lnu.sePublications
Change search
Refine search result
12 1 - 50 of 99
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Acero, F.
    et al.
    CEA Saclay, France.
    Aloisio, R.
    Arcetri Observatory, Italy ; University of L'Aquila, Italy ; Gran Sasso Science Institute, Italy.
    Amans, J.
    Paris Observatory, France.
    Amato, E.
    Arcetri Observatory, Italy.
    Antonelli, L. A.
    Rome Observatory, Italy.
    Aramo, C.
    INFN Sezione di Napoli, Italy.
    Armstrong, T.
    Durham University, UK.
    Arqueros, F.
    Complutense University of Madrid, Spain.
    Asano, K.
    University of Tokyo, Japan.
    Ashley, M.
    University of New South Wales, Australia.
    Backes, M.
    Univ Namibia, Namibia.
    Balazs, C.
    Monash Univ, Australia.
    Balzer, A.
    Univ Amsterdam, Netherlands.
    Bamba, A.
    Univ Tokyo, Japan.
    Barkov, M.
    RIKEN, Inst Phys & Chem Res, Hirosawa, Wako, Saitama 3510198, Japan..
    Barrio, J. A.
    Univ Complutense Madrid, Grp Altas Energias, Av Complutense, Madrid, Spain..
    Benbow, W.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02180 USA..
    Bernloehr, K.
    Max Planck Inst Kernphys, Saupfercheckweg 1, Heidelberg, Germany..
    Beshley, V.
    Inst Appl Problems Mech & Math, 3B Naukova St, Lvov, Ukraine..
    Bigongiari, C.
    Osserv Astron Torino, INAF, Corso Fiume 4, Turin, Italy..
    Biland, A.
    Swiss Fed Inst Technol, Inst Particle Phys, Schafmattstr 20, Zurich, Switzerland..
    Bilinsky, A.
    Ivan Franko Natl Univ Lviv, Astron Observ, 1 Univ Ska St, UA-79000 City Of Lviv, Ukraine..
    Bissaldi, E.
    Politecn Bari, Bari, Italy.;INFN Bari, Bari, Italy..
    Biteau, J.
    Univ Paris 11, IPNO, IN2P3, CNRS, 15 Rue Georges Clemenceau, Orsay, France.;Univ Paris 11, UMR 8608, 15 Rue Georges Clemenceau, Orsay, France..
    Blanch, O.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Blasi, P.
    Osserv Astrofis Arcetri, Largo E Fermi 5, Florence, Italy..
    Blazek, J.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Boisson, C.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Bonanno, G.
    INAF Osservatorio Astrofis Catania, Via S Sofia 78, Catania, Italy..
    Bonardi, A.
    Radboud Univ Nijmegen, POB 9010, GL Nijmegen, Netherlands..
    Bonavolonta, C.
    Ist Nazl Fis Nucl, Sez Napoli, Via Cintia,Ed G, Naples, Italy..
    Bonnoli, G.
    INAF Osservatorio Astron Brera, Via Brera 28, Milan, Italy..
    Braiding, C.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia..
    Brau-Nogue, S.
    IRAP, 9 Ave Colonel Roche,BP 44346, Toulouse 4, France..
    Bregeon, J.
    Univ Montpellier, CNRS, IN2P3, Lab Univers & Particules Montpellier, CC 72,Pl Eugene Bataillon, Montpellier 5, France..
    Brown, A. M.
    Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, UK;Univ Durham, Ctr Adv Instrumentat, South Rd, Durham DH1 3LE, UK.
    Bugaev, V.
    Washington Univ, Dept Phys, St Louis, MO 63130 USA..
    Bulgarelli, A.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    Bulik, T.
    Univ Warsaw, Fac Phys, Ul Hoza 69, Warsaw, Poland..
    Burton, M.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia..
    Burtovoi, A.
    INAF Osservatorio Astron Padova, Vicolo Osservatorio 5, Padua, Italy..
    Busetto, G.
    Univ Padua, Dipartimento Fis, Via Marzolo 8, Padua, Italy..
    Bottcher, M.
    North West Univ, Ctr Space Res, Potchefstroom Campus, Potchefstroom, South Africa..
    Cameron, R.
    Stanford Univ, Dept Phys, Kavli Inst Particle Astrophys & Cosmol, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA.;Stanford Univ, Dept Phys, SLAC Natl Accelerator Lab, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA..
    Capalbi, M.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    Caproni, A.
    UCS, NAT, Rua Galvao Bueno 8687,Bloco B,Sala 16, Sao Paulo, Brazil..
    Caraveo, P.
    Ist Astrofis Spaziale & Fis Cosm, Via Bassini 15, Milan, Italy..
    Carosi, R.
    Ist Nazl Fis Nucl, Sez Pisa, Largo Pontecorvo 3, Pisa, Italy..
    Cascone, E.
    INAF Osservatorio Astron Brera, Via Brera 28, Milan, Italy..
    Cerruti, M.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02180 USA..
    Chaty, S.
    CEA Saclay, CEA, IRFU, SAp, Bat 709, Gif Sur Yvette, France..
    Chen, A.
    Univ Witwatersrand, 1 Jan Smuts Ave, Johannesburg, South Africa..
    Chen, X.
    Pontificia Univ Catolica Chile, Avda Libertador Bernardo OHiggins 340, Santiago, Chile..
    Chernyakova, M.
    Dublin City Univ, Dublin 9, Ireland..
    Chikawa, M.
    Kindai Univ, Dept Phys, Higashiosaka, Osaka 5778502, Japan..
    Chudoba, J.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Cohen-Tanugi, J.
    Univ Montpellier, CNRS, IN2P3, Lab Univers & Particules Montpellier, CC 72,Pl Eugene Bataillon, Montpellier 5, France..
    Colafrancesco, S.
    Univ Witwatersrand, 1 Jan Smuts Ave, Johannesburg, South Africa..
    Conforti, V.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    Contreras, J. L.
    Univ Complutense Madrid, Grp Altas Energias, Av Complutense, Madrid, Spain..
    Costa, A.
    INAF Osservatorio Astrofis Catania, Via S Sofia 78, Catania, Italy..
    Cotter, G.
    Univ Oxford, Dept Phys, 1 Keble Rd, Oxford OX1 3NP, UK.
    Covino, S.
    INAF Osservatorio Astron Brera, Via Brera 28, Milan, Italy..
    Covone, G.
    Ist Nazl Fis Nucl, Sez Napoli, Via Cintia,Ed G, Naples, Italy..
    Cumani, P.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Cusumano, G.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    D'Ammando, F.
    INAF IRA, INAF, Ist Radioastron, Via Gobetti 101, Bologna, Italy..
    D'Urso, D.
    INFN, Sez Perugia, Via A Pascoli, Perugia, Italy..
    Daniel, M.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02180 USA..
    Dazzi, F.
    Cherenkov Telescope Array Observ, Saupfercheckweg 1, Heidelberg, Germany..
    De Angelis, A.
    Univ Padua, Dipartimento Fis, Via Marzolo 8, Padua, Italy..
    De Cesare, G.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    De Franco, A.
    Univ Oxford, Dept Phys, 1 Keble Rd, Oxford OX1 3NP, UK.
    De Frondat, F.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Dal Pino, E. M. de Gouveia
    Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, R Matao 1226, Sao Paulo, Brazil..
    De Lisio, C.
    Ist Nazl Fis Nucl, Sez Napoli, Via Cintia,Ed G, Naples, Italy..
    Lopez, R. de los Reyes
    Max Planck Inst Kernphys, Saupfercheckweg 1, Heidelberg, Germany..
    De Lotto, B.
    Univ Udine, Via Sci 208, Udine, Italy.;INFN, Sez Trieste, Via Sci 208, Udine, Italy..
    de Naurois, M.
    Ecole Polytech, CNRS, UMR 7638, Lab Leprince Ringuet, Palaiseau, France..
    De Palma, F.
    INFN, Sez Bari, Via Orabona 4, Bari, Italy..
    Del Santo, M.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    Delgado, C.
    CIEMAT, Avda Complutense 40, Madrid, Spain..
    della Volpe, D.
    Univ Geneva, Dept Phys Nucl & Corpusculaire, 24 Rue Gen Dufour, Geneva 4, Switzerland..
    Di Girolamo, T.
    Ist Nazl Fis Nucl, Sez Napoli, Via Cintia,Ed G, Naples, Italy..
    Di Giulio, C.
    INFN, Sez Roma Tor Vergata, Via Ric Sci 1, Rome, Italy..
    Di Pierro, F.
    Ist Nazl Fis Nucl, Sez Torino, Via P Giuria 1, Turin, Italy..
    Di Venere, L.
    Univ Bari, Bari, Italy.;INFN Bari, Bari, Italy..
    Doro, M.
    Univ Padua, Dipartimento Fis, Via Marzolo 8, Padua, Italy..
    Dournaux, J.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Dumas, D.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Dwarkadas, V.
    Univ Chicago, Enrico Fermi Inst, 5640 South Ellis Ave, Chicago, IL 60637 USA..
    Diaz, C.
    CIEMAT, Avda Complutense 40, Madrid, Spain..
    Ebr, J.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Egberts, K.
    Univ Potsdam, Inst Phys & Astron, Golm, Germany..
    Einecke, S.
    TU Dortmund Univ, Dept Phys, Otto Hahn Str 4, Dortmund, Germany..
    Elsaesser, D.
    Univ Wurzburg, Inst Theoret Phys & Astrophys, Campus Hubland Nord,Emil Fischer Str 31, Wurzburg, Germany..
