Nijmegen, The Netherlands.
    Enriquez, Emilio
    Radboud University Nijmegen, The Netherlands.
    Falcke, Heino
    Radboud University Nijmegen, The Netherlands ; Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Frieswijk, Wilfred
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Hörandel, Jörg
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Mevius, Maaijke
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Nelles, Anna
    Radboud University Nijmegen, The Netherlands ; Science Park Amsterdam, The Netherlands.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Schellart, Pim
    Radboud University Nijmegen, The Netherlands.
    Scholten, Olaf
    University of Groningen, The Netherlands.
    ter Veen, Sander
    Radboud University Nijmegen, The Netherlands.
    van den Akker, Martin
    Radboud University Nijmegen, The Netherlands.
    Searching for neutrino radio flashes from the Moon with LOFAR2013In: 5th International Workshop on Acoustic and Radio EeV Neutrino Detection Activities: Arena 2012 / [ed] Robert Lahmann, Thomas Eberl, Kay Graf, Clancy James, Tim Huege, Timo Karg, Rolf Nahnhauer, American Institute of Physics (AIP), 2013, Vol. 1535, p. 27-31Conference paper (Refereed)
    Abstract [en]

    Ultra-high-energy neutrinos and cosmic rays produce short radio flashes through the Askaryan effect when they impact on the Moon. Earthbound radio telescopes can search the Lunar surface for these signals. A new generation of lowfrequency, digital radio arrays, spearheaded by LOFAR, will allow for searches with unprecedented sensitivity. In the first stage of the NuMoon project, low-frequency observations were carried out with the Westerbork Synthesis Radio Telescope, leading to the most stringent limit on the cosmic neutrino flux above 1023 eV. With LOFAR we will be able to reach a sensitivity of over an order of magnitude better and to decrease the threshold energy.

  • 194.
    Cerruti, M.
    et al.
    Univ Paris Diderot, France.
    Bottcher, M.
    North West Univ, South Africa.
    Chakraborty, N.
    Max Planck Inst Kernphys, Germany.
    Davids, I. D.
    North West Univ, South Africa ; Univ Namibia, Namibia.
    Fuessling, M.
    DESY, Germany.
    Jankowsky, F.
    Heidelberg Univ, Germany.
    Lenain, J. P.
    Univ Paris Diderot, France.
    Meyer, M.
    Stockholm University.
    Prokoph, Heike
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Wagner, S.
    Heidelberg Univ, Germany.
    Zaborov, D.
    Ecole Polytech, France.
    Zacharias, M.
    Heidelberg Univ, Germany.
    Target of Opportunity Observations of Blazars with HESS2017In: HIGH ENERGY GAMMA-RAY ASTRONOMY / [ed] Aharonian, FA Hofmann, W Rieger, FM, American Institute of Physics (AIP), 2017, article id UNSP 050029Conference paper (Refereed)
    Abstract [en]

    The very high energy (VHE, E > 100 GeV) sky is dominated by blazars, radio-loud active galactic nuclei whose relativistic jet is closely aligned with the line of sight. Blazars are characterized by rapid variability at all wavelengths and thus an important part of the H.E.S.S. blazar program is devoted to target of opportunity (ToO) observations. H.E.S.S. triggers blazar ToOs on the basis of publicly available blazar observations at longer wavelengths (optical, X-rays, and gamma-rays), from private optical observations with the ATOM telescope, and from private communications by gamma-ray partners in the context of MoUs. In 2015, about 70 hours of H.E.S.S. data were taken in the form of blazar ToOs, which represents 15% of all extragalactic observations. In this contribution, we present the H.E.S.S. blazar ToO status, and we focus on two major results from the 2015 season: the detection of VHE emission from 3C 279 during the June 2015 flare, and the discovery of PKS 0736+017 as a new VHE quasar.