    Eschbach, S.
    Univ Erlangen Nurnberg, Inst Phys, Erwin Rommel Str 1, Erlangen, Germany..
    Falceta-Goncalves, D.
    Univ Sao Paulo, Escola Arles Ciencias & Humanidades, Rua Arlindo Bettio 1000, Sao Paulo, Brazil..
    Fasola, G.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Fedorova, E.
    Taras Shevchenko Natl Univ Kyiv, Astron Observ, 60 Volodymyrska St, Kiev, Ukraine..
    Fernandez-Barral, A.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Ferrand, G.
    RIKEN, Inst Phys & Chem Res, Hirosawa, Wako, Saitama 3510198, Japan..
    Fesquet, M.
    CEA Saclay, CEA, IRFU, SEDI, Bat 141, Gif Sur Yvette, France..
    Fiandrini, E.
    INFN, Sez Perugia, Via A Pascoli, Perugia, Italy..
    Fiasson, A.
    Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, 9 Chemin Bellevue BP 110, Annecy Le Vieux, France..
    Filipovic, M. D.
    Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia..
    Fioretti, V.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    Font, L.
    Univ Autonoma Barcelona, Dept Fis, Unitat Fis Radiac, Bellaterra, Spain.;Univ Autonoma Barcelona, CERES IEEC, Bellaterra, Spain.;Edifici Cc,Campus UAB, Bellaterra, Spain..
    Fontaine, G.
    Ecole Polytech, CNRS, UMR 7638, Lab Leprince Ringuet, Palaiseau, France..
    Franco, F. J.
    Univ Complutense Madrid, Grp Elect, Ave Complutense Madrid, Spain..
    Freixas Coromina, L.
    CIEMAT, Avda Complutense 40, Madrid, Spain..
    Fujita, Y.
    Osaka Univ, Grad Sch Sci, Dept Earth & Space Sci, Toyonaka, Osaka 5600043, Japan..
    Fukui, Y.
    Nagoya Univ, Dept Phys & Astrophys, Chikusa Ku, Nagoya, Aichi 4648602, Japan..
    Funk, S.
    Univ Erlangen Nurnberg, Inst Phys, Erwin Rommel Str 1, Erlangen, Germany..
    Forster, A.
    Max Planck Inst Kernphys, Saupfercheckweg 1, Heidelberg, Germany..
    Gadola, A.
    Univ Zurich, Inst Phys, Winterthurerstr 190, Zurich, Switzerland..
    Lopez, R. Garcia
    Inst Astrofis Canarias, Via Lactea, Tenerife, Spain..
    Garczarczyk, M.
    DESY, Platanenallee 6, Zeuthen, Germany..
    Giglietto, N.
    Politecn Bari, Bari, Italy.;INFN Bari, Bari, Italy..
    Giordano, F.
    Univ Bari, Bari, Italy.;INFN Bari, Bari, Italy..
    Giuliani, A.
    Ist Astrofis Spaziale & Fis Cosm, Via Bassini 15, Milan, Italy..
    Glicenstein, J.
    CEA Saclay, CEA, IRFU, SPP, Bat 141, Gif Sur Yvette, France..
    Gnatyk, R.
    Taras Shevchenko Natl Univ Kyiv, Astron Observ, 60 Volodymyrska St, Kiev, Ukraine..
    Goldoni, P.
    Univ Paris Diderot, APC, CNRS IN2P3, CEA Irfu,Obs Paris,Sorbonne Paris Cite, 10 Rue Alice Domon & Leonie Duquet, Paris 13, France..
    Grabarczyk, T.
    Acad Comp Ctr CYFRONET AGH, Ul Nawojki 11, Krakow, Poland..
    Graciani, R.
    Univ Barcelona, Inst Ciencies Cosmos, IEEC UB, Dept Fis Quant & Astrofis, Marti & Franques 1, Barcelona, Spain..
    Graham, J.
    Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, UK;Univ Durham, Ctr Adv Instrumentat, South Rd, Durham DH1 3LE, UK.
    Grandi, P.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    Granot, J.
    Open Univ Israel, Dept Nat Sci, 1 Univ Rd,POB 808, Raanana, Israel..
    Green, A. J.
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia..
    Griffiths, S.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Gunji, S.
    Yamagata Univ, Dept Phys, Yamagata, Yamagata 9908560, Japan..
    Hakobyan, H.
    Univ Tecn Federico Santa Maria, Ave Espana 1680, Valparaiso, Chile..
    Hara, S.
    Yamanashi Gakuin Univ, Fac Management Informat, Kofu, Yamanashi 4008575, Japan..
    Hassan, T.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Hayashida, M.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan..
    Heller, M.
    Univ Geneva, Dept Phys Nucl & Corpusculaire, 24 Rue Gen Dufour, Geneva 4, Switzerland..
    Helo, J. C.
    Univ Tecn Federico Santa Maria, Ave Espana 1680, Valparaiso, Chile..
    Hinton, J.
    Max Planck Inst Kernphys, Saupfercheckweg 1, Heidelberg, Germany..
    Hnatyk, B.
    Taras Shevchenko Natl Univ Kyiv, Astron Observ, 60 Volodymyrska St, Kiev, Ukraine..
    Huet, J.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Huetten, M.
    DESY, Platanenallee 6, Zeuthen, Germany..
    Humensky, T. B.
    Columbia Univ, Dept Phys, 538 West 120th St, New York, NY 10027 USA..
    Hussein, M.
    Univ Manitoba, 540 Machray Hall, Winnipeg, MB R3T 2N2, Canada..
    Horandel, J.
    Radboud Univ Nijmegen, POB 9010, GL Nijmegen, Netherlands..
    Ikeno, Y.
    Tokai Univ, Dept Phys, Kita Kaname, Hiratsuka, Kanagawa 2591292, Japan..
    Inada, T.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan..
    Inome, Y.
    Konan Univ, Dept Phys, Kobe, Hyogo 6588501, Japan..
    Inoue, S.
    RIKEN, Inst Phys & Chem Res, Hirosawa, Wako, Saitama 3510198, Japan..
    Inoue, T.
    Natl Astron Observ Japan, Div Theoret Astron, Osawa Mitaka, Tokyo 1818588, Japan..
    Inoue, Y.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Chuo Ku, Yoshinodai, Sagamihara, Kanagawa 2525210, Japan..
    Ioka, K.
    Kyoto Univ, Yukawa Inst Theoret Phys, Kyoto 6068502, Japan..
    Iori, M.
    INFN, Sez Roma La Sapienza, Ple Aldo Moro 2, Rome, Italy..
    Jacquemier, J.
    Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, 9 Chemin Bellevue BP 110, Annecy Le Vieux, France..
    Janecek, P.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Jankowsky, D.
    Univ Erlangen Nurnberg, Inst Phys, Erwin Rommel Str 1, Erlangen, Germany..
    Jung, I.
    Univ Erlangen Nurnberg, Inst Phys, Erwin Rommel Str 1, Erlangen, Germany..
    Kaaret, P.
    Univ Iowa, Dept Phys & Astron, Van Allen Hall, Iowa City, IA 52242 USA..
    Katagiri, H.
    Ibaraki Univ, Fac Sci, Mito, Ibaraki 3108512, Japan..
    Kimeswenger, S.
    Univ Catolica Norte, Ave Angamos 0610, Antofagasta, Chile..
    Kimura, S.
    Tokai Univ, Dept Phys, Kita Kaname, Hiratsuka, Kanagawa 2591292, Japan..
    Knodlseder, J.
    IRAP, 9 Ave Colonel Roche,BP 44346, Toulouse 4, France..
    Koch, B.
    Pontificia Univ Catolica Chile, Avda Libertador Bernardo OHiggins 340, Santiago, Chile..
    Kocot, J.
    Acad Comp Ctr CYFRONET AGH, Ul Nawojki 11, Krakow, Poland..
    Kohri, K.
    KEK High Energy Accelerator Org, Inst Particle & Nucl Studies, Oho, Tsukuba, Ibaraki 3050801, Japan..
    Komin, N.
    Univ Witwatersrand, 1 Jan Smuts Ave,Johannesburg, South Africa..
    Konno, Y.
    Kyoto Univ, Grad Sch Sci, Div Phys & Astron, Sakyo Ku, Kyoto 6068502, Japan..
    Kosack, K.
    CEA Saclay, CEA, IRFU, SAp, Bat 709, Gif Sur Yvette, France..
    Koyama, S.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Chuo Ku, Yoshinodai, Sagamihara, Kanagawa 2525210, Japan..
    Kraus, M.
    Univ Erlangen Nurnberg, Inst Phys, Erwin Rommel Str 1, Erlangen, Germany..
    Kubo, H.
    Kyoto Univ, Grad Sch Sci, Div Phys & Astron, Sakyo Ku, Kyoto 6068502, Japan..
    Mezek, G. Kukec
    Univ Nova Gorica, Lab Astroparticle Phys, Vipayska 13, Nova Gorica 5000, Slovenia..
    Kushida, J.
    Tokai Univ, Dept Phys, Kita Kaname, Hiratsuka, Kanagawa 2591292, Japan..
    La Palombara, N.
    Ist Astrofis Spaziale & Fis Cosm, Via Bassini 15, Milan, Italy..
    Lalik, K.
    Polish Acad Sci, Henryk Niewodniczanski Inst Nucl Phys, Ul Radzikowskiego 152, Krakow, Poland..
    Lamanna, G.
    Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, 9 Chemin Bellevue BP 110, Annecy Le Vieux, France..
    Landt, H.
    Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, UK;Univ Durham, Ctr Adv Instrumentat, South Rd, Durham DH1 3LE, UK.
    Lapington, J.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, UK.
    Laporte, P.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, F-92190 Meudon, France..
    Lee, S.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Chuo Ku, Yoshinodai, Sagamihara, Kanagawa 2525210, Japan..
    Lees, J.
    Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, 9 Chemin Bellevue BP 110, Annecy Le Vieux, France..
    Lefaucheur, J.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Lenain, J. -P
    Leto, G.
    INAF Osservatorio Astrofis Catania, Via S Sofia 78, Catania, Italy..
    Lindfors, E.
    Univ Turku, Tuorla Observ, Piikkio, Finland..
    Lohse, T.
    Humboldt Univ, Dept Phys, Newtonstr 15, Berlin, Germany..
    Lombardi, S.
    Osserv Astron Roma, INAF, Via Frascati 33, Monte Porzio Catone, Italy..
    Longo, F.
    Univ Trieste, Trieste, Italy.;INFN, Sezione Trieste, Trieste, Italy..
    Lopez, M.
    Univ Complutense Madrid, Grp Altas Energias, Av Complutense S-N, Madrid, Spain..
    Lucarelli, F.
    Osserv Astron Roma, INAF, Via Frascati 33, Monte Porzio Catone, Italy..
    Luque-Escamilla, P. L.
    Univ Jaen, Escuela Politecn Super Jaen, Campus Las Lagunillas, Edif A3, Jaen, Spain..
    Lopez-Coto, R.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Maccarone, M. C.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    Maier, G.
    DESY, Platanenallee 6, Zeuthen, Germany..
    Malaguti, G.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    Mandat, D.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Maneva, G.
    BAS, Inst Nucl Res & Nucl Energy, 72 Blvd Tsarigradsko Chaussee, Sofia 1784, Bulgaria..
    Mangano, S.
    CIEMAT, Avda Complutense 40, Madrid, Spain..
    Marcowith, A.
    Univ Montpellier, CNRS, IN2P3, Lab Univers & Particules Montpellier, CC 72,Pl Eugene Bataillon, Montpellier 5, France..
    Marti, J.
    Univ Jaen, Escuela Politecn Super Jaen, Campus Las Lagunillas,Edif A3, Jaen, Spain..
    Martinez, M.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB,Bellaterra, Barcelona, Spain..
    Martinez, G.
    CIEMAT, Avda Complutense 40, Madrid, Spain..
    Masuda, S.
    Kyoto Univ, Grad Sch Sci, Div Phys & Astron, Sakyo Ku, Kyoto 6068502, Japan..
    Maurin, G.
    Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, 9 Chemin Bellevue BP 110, Annecy Le Vieux, France..
    Maxted, N.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia..
    Melioli, C.
    Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, R Matao 1226, Sao Paulo, Brazil..
    Mineo, T.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    Mirabal, N.
    Univ Complutense Madrid, Grp Altas Energias, Av Complutense Madrid, Spain..
    Mizuno, T.
    Hiroshima Univ, Hiroshima Astrophys Sci Ctr, Hiroshima 7398526, Japan..
    Moderski, R.
    Polish Acad Sci, Copernicus Astron Ctr, Ul Bartycka 18, Warsaw, Poland..
    Mohammed, M.
    Heidelberg Univ, Landessternwarte, Heidelberg, Germany..
    Montaruli, T.
    Univ Geneva, Dept Phys Nucl & Corpusculaire, 24 Rue Gen Dufour, Geneva 4, Switzerland..
    Moralejo, A.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Mori, K.
    Miyazaki Univ, Dept Appl Phys, Gakuen Kibana Dai Nishi, Miyazaki 8892192, Japan..
    Morlino, G.
    Univ Aquila, Dipartimento Sci Fis & Chim, INFN, Via Vetoio 1, Laquila, Italy.;Gran Sasso Sci Inst, Via Vetoio 1, Laquila, Italy..
    Morselli, A.
    INFN, Sez Roma Tor Vergata, Via Ric Sci 1, Italy..
    Moulin, E.
    CEA Saclay, CEA, IRFU, SPP, Bat 141, Gif Sur Yvette, France..
    Mukherjee, R.
    Columbia Univ, Dept Phys, 538 West 120th St, New York, NY 10027 USA..
    Mundell, C.
    Univ Bath, Bath BA2 7AY, Avon, UK.
    Muraishi, H.
    Kitasato Univ, Sch Allied Hlth Sci, Sagamihara, Kanagawa 2288555, Japan..
    Murase, K.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan..
    Nagataki, S.
    RIKEN, Inst Phys & Chem Res, Hirosawa, Wako, Saitama 3510198, Japan..
    Nagayoshi, T.
    Saitama Univ, Grad Sch Sci & Engn, Sakura Ku, 255 Simo Ohkubo, Saitama City, Saitama 3388570, Japan..
    Naito, T.
    Yamanashi Gakuin Univ, Fac Management Informat, Kofu, Yamanashi 4008575, Japan..
    Nakajima, D.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan.;Max Planck Inst Phys & Astrophys, Fohringer Ring 6, Munich, Germany..
    Nakamori, T.
    Yamagata Univ, Dept Phys, Yamagata, Yamagata 9908560, Japan..
    Nemmen, R.
    Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, R Matao 1226, Sao Paulo, Brazil..
    Niemiec, J.
    Polish Acad Sci, Henryk Niewodniczanski Inst Nucl Phys, Ul Radzikowskiego 152, Krakow, Poland..
    Nieto, D.
    Columbia Univ, Dept Phys, 538 West 120th St, New York, NY 10027 USA..
    Nievas-Rosillo, M.
    Univ Complutense Madrid, Grp Altas Energias, Av Complutense, Madrid, Spain..
    Nikolajuk, M.
    Univ Bialystok, Fac Phys, Ul K Ciolkowskiego 1L, Bialystok, Poland..
    Nishijima, K.
    Tokai Univ, Dept Phys, Kita Kaname, Hiratsuka, Kanagawa 2591292, Japan..
    Noda, K.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan.;Max Planck Inst Phys & Astrophys, Fohringer Ring 6, Munich, Germany..
    Nogues, L.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Nosek, D.
    Charles Univ Prague, Inst Particle & Nucl Phys, V Holesovickach 2, Prague 18000 8, Czech Republic..
    Novosyadlyj, B.
    Ivan Franko Natl Univ Lviv, Astron Observ, 1 Univ Ska St, City Of Lviv, Ukraine..
    Nozaki, S.
    Kyoto Univ, Grad Sch Sci, Div Phys & Astron, Sakyo Ku, Kyoto 6068502, Japan..
    Ohira, Y.
    Aoyama Gakuin Univ, Dept Math & Phys, Sagamihara, Kanagawa 2298558, Japan..
    Ohishi, M.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan..
    Ohm, S.
    DESY, Platanenallee 6, Zeuthen, Germany..
    Okumura, A.
    Nagoya Univ, Inst Space Earth Environm Res, Chikusa Ku, Nagoya, Aichi 4648601, Japan..
    Ong, R. A.
    Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Orito, R.
    Tokushima Univ, Grad Sch Sci & Technol, Tokushima 7708506, Japan..
    Orlati, A.
    INAF IRA, INAF, Ist Radioastron, Via Gobetti 101, Bologna, Italy..
    Ostrowski, M.
    Jagiellonian Univ, Fac Phys Astron & Appl Comp Sci, Ul Prof Stanislawa Lojasiewicza 11, Krakow, Poland..
    Oya, I.
    DESY, Platanenallee 6, Zeuthen, Germany..
    Padovani, M.
    Univ Montpellier, CNRS, IN2P3, Lab Univers & Particules Montpellier, CC 72,Pl Eugene Bataillon, Montpellier 5, France..
    Palacio, J.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Palatka, M.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Paredes, J. M.
    Univ Barcelona, Inst Ciencies Cosmos, IEEC UB, Dept Fis Quant & Astrofis, Marti & Franques 1, Barcelona, Spain..
    Pavy, S.
    Ecole Polytech, CNRS, UMR 7638, Lab Leprince Ringuet, Palaiseau, France..
    Pe'er, A.
    Max Planck Inst Phys & Astrophys, Fohringer Ring 6, Munich, Germany..
    Persic, M.
    Univ Udine, Via Sci 208, Udine, Italy.;INFN, Sez Trieste, Via Sci 208, Udine, Italy.;Osserv Astron Trieste, Via Sci 208, Udine, Italy.;Ist Nazl Fis Nucl, Sez Trieste, Via Sci 208, Udine, Italy..
    Petrucci, P.
    Univ Joseph Fourier, INSU CNRS, Inst Planetol & Astrophys Grenoble, 621 Ave Cent,Domaine Univ, Grenoble 9, France..
    Petruk, O.
    Inst Appl Problems Mech & Math, 3B Naukova St, Lvov, Ukraine..
    Pisarski, A.
    Univ Bialystok, Fac Phys, Ul K Ciolkowskiego 1L, Bialystok, Poland..
    Pohl, M.
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str, Golm, Germany..
    Porcelli, A.
    Univ Geneva, Dept Phys Nucl & Corpusculaire, 24 Rue Gen Dufour, Geneva 4, Switzerland..
    Prandini, E.
    Univ Geneva, Observ Geneva, ISDC Data Ctr Astrophys, Chemin Ecogia 16, Versoix, Switzerland..
    Prast, J.
    Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, 9 Chemin Bellevue BP 110, Annecy Le Vieux, France..
    Principe, G.
    Univ Erlangen Nurnberg, Inst Phys, Erwin Rommel Str 1,Erlangen, Germany..
    Prouza, M.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Pueschel, E.
    Univ Coll Dublin, Dublin 4, Ireland..
    Puelhofer, G.
    Univ Tubingen, Inst Astron & Astrophys, Sand 1, Tubingen, Germany..
    Quirrenbach, A.
    Heidelberg Univ, Landessternwarte, Heidelberg, Germany..
    Rameez, M.
    Univ Geneva, Dept Phys Nucl & Corpusculaire, 24 Rue Gen Dufour, Geneva 4, Switzerland..
    Reimer, O.
    Leopold Franzens Univ, Inst Astro & Teilchenphys, Technikerstr , Innsbruck, Austria..