  • 195. Coenen, T.
    et al.
    van Leeuwen, J.
    Hessels, J. W. T.
    Stappers, B. W.
    Kondratiev, V. I.
    Alexov, A.
    Breton, R. P.
    Bilous, A.
    Cooper, S.
    Falcke, H.
    Fallows, R. A.
    Gajjar, V.
    Grießmeier, J. -M
    Hassall, T. E.
    Karastergiou, A.
    Keane, E. F.
    Kramer, M.
    Kuniyoshi, M.
    Noutsos, A.
    Os\lowski, S.
    Pilia, M.
    Serylak, M.
    Schrijvers, C.
    Sobey, C.
    ter Veen, S.
    Verbiest, J.
    Weltevrede, P.
    Wijnholds, S.
    Zagkouris, K.
    van Amesfoort, A. S.
    Anderson, J.
    Asgekar, A.
    Avruch, I. M.
    Bell, M. E.
    Bentum, M. J.
    Bernardi, G.
    Best, P.
    Bonafede, A.
    Breitling, F.
    Broderick, J.
    Brüggen, M.
    Butcher, H. R.
    Ciardi, B.
    Corstanje, A.
    Deller, A.
    Duscha, S.
    Eislöffel, J.
    Fender, R.
    Ferrari, C.
    Frieswijk, W.
    Garrett, M. A.
    de Gasperin, F.
    de Geus, E.
    Gunst, A. W.
    Hamaker, J. P.
    Heald, G.
    Hoeft, M.
    van der Horst, A.
    Juette, E.
    Kuper, G.
    Law, C.
    Mann, G.
    McFadden, R.
    McKay-Bukowski, D.
    McKean, J. P.
    Munk, H.
    Orru, E.
    Paas, H.
    Pandey-Pommier, M.
    Polatidis, A. G.
    Reich, W.
    Renting, A.
    Röttgering, H.
    Rowlinson, A.
    Scaife, A. M. M.
    Schwarz, D.
    Sluman, J.
    Smirnov, O.
    Swinbank, J.
    Tagger, M.
    Tang, Y.
    Tasse, C.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Toribio, C.
    Vermeulen, R.
    Vocks, C.
    van Weeren, R. J.
    Wucknitz, O.
    Zarka, P.
    Zensus, A.
    The LOFAR pilot surveys for pulsars and fast radio transients2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 570, p. 1-16, article id A60Article in journal (Refereed)
    Abstract [en]

    We have conducted two pilot surveys for radio pulsars and fast transients with the Low-Frequency Array (LOFAR) around 140 MHz and here report on the first low-frequency fast-radio burst limit and the discovery of two new pulsars. The first survey, the LOFAR Pilot Pulsar Survey (LPPS), observed a large fraction of the northern sky, ~ 1.4 × 104 deg2, with 1 h dwell times. Each observation covered ~75 deg2 using 7 independent fields formed by incoherently summing the high-band antenna fields. The second pilot survey, the LOFAR Tied-Array Survey (LOTAS), spanned ~600 deg2, with roughly a 5-fold increase in sensitivity compared with LPPS. Using a coherent sum of the 6 LOFAR “Superterp” stations, we formed 19 tied-array beams, together covering 4 deg2 per pointing. From LPPS we derive a limit on the occurrence, at 142 MHz, of dispersed radio bursts of < 150 day-1 sky-1, for bursts brighter than S> 107  Jy for the narrowest searched burst duration of 0.66 ms. In LPPS, we re-detected 65 previously known pulsars. LOTAS discovered two pulsars, the first with LOFAR or any digital aperture array. LOTAS also re-detected 27 previously known pulsars. These pilot studies show that LOFAR can efficiently carry out all-sky surveys for pulsars and fast transients, and they set the stage for further surveying efforts using LOFAR and the planned low-frequency component of the Square Kilometer Array.