    Renaud, M.
    Univ Montpellier, CNRS, IN2P3, Lab Univers & Particules Montpellier, CC 72,Pl Eugene Bataillon, Montpellier 5, France..
    Ribo, M.
    Univ Barcelona, Inst Ciencies Cosmos, IEEC UB, Dept Fis Quant & Astrofis, Marti & Franques 1, Barcelona, Spain..
    Rico, J.
    IFAE, Barcelona Inst Sci & Technol, Campus UAB, Bellaterra, Barcelona, Spain..
    Rizi, V.
    Univ Aquila, Dipartimento Sci Fis & Chim, INFN, Via Vetoio 1, Laquila, Italy.;Gran Sasso Sci Inst, Via Vetoio 1, Laquila, Italy..
    Rodriguez, J.
    CEA Saclay, CEA, IRFU, SAp, Bat 709, Gif Sur Yvette, France..
    Fernandez, G. Rodriguez
    INFN, Sez Roma Tor Vergata, Via Ric Sci 1, Rome, Italy..
    Rodriguez Vazquez, J. J.
    CIEMAT, Avda Complutense 40, Madrid, Spain..
    Romano, P.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    Romeo, G.
    INAF Osservatorio Astrofis Catania, Via S Sofia 78, Catania, Italy..
    Rosado, J.
    Univ Complutense Madrid, Grp Altas Energias, Av Complutense, Madrid, Spain..
    Rousselle, J.
    Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Rowell, G.
    Univ Adelaide, Sch Phys Sci, Adelaide, SA 5005, Australia..
    Rudak, B.
    Polish Acad Sci, Copernicus Astron Ctr, Ul Bartycka 18, Warsaw, Poland..
    Sadeh, I.
    DESY, Platanenallee 6, Zeuthen, Germany..
    Safi-Harb, S.
    Univ Manitoba, 540 Machray Hall, Winnipeg, MB R3T 2N2, Canada..
    Saito, T.
    Kyoto Univ, Grad Sch Sci, Div Phys & Astron, Sakyo Ku, Kyoto 6068502, Japan..
    Sakaki, N.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan..
    Sanchez, D.
    Univ Savoie, CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, 9 Chemin Bellevue BP 110, Annecy Le Vieux, France..
    Sangiorgi, P.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    Sano, H.
    Nagoya Univ, Dept Phys & Astrophys, Chikusa Ku, Nagoya, Aichi 4648602, Japan..
    Santander, M.
    Columbia Univ, Dept Phys, 538 West 120th St, New York, NY 10027 USA..
    Sarkar, S.
    Univ Oxford, Dept Phys, 1 Keble Rd, Oxford OX1 3NP, UK.
    Sawada, M.
    Aoyama Gakuin Univ, Dept Math & Phys, Sagamihara, Kanagawa 2298558, Japan..
    Schioppa, E. J.
    Univ Geneva, Dept Phys Nucl & Corpusculaire, 24 Rue Gen Dufour, Geneva 4, Switzerland..
    Schoorlemmer, H.
    Max Planck Inst Kernphys, Saupfercheckweg 1, Heidelberg, Germany..
    Schovanek, P.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Schussler, F.
    CEA Saclay, CEA, IRFU, SPP, Bat 141, Gif Sur Yvette, France..
    Sergijenko, O.
    Ivan Franko Natl Univ Lviv, Astron Observ, 1 Univ Ska St, City Of Lviv, Ukraine..
    Servillat, M.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Shalchi, A.
    Univ Manitoba, 540 Machray Hall, Winnipeg, MB R3T 2N2, Canada..
    Shellard, R. C.
    Ctr Brasileiro Pesquisas Fis, Rua Xavier Sigaud 150, Rio De Janeiro, Brazil..
    Siejkowski, H.
    Acad Comp Ctr CYFRONET AGH, Ul Nawojki 11, Krakow, Poland..
    Sillanpaa, A.
    Univ Turku, Tuorla Observ, Piikkio, Finland..
    Simone, D.
    INFN, Sez Bari, Via Orabona 4, Bari, Italy..
    Sliusar, V.
    Univ Geneva, Observ Geneva, ISDC Data Ctr Astrophys, Chemin Ecogia 16, Versoix, Switzerland..
    Sol, H.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Stanic, S.
    Univ Nova Gorica, Lab Astroparticle Phys, Vipayska 13, Nova Gorica 5000, Slovenia..
    Starling, R.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, UK.
    Stawarz, L.
    Jagiellonian Univ, Fac Phys Astron & Appl Comp Sci, Ul Prof Stanislawa Lojasiewicza 11, Krakow, Poland..
    Stefanik, S.
    Charles Univ Prague, Inst Particle & Nucl Phys, V Holesovickach 2, Prague 18000 8, Czech Republic..
    Stephan, M.
    Univ Amsterdam, Astron Inst Anton Pannekoek, Sci Pk 904, XH Amsterdam, Netherlands..
    Stolarczyk, T.
    CEA Saclay, CEA, IRFU, SAp, Bat 709, Gif Sur Yvette, France..
    Szanecki, M.
    Univ Lodz, Fac Phys & Appl Comp Sci, Ul Pomorska Lodz, Poland..
    Szepieniec, T.
    Acad Comp Ctr CYFRONET AGH, Ul Nawojki 11, Krakow, Poland..
    Tagliaferri, G.
    INAF Osservatorio Astron Brera, Via Brera 28, Milan, Italy..
    Tajima, H.
    Nagoya Univ, Inst Space Earth Environm Res, Chikusa Ku, Nagoya, Aichi 4648601, Japan..
    Takahashi, M.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan..
    Takeda, J.
    Yamagata Univ, Dept Phys, Yamagata, Yamagata 9908560, Japan..
    Tanaka, M.
    KEK High Energy Accelerator Org, Inst Particle & Nucl Studies, Oho, Tsukuba, Ibaraki 3050801, Japan..
    Tanaka, S.
    Konan Univ, Dept Phys, Kobe, Hyogo 6588501, Japan..
    Tejedor, L. A.
    Univ Complutense Madrid, Grp Altas Energias, Av Complutense, Madrid, Spain..
    Telezhinsky, I.
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str, Golm, Germany..
    Temnikov, P.
    BAS, Inst Nucl Res & Nucl Energy, 72 Blvd Tsarigradsko Chaussee, Sofia 1784, Bulgaria..
    Terada, Y.
    Saitama Univ, Grad Sch Sci & Engn, Sakura Ku, 255 Simo Ohkubo, Saitama City, Saitama 3388570, Japan..
    Tescaro, D.
    Univ Padua, Dipartimento Fis, Via Marzolo 8, Padua, Italy..
    Teshima, M.
    Univ Tokyo, Inst Cosm Ray Res, Kashi Wwanoha, Kashiwa, Chiba 2778582, Japan.;Max Planck Inst Phys & Astrophys, Fohringer Ring 6, Munich, Germany..
    Testa, V.
    Osserv Astron Roma, INAF, Via Frascati 33, Monte Porzio Catone, Italy..
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Tokanai, F.
    Yamagata Univ, Dept Phys, Yamagata, Yamagata 9908560, Japan..
    Torres, D. F.
    Inst Space Sci IEEC CSIC, Campus UAB,Caner Can Magrans Cerdanyola Del Valles, Spain.;ICREA, Campus UAB,Caner Can Magrans Cerdanyola Del Valles, Spain..
    Torresi, E.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    Tosti, G.
    INAF Osservatorio Astron Brera, Via Brera 28, Milan, Italy..
    Townsley, C.
    Cherenkov Telescope Array Observ, Saupfercheckweg 1, Heidelberg, Germany..
    Travnicek, P.
    Acad Sci Czech Republic, Inst Phys, Slovance Prague 18221 8, Czech Republic..
    Trichard, C.
    Aix Marseille Univ, CNRS, IN2P3, CPPM, 163 Ave Luminy, Marseille, France..
    Trifoglio, M.
    Ist Astrofis Spaziale & Fis Cosm Bologna, Via Piero Gobetti 101, Bologna, Italy..
    Tsujimoto, S.
    Tokai Univ, Dept Phys, Kita Kaname, Hiratsuka, Kanagawa 2591292, Japan..
    Vagelli, V.
    INFN, Sez Perugia, Via A Pascoli, Perugia, Italy..
    Vallania, P.
    Osserv Astron Torino, INAF, Corso Fiume 4, Turin, Italy..
    Valore, L.
    Ist Nazl Fis Nucl, Sez Napoli, Via Cintia,Ed G, Naples, Italy..
    van Driel, W.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    van Eldik, C.
    Univ Erlangen Nurnberg, Inst Phys, Erwin Rommel Str 1, Erlangen, Germany..
    Vandenbroucke, J.
    Univ Wisconsin, 500 Lincoln Dr, Madison, WI 53706 USA..
    Vassiliev, V.
    Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Vecchi, M.
    Univ Sao Paulo, Inst Fis Sao Carlos, Ave Trabalhador Sao Carlense 400, Sao Carlos, SP, Brazil..
    Vercellone, S.
    INAF Ist Astrofis Spaziale & Fis Cosm Palermo, Via U La Malfa 153, Palermo, Italy..
    Vergani, S.
    Observ Paris, CNRS, LUTH, 5 Pl Jules Janssen, Meudon, France.;Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, Meudon, France..
    Vigorito, C.
    Ist Nazl Fis Nucl, Sez Torino, Via P Giuria 1, Turin, Italy..
    Vorobiov, S.
    Univ Nova Gorica, Lab Astroparticle Phys, Vipayska 13, Nova Gorica 5000, Slovenia..
    Vrastil, M.
    Acad Sci Czech Republic, Inst Phys, Slovance, Prague 18221 8, Czech Republic..
    Vazquez Acosta, M. L.
    Inst Astrofis Canarias, Via Lactea, Tenerife, Spain..
    Wagner, S. J.
    Heidelberg Univ, Landessternwarte, Heidelberg, Germany..
    Wagner, R.
    Max Planck Inst Phys & Astrophys, Fohringer Ring 6, Munich, Germany.;Stockholm Univ, Univ Vagen 10 A, Stockholm, Sweden..
    Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-39462017In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 840, no 2, article id 74Article in journal (Refereed)
    Abstract [en]

    We perform simulations for future Cherenkov Telescope Array (CTA) observations of RX J1713.7-3946, a young supernova remnant (SNR) and one of the brightest sources ever discovered in very high energy (VHE) gamma rays. Special attention is paid to exploring possible spatial (anti) correlations of gamma rays with emission at other wavelengths, in particular X-rays and CO/H I emission. We present a series of simulated images of RX J1713.7-3946 for CTA based on a set of observationally motivated models for the gamma-ray emission. In these models, VHE gamma rays produced by high-energy electrons are assumed to trace the nonthermal X-ray emission observed by XMM-Newton, whereas those originating from relativistic protons delineate the local gas distributions. The local atomic and molecular gas distributions are deduced by the NANTEN team from CO and H I observations. Our primary goal is to show how one can distinguish the emission mechanism(s) of the gamma rays (i.e., hadronic versus leptonic, or a mixture of the two) through information provided by their spatial distribution, spectra, and time variation. This work is the first attempt to quantitatively evaluate the capabilities of CTA to achieve various proposed scientific goals by observing this important cosmic particle accelerator.

  • 2.
    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, 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.

  • 3.
    Becherini, Yvonne
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Bylund, Tomas
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Ernenwein, Jean-Pierre
    Aix Marseille Univ, France.
    Kukec Mezek, Gasper
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Punch, Michael
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Univ Paris, France.
    Romano, Patrizia
    INAF-Osservatorio Astronomico di Brera, Italy.
    Saleh, Ahmed
    Khalifa University, United Arab Emirates.
    Senniappan, Mohanraj
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Thoudam, Satyendra
    Khalifa University, United Arab Emirates.
    Tluczykont, Martin
    Universität Hamburg, Germany.
    Vercellone, Stefano
    INAF-Osservatorio Astronomico di Brera, Italy.
    The CoMET multiperspective event tracker for wide field-of-view gamma-ray astronomy2022In: Proceedings of Science: 37th International Cosmic Ray Conference (ICRC 2021), July 12th – 23rd, 2021 Online – Berlin, German, Scuola Internazionale Superiore di Studi Avanzati (SISSA) , 2022, Vol. 395, article id 905Conference paper (Refereed)
    Abstract [en]