  • 196.
    Colafrancesco, Sergio
    et al.
    ASI Science Data Center, ASDC c/o ESRIN, Italy ; ASI, Italy ; INAF – Osservatorio Astronomico di Roma, Italy.
    Prokhorov, Dmitry
    Moscow Institute of Physics and Technology, Russia ; Université Pierre et Marie Curie, France.
    Dogiel, Vladimir
    Lebedev Physical Institute, Russia.
    Studying the leptonic structure of galaxy cluster atmospheres from the spectral properties of the SZ effect2009In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 494, no 1, p. 1-9Article in journal (Refereed)
    Abstract [en]

    We study the energetics of galaxy-cluster atmospheres by analyzing the SZ effect spectra around the crossover frequency. We calculate analytically the expressions of both the crossover frequency and the spectral slope of the SZE around the crossover frequency in various cases: a thermal electron population; a power-law, non-thermal, electron population; and a population of electrons experiencing a stochastic acceleration. We find that the value of the crossover frequency X0 of the SZE depends significantly on the cluster peculiar velocity Vr which determines the amplitude of the kinematic SZE), while the value of the slope of the SZE does not depend on the kinematic SZE spectrum in the optimal frequency range around the crossover frequency of the thermal SZE, i.e. in the frequency range x = 3.5 - 4.5. Therefore, while the amplitude of the SZ   produces a systematic bias in the position of the crossover frequency X0, it does not affect significantly the spectral slope of the SZE. We therefore propose using measurements of the spectral slope of the SZE to obtain unbiased information about the specific properties of various electron distributions in galaxy clusters as well as in other cosmic structures in which a SZE can be produced.

  • 197. Collaboration, H. E. S. S.
    et al.
    Abramowski, A.
    Aharonian, F.
    Benkhali, F. Ait
    Akhperjanian, A. G.
    Anguener, E.
    Anton, G.
    Balenderan, S.
    Balzer, A.
    Barnacka, A.
    Becherini, Yvonne
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Tjus, J. Becker
    Bernloehr, K.
    Birsin, E.
    Bissaldi, E.
    Biteau, J.
    Boettcher, M.
    Boisson, C.
    Bolmont, J.
    Bordas, P.
    Brucker, J.
    Brun, F.
    Brun, P.
    Bulik, T.
    Carrigan, S.
    Casanova, S.
    Cerruti, M.
    Chadwick, P. M.
    Chalme-Calvet, R.
    Chaves, R. C. G.
    Cheesebrough, A.
    Chretien, M.
    Colafrancesco, S.
    Cologna, G.
    Conrad, J.
    Couturier, C.
    Cui, Y.
    Dalton, M.
    Daniel, M. K.
    Davids, I. D.
    Degrange, B.
    Deil, C.
    de Wilt, P.
    Dickinson, H. J.
    Djannati-Atai, A.
    Domainko, W.
    Drury, L. O 'C.
    Dubus, G.
    Dutson, K.
    Dyks, J.
    Dyrda, M.
    Edwards, T.
    Egberts, K.
    Eger, P.
    Espigat, P.
    Farnier, C.
    Fegan, S.
    Feinstein, F.
    Fernandes, M. V.
    Fernandez, D.
    Fiasson, A.
    Fontaine, G.
    Foerster, A.