    The ALTO project aims to build a particle detector array for very high energy gamma ray observations optimized for soft spectrum sources. The accurate reconstruction of gamma ray events, in particular their energies, using a surface array is an especially challenging problem at the low energies ALTO aims to optimize for. In this contribution, we leverage Convolutional Neural Networks (CNNs) to improve reconstruction performance at lower energies ( smaller 1 TeV ) as compared to the SEMLA analysis procedure, which is a more traditional method using mainly manually derived features.rnWe present performance figures using different network architectures and training settings, both in terms of accuracy and training time, as well as the impact of various data augmentation techniques.

    Download full text (pdf)
    fulltext
  • 4.
    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.

  • 5.
    Bonardi, A.
    et al.
    Radboud University, Netherlands.
    Buitink, S.
    Vrije Universiteit Brussel, Belgium.
    Corstanje, A.
    Radboud University, Netherlands.
    Falcke, H.
    Radboud University, Netherlands;NIKHEF, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Hare, B. M.
    University Groningen, Netherlands.
    Hörandel, J. R.
    Radboud University, Netherlands;NIKHEF, Netherlands.
    Mitra, P.
    Vrije Universiteit Brussel, Belgium.
    Mulrey, K.
    Vrije Universiteit Brussel, Belgium.
    Nelles, A.
    Radboud University, Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, Netherlands.
    Rossetto, L.
    Radboud University, Netherlands.
    Schellart, P.
    Radboud University, Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, Netherlands;Vrije Universiteit Brussel, Belgium.
    Ter Veen, S.
    Radboud University, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, Netherlands.
    Trinh, T. N. G.
    University Groningen, 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).

  • 6.
    Bonardi, Antonio
    et al.
    Radboud Univ Nijmegen, Netherlands.
    Buitink, Stijn
    Vrije Univ Brussel, Belgium.
    Corstanje, Arthur
    Radboud Univ Nijmegen, Netherlands.
    Falcke, Heino
    Radboud Univ Nijmegen, Netherlands;NIKHEF, Netherlands;Netherlands Inst Radio Astron ASTRON, Netherlands.
    Hare, Brian M.
    Univ Groningen, Netherlands.
    Horande, Jorg R.
    Radboud Univ Nijmegen, Netherlands;NIKHEF, Netherlands.
    Mitra, Pragati
    Vrije Univ Brussel, Belgium.
    Mulrey, Katie
    Vrije Univ Brussel, Belgium.
    Nelles, Anna
    DESY, Germany;Humboldt Univ, Germany.
    Rachen, Jorg P.
    Radboud Univ Nijmegen, Netherlands.
    Rossetto, Laura
    Radboud Univ Nijmegen, Netherlands.
    Schellart, Pim
    Princeton Univ, USA.
    Scholten, Olaf
    Univ Groningen, Netherlands;Vrije Univ Brussel, Belgium.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Trinh, Gia T. N.
    Univ Groningen, Netherlands.
    Veen, Sanderter
    Netherlands Inst Radio Astron ASTRON, Netherlands.
    Winchen, Tobias
    Vrije Univ Brussel, Belgium.
    Towards real-time cosmic-ray identification with the LOw Frequency ARay2019In: 8th International Conference on Acoustic and Radio EeV Neutrino Detection Activities (ARENA 2018) / [ed] Riccobene, G Biagi, S Capone, A Distefano, C Piattelli, P, EDP Sciences , 2019, p. 1-3, article id 04005Conference paper (Refereed)
    Abstract [en]

    The radio signals emitted by Extensive Air Showers have been successfully used for the last decade by LOFAR to reconstruct the properties of the primary cosmic rays. Since an effective real-time recognition system for the very short radio pulses is lacking, cosmic-ray acquisition is currently triggered by an external array of particle detector, called LORA, limiting the LOFAR collecting area to the area covered by LORA. A new algorithm for the real-time cosmic-ray detection has been developed for the LOFAR Low Band Antenna, which are sensitive between 10 and 90 MHz, and is here presented together with the latest results.

  • 7.
    Borwankar, Chinmay
    et al.
    Bhabha Atom Res Ctr, India.
    Bhatt, Nilay
    Bhabha Atom Res Ctr, India.
    Bhattacharyya, Subir
    Bhabha Atom Res Ctr, India.
    Rannot, R. C.
    Bhabha Atom Res Ctr, India.
    Tickoo, A. K.
    Bhabha Atom Res Ctr, India.
    Koul, R.
    Bhabha Atom Res Ctr, India.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Simulation studies of MACE-I: Trigger rates and energy thresholds2016In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 84, p. 97-106Article in journal (Refereed)
    Abstract [en]

    The MACE (Major Atmospheric Cherenkov Experiment) is an upcoming Very High Energy (VHE) gamma-ray telescope, based on imaging atmospheric Cherenkov technique, being installed at Hanle, a high altitude astronomical site in Ladakh, India. Here we present Monte Carlo simulation studies of trigger rates and threshold energies of MACE in the zenith angle range of 0 degrees-60 degrees for on-axis gamma-ray coming from point source and various cosmic ray species. We have simulated the telescope's response to gamma-rays, proton, electron and alpha initiated atmospheric Extensive Air Showers (EAS) in the broad energy range of 5 GeV to 20 TeV. For gamma-rays we consider power law and log parabolic spectra while other particles are simulated with their respective cosmic ray spectrum. Trigger rates and threshold energies are estimated for the trigger configuration of 4 Close Cluster Nearest Neighbour(CCNN) pixels as implemented in MACE hardware, in combination with single channel discriminator threshold ranging from 6-10 photo electrons (pe). We find that MACE can achieve the gamma-ray trigger energy threshold of similar to 17 GeV (4 CCNN, 9 pe) at 0 degrees zenith angle for power law spectrum. The total trigger rate at 0 degrees zenith is expected to be similar to 650 Hz, with protons contributing similar to 80% to it. For the zenith range of 0 degrees-40 degrees we find that the telescope can achieve gamma-gray trigger threshold energies of similar to 22 GeV at 20 degrees zenith angle and similar to 40 GeV at 40 degrees zenith angle. Integral rates are also almost constant for this zenith angle range. At zenith angle of 60 degrees, trigger energy threshold increases to similar to 173 GeV and total integral rate falls down to similar to 305 Hz. (C) 2016 Elsevier B.V. All rights reserved.