    Fuessling, M.
    Gajdus, M.
    Gallant, Y. A.
    Garrigoux, T.
    Giavitto, G.
    Giebels, B.
    Glicenstein, J. F.
    Grondin, M. -H
    Grudzinska, M.
    Haeffner, S.
    Hahn, J.
    Harris, J.
    Heinzelmann, G.
    Henri, G.
    Hermann, G.
    Hervet, O.
    Hillert, A.
    Hinton, J. A.
    Hofmann, W.
    Hofverberg, P.
    Holler, M.
    Horns, D.
    Jacholkowska, A.
    Jahn, C.
    Jamrozy, M.
    Janiak, M.
    Jankowsky, F.
    Jung, I.
    Kastendieck, M. A.
    Katarzynski, K.
    Katz, U.
    Kaufmann, S.
    Khelifi, B.
    Kieffer, M.
    Klepser, S.
    Klochkov, D.
    Kluzniak, W.
    Kneiske, T.
    Kolitzus, D.
    Komin, Nu.
    Kosack, K.
    Krakau, S.
    Krayzel, F.
    Krueger, P. P.
    Laffon, H.
    Lamanna, G.
    Lefaucheur, J.
    Lemiere, A.
    Lemoine-Goumard, M.
    Lenain, J. -P
    Lennarz, D.
    Lohse, T.
    Lopatin, A.
    Lu, C. -C
    Marandon, V.
    Marcowith, A.
    Marx, R.
    Maurin, G.
    Maxted, N.
    Mayer, M.
    McComb, T. J. L.
    Mehault, J.
    Meintjes, P. J.
    Menzler, U.
    Meyer, M.
    Moderski, R.
    Mohamed, M.
    Moulin, E.
    Murach, T.
    Naumann, C. L.
    de Naurois, M.
    Niemiec, J.
    Nolan, S. J.
    Oakes, L.
    Ohm, S.
    Wilhelmi, E. de Ona
    Opitz, B.
    Ostrowski, M.
    Oya, I.
    Panter, M.
    Parsons, R. D.
    Arribas, M. Paz
    Pekeur, N. W.
    Pelletier, G.
    Perez, J.
    Petrucci, P. -O
    Peyaud, B.
    Pita, S.
    Poon, H.
    Puehlhofer, G.
    Punch, Michael
    Univ Paris Diderot, APC, AstroParticule & Cosmology, CNRS,IN2P3,CEA,Irfu, Observ Paris,Sorbonne Paris C, 10 Rue Alice Domon & Leonie Duquet, F-75205 Paris 13, France.
    Quirrenbach, A.
    Raab, S.
    Raue, M.
    Reimer, A.
    Reimer, O.
    Renaud, M.
    de los Reyes, R.
    Rieger, F.
    Rob, L.
    Romoli, C.
    Rosier-Lees, S.
    Rowell, G.
    Rudak, B.
    Rulten, C. B.
    Sahakian, V.
    Sanchez, D. A.
    Santangelo, A.
    Schlickeiser, R.
    Schuessler, F.
    Schulz, A.
    Schwanke, U.
    Schwarzburg, S.
    Schwemmer, S.
    Sol, H.
    Spengler, G.
    Spies, F.
    Stawarz, L.
    Steenkamp, R.
    Stegmann, C.
    Stinzing, F.
    Stycz, K.
    Sushch, I.
    Szostek, A.
    Tavernet, J. -P
    Tavernier, T.
    Taylor, A. M.
    Terrier, R.
    Tluczykont, M.
    Trichard, C.
    Valerius, K.
    van Eldik, C.
    van Soelen, B.
    Vasileiadis, G.
    Venter, C.
    Viana, A.
    Vincent, P.
    Voelk, H. J.
    Volpe, F.
    Vorster, M.
    Vuillaume, T.
    Wagner, S. J.
    Wagner, P.
    Ward, M.
    Weidinger, M.
    Weitzel, Q.
    White, R.
    Wierzcholska, A.
    Willmann, P.
    Woernlein, A.
    Wouters, D.
    Zabalza, V.
    Zacharias, M.
    Zajczyk, A.
    Zdziarski, A. A.
    Zech, A.
    Zechlin, H. -S
    HESS observations of the Crab during its March 2013 GeV gamma-ray flare2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 562, p. Article ID: UNSP L4-Article in journal (Refereed)
    Abstract [en]