  • 8.
    Buitink, S.
    et al.
    Vrije Universiteit Brussel, Belgium.
    Bonardi, A.
    Radboud University, Netherlands.
    Corstanje, A.
    Radboud University, Netherlands.
    Falcke, H.
    Radboud University, Netherlands;NIKHEF, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Hare, B. M.
    University Groningen, Netherlands.
    Hörandel, J. R.
    Vrije Universiteit Brussel, Belgium;NIKHEF, Netherlands.
    Mitra, P.
    Vrije Universiteit Brussel, Belgium.
    Mulrey, K.
    Vrije Universiteit Brussel, Belgium.
    Nelles, A.
    Radboud University, Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, Netherlands.
    Rossetto, L.
    Radboud University, Netherlands.
    Schellart, P.
    Radboud University, Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, Netherlands;Vrije Universiteit Brussel, Belgium.
    Ter Veen, S.
    Radboud University, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, Netherlands.
    Trinh, T. N. G.
    University Groningen, 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 < 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).

  • 9.
    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.

  • 10.
    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.

  • 11.
    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.

  • 12.
    Bylund, Tomas
    et al.
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Kukec Mezek, Gasper
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Senniappan, Mohanraj
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Becherini, Yvonne
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Punch, Michael
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Univ Paris, France.
    Thoudam, Satyendra
    Khalifa University, United Arab Emirates.
    Ernenwein, Jean-Pierre
    Aix Marseille Univ, France.
    Studies of Gamma-Ray Shower Reconstruction UsingDeep Learning2021In: Proceedings of Science: 37th International Cosmic Ray Conference (ICRC 2021), July 12th – 23rd, 2021 Online – Berlin, German, 2021, article id 758Conference paper (Refereed)
    Abstract [en]

    The ALTO project aims to build a particle detector array for very high energy gamma ray observations optimized for soft spectrum sources. The accurate reconstruction of gamma ray events, in particular their energies, using a surface array is an especially challenging problem at the low energies ALTO aims to optimize for. In this contribution, we leverage Convolutional Neural Networks (CNNs) to improve reconstruction performance at lower energies ( smaller 1 TeV ) as compared to the SEMLA analysis procedure, which is a more traditional method using mainly manually derived features.rnWe present performance figures using different network architectures and training settings, both in terms of accuracy and training time, as well as the impact of various data augmentation techniques.

  • 13. 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.

  • 14.
    Corstanje, A.
    et al.
    Radboud University Nijmegen, Netherlands.
    Bonardi, A.
    Radboud University Nijmegen, Netherlands.
    Buitink, S.
    Radboud University Nijmegen, Netherlands ; Vrije Universiteit Brussel, Belgium.
    Falcke, H.
    Radboud University Nijmegen, Netherlands ; ASTRON Netherlands Institute for Radio Astronomy, Netherlands ; Nikhef, Sci Pk Amsterdam, NL-1098 XG Amsterdam, Netherlands.;Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany..
    Horandel, J. R.
    Radboud University Nijmegen, Netherlands ;Nikhef, Sci Pk Amsterdam, NL-1098 XG Amsterdam, Netherlands..
    Mitra, R.
    Vrije Univ Brussel, Inst Astrophys, Pleinlaan 2, B-1050 Brussels, Belgium..
    Mulrey, K.
    Vrije Univ Brussel, Inst Astrophys, Pleinlaan 2, B-1050 Brussels, Belgium..
    Nelles, A.
    Radboud University Nijmegen, Netherlands ;Nikhef, Sci Pk Amsterdam, NL-1098 XG Amsterdam, Netherlands.;Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA..
    Rachen, J. P.
    Radboud University Nijmegen, Netherlands.
    Rossetto, L.
    Radboud University Nijmegen, Netherlands.
    Schellart, P.
    Radboud University Nijmegen, Netherlands ;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA..
    Scholten, O.
    Vrije Univ Brussel, Interuniv Inst High Energy, Pleinlaan 2, B-1050 Brussels, Belgium.;Univ Groningen, POB 72, NL-9700 AB Groningen, Netherlands..
    ter Veen, S.
    Radboud University Nijmegen, Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University Nijmegen, Netherlands.
    Trinh, G.
    Univ Groningen, POB 72, NL-9700 AB Groningen, Netherlands..
    Winchen, T.
    Vrije Univ Brussel, Inst Astrophys, Pleinlaan 2, B-1050 Brussels, Belgium..
    The effect of the atmospheric refractive index on the radio signal of extensive air showers2017In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 89, p. 23-29Article in journal (Refereed)
    Abstract [en]

    For the interpretation of measurements of radio emission from extensive air showers, an important systematic uncertainty arises from natural variations of the atmospheric refractive index n. At a given altitude, the refractivity N = 10(6) (n - 1) can have relative variations on the order of 10% depending on temperature, humidity, and air pressure. Typical corrections to be applied to N are about 4%. Using CoREAS simulations of radio emission from air showers, we have evaluated the effect of varying N on measurements of the depth of shower maximum X-max. For an observation band of 30-80 MHz, a difference of 4% in refractivity gives rise to a systematic error in the inferred X-max between 3.5 and 11 g/cm(2), for proton showers with zenith angles ranging from 15 to 50 degrees. At higher frequencies, from 120 to 250 MHz, the offset ranges from 10 to 22 g/cm(2). These offsets were found to be proportional to the geometric distance to X-max. We have compared the results to a simple model based on the Cherenkov angle. For the 120-250 MHz band, the model is in qualitative agreement with the simulations. In typical circumstances, we find a slight decrease in X-max compared to the default refractivity treatment in CoREAS. While this is within commonly treated systematic uncertainties, accounting for it explicitly improves the accuracy of X-max measurements. (C) 2017 Elsevier B.V. All rights reserved.

  • 15.
    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.

  • 16.
    Corstanje, A.
    et al.
    Radboud University, Netherlands.
    Mitra, P.
    Vrije Universiteit, Belgium.
    Bonardi, A.
    Radboud University, Netherlands.
    Buitink, S.
    Vrije Universiteit, Belgium.
    Falcke, H.
    Radboud University, Netherlands;NIKHEF, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Hare, B. M.
    University Groningen, Netherlands.
    Hörandel, J. R.
    Radboud University, Netherlands;NIKHEF, Netherlands.
    Mulrey, K.
    Vrije Universiteit, Belgium.
    Nelles, A.
    Radboud University, Netherlands;University of California, USA.
    Rachen, J. P.
    Radboud University, Netherlands.
    Rossetto, L.
    Radboud University, Netherlands.
    Schellart, P.
    Radboud University, Netherlands;Princeton University, USA.
    Scholten, O.
    University Groningen, Netherlands.
    Ter Veen, S.
    Radboud University, Netherlands;Netherlands Institute of Radio Astronomy (ASTRON), Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud University, Netherlands.
    Trinh, T. N. G.
    University Groningen, 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).

  • 17. Corstanje, A.
    et al.
    Schellart, P.
    Nelles, A.
    Buitink, S.
    Enriquez, J. E.
    Falcke, H.
    Frieswijk, W.
    Hörandel, J. R.
    Krause, M.
    Rachen, J. P.
    Scholten, O.
    ter Veen, S.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Trinh, T. N. G.
    van den Akker, M.
    Alexov, A.
    Anderson, J.
    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.
    de Gasperin, F.
    de Geus, E.
    de Vos, M.
    Duscha, S.
    Eislöffel, J.
    Engels, D.
    Fallows, R. A.
    Ferrari, C.
    Garrett, M. A.
    Grießmeier, J.
    Gunst, A. W.
    Hamaker, J. P.
    Hoeft, M.
    Horneffer, A.
    Iacobelli, M.
    Juette, E.
    Karastergiou, A.
    Kohler, J.
    Kondratiev, V. I.
    Kuniyoshi, M.
    Kuper, G.
    Maat, P.
    Mann, G.
    McFadden, R.
    McKay-Bukowski, D.
    Mevius, M.
    Munk, H.
    Norden, M. J.
    Orru, E.
    Paas, H.
    Pandey-Pommier, M.
    Pandey, V. N.
    Pizzo, R.
    Polatidis, A. G.
    Reich, W.
    Röttgering, H.
    Scaife, A. M. M.
    Schwarz, D.
    Smirnov, O.
    Stewart, A.
    Steinmetz, M.
    Swinbank, J.
    Tagger, M.
    Tang, Y.
    Tasse, C.
    Toribio, C.
    Vermeulen, R.
    Vocks, C.
    van Weeren, R. J.
    Wijnholds, S. J.
    Wucknitz, O.
    Yatawatta, S.
    Zarka, P.
    The shape of the radio wavefront of extensive air showers as measured with LOFAR2015In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 61, p. 22-31Article in journal (Refereed)
    Abstract [en]