    Context. On March 4, 2013 the Fermi-EAT and AGILE reported a flare from the direction of the Crab nebula in which the high-energy (HE; E > 100 MeV) flux was six times above its quiescent level. Simultaneous observations in other energy bands give us hints about the emission processes during the flare episode and the physics of pulsar wind nebulae in general. Aims. We search for variability in the emission of the Crab nebula at very-high energies (VHF,; E > 100 GeV), using contemporaneous data taken with the H.E.S.S. array of Cherenkov telescopes. Methods. Observational data taken with the H.E.S.S. instrument on five consecutive days during the flare were analysed for the flux and spectral shape of the emission from the Crab nebula. Night-wise light curves are presented with energy thresholds of 1 TeV and 5 TeV. Results. The observations conducted with H.E.S.S. on March 6 to March 10, 2013 show no significant changes in the flux. They limit the variation in the integral flux above 1 TeV to less than 63% and the integral flux above 5 TeV to less than 78% at a 95% confidence level.

  • 198. Collaboration, V E R I T A S
    et al.
    Aliu, E.
    Arlen, T.
    Aune, T.
    Beilicke, M.
    Benbow, W.
    Bouvier, A.
    Bradbury, S. M.
    Buckley, J. H.
    Bugaev, V.
    Byrum, K.
    Cannon, A.
    Cesarini, A.
    Christiansen, J. L.
    Ciupik, L.
    Collins-Hughes, E.
    Connolly, M. P.
    Cui, W.
    Dickherber, R.
    Duke, C.
    Errando, M.
    Falcone, A.
    Finley, J. P.
    Finnegan, G.
    Fortson, L.
    Furniss, A.
    Galante, N.
    Gall, D.
    Gibbs, K.
    Gillanders, G. H.
    Godambe, S.
    Griffin, S.
    Grube, J.
    Guenette, R.
    Gyuk, G.
    Hanna, D.
    Holder, J.
    Huan, H.
    Hughes, G.
    Hui, C. M.
    Humensky, T. B.
    Imran, A.
    Kaaret, P.
    Karlsson, N.
    Kertzman, M.
    Kieda, D.
    Krawczynski, H.
    Krennrich, F.
    Lang, M. J.
    Lyutikov, M.
    Madhavan, A. S.
    Maier, G.
    Majumdar, P.
    McArthur, S.
    McCann, A.
    McCutcheon, M.
    Moriarty, P.
    Mukherjee, R.
    Nuñez, P.
    Ong, R. A.
    Orr, M.
    Otte, A. N.
    Park, N.
    Perkins, J. S.
    Pizlo, F.
    Pohl, M.
    Prokoph, Heike
    Deutsches Elektronen Synchrotron Germany.
    Quinn, J.
    Ragan, K.
    Reyes, L. C.
    Reynolds, P. T.
    Roache, E.
    Rose, H. J.
    Ruppel, J.
    Saxon, D. B.
    Schroedter, M.
    Sembroski, G. H.
    \c Sentürk, G. D.
    Smith, A. W.
    Staszak, D.
    Te\v sić, G.
    Theiling, M.
    Thibadeau, S.
    Tsurusaki, K.
    Tyler, J.
    Varlotta, A.
    Vassiliev, V. V.
    Vincent, S.
    Vivier, M.
    Wakely, S. P.
    Ward, J. E.
    Weekes, T. C.
    Weinstein, A.
    Weisgarber, T.
    Williams, D. A.
    Zitzer, B.
    Detection of Pulsed Gamma Rays Above 100 GeV from the Crab Pulsar2011In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 334, no 6052, p. 69-72Article in journal (Refereed)
    Abstract [en]

    We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 giga–electron volts (GeV) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon spectrum of pulsed emission between 100 mega–electron volts and 400 GeV is described by a broken power law that is statistically preferred over a power law with an exponential cutoff. It is unlikely that the observation can be explained by invoking curvature radiation as the origin of the observed gamma rays above 100 GeV. Our findings require that these gamma rays be produced more than 10 stellar radii from the neutron star.

  • 199.
    Corstanje, A.
    et al.
    Radboud University Nijmegen, The Netherlands.
    Buitink, S.
    Vrije Universiteit Brussel, Belgium.
    Enriquez, J. E.
    Radboud University Nijmegen, The Netherlands.
    Falcke, H.
    Radboud University Nijmegen, The Netherlands ; Science Park Amsterdam, The Netherlands ; Netherlands Institute for Radio Astronomy, The Netherlands ; Max Planck Institute for Radio Astronomy, Germany.
    Hörandel, J. R.
    Radboud University Nijmegen, The Netherlands ; Science Park Amsterdam, The Netherlands.
    Krause, M.
    Deutsches Elektronen-Synchrotron, Germany.
    Nelles, A.
    Radboud University Nijmegen, The Netherlands ; University of California Irvine, USA.
    Rachen, J. P.
    Radboud University Nijmegen, The Netherlands.
    Schellart, P.
    Radboud University Nijmegen, The Netherlands.
    Scholten, O.
    University Groningen, The Netherlands ; Vrije Universiteit Brussel, Belgium.
    ter Veen, S.
    Radboud University Nijmegen, The Netherlands.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Trinh, T. N. G.
    University Groningen, The Netherlands.
    Timing calibration and spectral cleaning of LOFAR time series data2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 590, article id A41Article in journal (Refereed)
    Abstract [en]

    We describe a method for spectral cleaning and timing calibration of short voltage time series data from individual radio interferometer receivers. It makes use of the phase differences in Fast Fourier Transform (FFT) spectra across antenna pairs. For strong, localized terrestrial sources these are stable over time, while being approximately uniform-random for a sum over many sources or for noise. Using only milliseconds-long datasets, the method finds the strongest interfering transmitters, a first-order solution for relative timing calibrations, and faulty data channels. No knowledge of gain response or quiescent noise levels of the receivers is required. With relatively small data volumes, this approach is suitable for use in an online system monitoring setup for interferometric arrays. We have applied the method to our cosmic-ray data collection, a collection of measurements of short pulses from extensive air showers, recorded by the LOFAR radio telescope. Per air shower, we have collected 2 ms of raw time series data for each receiver. The spectral cleaning has a calculated optimal sensitivity corresponding to a power signal-to-noise ratio of 0.08 (or -11 dB) in a spectral window of 25 kHz, for 2 ms of data in 48 antennas. This is well sufficient for our application. Timing calibration across individual antenna pairs has been performed at 0.4 ns precision; for calibration of signal clocks across stations of 48 antennas the precision is 0.1 ns. Monitoring differences in timing calibration per antenna pair over the course of the period 2011 to 2015 shows a precision of 0.08 ns, which is useful for monitoring and correcting drifts in signal path synchronizations. A cross-check method for timing calibration is presented, using a pulse transmitter carried by a drone flying over the array. Timing precision is similar, 0.3 ns.

  • 200.
    Corstanje, A.
    et al.
    Radboud University, The Netherlands.
    Mitra, P.
    Vrije Universiteit, Belgium.
    Bonardi, A.
    Radboud University, The Netherlands.
    Buitink, S.
    Vrije Universiteit, Belgium.
    Falcke, H.
    Radboud University, The Netherlands;NIKHEF, Science Park Amsterdam, The Netherlands;Netherlands Institute of Radio Astronomy (ASTRON),, The Netherlands.
    Hare, B. M.
    University Groningen, The Netherlands.
    Hörandel, J. R.
    Radboud University, The Netherlands;NIKHEF, Science Park Amsterdam, The Netherlands.
    Mulrey, K.
    Vrije Universiteit, Belgium.
    Nelles, A.
    Radboud University, The Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, The Netherlands.
    Rossetto, L.
    Radboud University,The Netherlands.
    Schellart, P.
    Radboud University, The Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, The Netherlands.
    Ter Veen, S.
    Radboud University, The Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), The Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, The Netherlands.
    Trinh, T. N. G.
    University Groningen, The Netherlands.
    Winchen, T.
    Vrije Universiteit, Belgium.
    The effect of the atmospheric refractive index on the radio signal of extensive air showers using Global Data Assimilation System (GDAS)2018In: 35th International Cosmic Ray Conference, ICRC 2017, 10-20 July 2017, Bexco, Busan, Korea, Sissa Medialab Srl , 2018Conference paper (Refereed)
    Abstract [en]

    One of the major systematic uncertainties in the measurement of Xmax from radio emission of EAS arises from variations of the refractive index in the atmosphere. The refractive index n varies with temperature, humidity and pressure, and the variations can be on the order of 10% for (n-1) at a given altitude. The effect of a varying refractive index on Xmax measurements is evaluated using CoREAS: a microscopic simulation of the radio emission from the individual particles in the cascade simulated with CORSIKA. We discuss the resulting offsets in Xmax for different frequency regimes, and compare them to a simple physical model. Under typical circumstances, the offsets in Xmax range from 4-11 g/cm2 for the 30-80 MHz frequency band. Therefore, for precise measurements it is required to include atmospheric data at the time and place of observation of the air shower into the simulations. The aim is to implement this in the next version of CoREAS/CORSIKA using the Global Data Assimilation System (GDAS), a global atmospheric model based on meteorological measurements and numerical weather predictions. This can then be used to re-evaluate the air shower measurements of the LOFAR radio telescope. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0).

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