    Extensive air showers, induced by high energy cosmic rays impinging on the Earth’s atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or hyperbolic shape of the wavefront has been proposed, but measurements of individual air showers have been inconclusive so far. For a selected high-quality sample of 161 measured extensive air showers, we have reconstructed the wavefront by measuring pulse arrival times to sub-nanosecond precision in 200 to 350 individual antennas. For each measured air shower, we have fitted a conical, spherical, and hyperboloid shape to the arrival times. The fit quality and a likelihood analysis show that a hyperboloid is the best parameterization. Using a non-planar wavefront shape gives an improved angular resolution, when reconstructing the shower arrival direction. Furthermore, a dependence of the wavefront shape on the shower geometry can be seen. This suggests that it will be possible to use a wavefront shape analysis to get an additional handle on the atmospheric depth of the shower maximum, which is sensitive to the mass of the primary particle.

  • 18.
    Corstanje, A.
    et al.
    Radboud University Nijmegen, The Netherlands.
    van den Akker, M.
    Radboud University Nijmegen, The Netherlands.
    Bähren, L.
    Radboud University Nijmegen, The Netherlands.
    Falcke, H.
    Radboud University Nijmegen, The Netherlands ; Kernfysisch Versneller Instituut, The Netherlands.
    Frieswijk, W.
    Kernfysisch Versneller Instituut, The Netherlands.
    Hörandel, J. R.
    Radboud University Nijmegen, The Netherlands.
    Horneffer, A.
    Radboud University Nijmegen, The Netherlands.
    James, C. W.
    Radboud University Nijmegen, The Netherlands.
    Kelley, J. L.
    Radboud University Nijmegen, The Netherlands.
    McFadden, R.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Mevius, M.
    Kernfysisch Versneller Instituut, The Netherlands.
    Nelles, A.
    Radboud University Nijmegen, The Netherlands.
    Schellart, P.
    Radboud University Nijmegen, The Netherlands.
    Scholten, O.
    Kernfysisch Versneller Instituut, The Netherlands.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    ter Veen, S.
    Radboud University Nijmegen, The Netherlands.
    LOFAR: Detecting Cosmic Rays with a Radio Telescope2011In: Proceedings of the 32nd International Cosmic Ray Conference: Aug. 11-18, 2011. Beijing, China, International Union of Pure and Applied Physics (IUPAP) , 2011, Vol. 3, p. 192-195Conference paper (Other academic)
    Abstract [en]

    LOFAR (the Low Frequency Array), a distributed digital radio telescope with stations in the Netherlands, Germany, France, Sweden, and the United Kingdom, is designed to enable full-sky monitoring of transient radio sources. These capabilities are ideal for the detection of broadband radio pulses generated in cosmic ray air showers. The core of LOFAR consists of 24 stations within 4 square kilometers, and each station contains 96 low-band antennas and 48 high-band antennas. This dense instrumentation will allow detailed studies of the lateral distribution of the radio signal in a frequency range of 10-250 MHz. Such studies are key to understanding the various radio emission mechanisms within the air shower, as well as for determining the potential of the radio technique for primary particle identification. We present the status of the LOFAR cosmic ray program, including the station design and hardware, the triggering and filtering schemes, and our initial observations of cosmic-ray-induced radio pulses.

  • 19.
    Dhar, V. K.
    et al.
    Bhabha Atomic Research Centre, India.
    Koul, M. K.
    Bhabha Atomic Research Centre, India.
    Tickoo, A. K.
    Bhabha Atomic Research Centre, India.
    Yadav, K. K.
    Bhabha Atomic Research Centre, India.
    Thoudam, Satyendra
    Bhabha Atomic Research Centre, India.
    Dubey, B. P.
    Bhabha Atomic Research Centre, India.
    Venugopal, K.
    Bhabha Atomic Research Centre, India.
    Bhatt, N.
    Bhabha Atomic Research Centre, India.
    Bhattacharyya, S.
    Bhabha Atomic Research Centre, India.
    Chandra, P.
    Bhabha Atomic Research Centre, India.
    Goyal, H. C.
    Bhabha Atomic Research Centre, India.
    Kaul, R. K.
    Bhabha Atomic Research Centre, India.
    Kothari, M.
    Bhabha Atomic Research Centre, India.
    Kotwal, S.
    Bhabha Atomic Research Centre, India.
    Koul, R.
    Bhabha Atomic Research Centre, India.
    Rannot, R. C.
    Bhabha Atomic Research Centre, India.
    Sahyanathan, S.
    Bhabha Atomic Research Centre, India.
    Sharma, M.
    Bhabha Atomic Research Centre, India.
    ANN based energy estimation procedure and energy spectrum of the Crab Nebula as measured by the TACTIC gamma-ray telescope2005In: 29th International Cosmic Ray Conference Pune (2005), 2005, Vol. 4, p. 179-182Conference paper (Refereed)
    Abstract [en]

    A novel energy reconstruction procedure based on the utilization of Articial Neural Network has been developedfor the TACTIC atmospheric Cerenkov imaging telescope to estimate the energy of the primary gammaraysin the TeV energy range. The procedure uses a 3:20:1 conguration of the ANN with resilient backpropagationtraining algorithm to estimate the energy of a-ray like event on the basis of its image SIZE,DISTANCE and zenith angle. The results obtained by using the CORSIKA code simulated data suggest theenergy resolution of the telescope is40for retaining90of the-ray events in a particular energybin which is comparable to the energy resolution of other single element imaging telescopes. Details of theenergy estimation procedure along with results obtained by determining the Crab Nebula energy spectrum inthe energy range 1-16 TeV as measured by the TACTIC telescope are presented in the paper.

  • 20. Ebert, U.
    et al.
    Trinh, G. T. N.
    Buitink, S.
    Corstanje, A.
    Enriquez, J. E.
    Falcke, H.
    Horandel, J.
    Koehn, C.
    Nelles, A.
    Rachen, J. P.
    Rutjes, C.
    Schellart, P.
    Scholten, O.
    ter Veen, S.
    Thoudam, Satyendra
    Determining atmospheric electric fields from the radio footprint of cosmic-ray induced extensive air showers as measured with LOFAR2014In: AGU Fall Meeting Abstracts 2014, 2014Conference paper (Refereed)
  • 21.
    Garsden, H.
    et al.
    Université Paris Diderot, France.
    Girard, J. N.
    Université Paris Diderot, France.
    Starck, J. L.
    Université Paris Diderot, France.
    Corbel, S.
    Université Paris Diderot, France.
    Tasse, C.
    Rhodes University, South Africa ; SKA South Africa, South Africa.
    Woiselle, A.
    Sagem (Safran), France ; Université Paris Diderot, France.
    McKean, J. P.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    van Amesfoort, A. S.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Anderson, J.
    Helmholtz-Zentrum Potsdam, Germany ; Leibniz-Institut für Astrophysik Potsdam (AIP), Germany.
    Avruch, I. M.
    SRON Netherlands Institute for Space Research, The Netherlands ; Kapteyn Astronomical Institute, The Netherlands .
    Beck, R.
    Max-Planck-Institut für Radioastronomie, Germany .
    Bentum, M. J.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands ; University of Twente, Germany .
    Best, P.
    University of Edinburgh, UK.
    Breitling, F.
    Leibniz-Institut für Astrophysik Potsdam (AIP), Germany.
    Broderick, J.
    University of Southampton, UK.
    Brüggen, M.
    University of Hamburg, Germany.
    Butcher, H. R.
    Australian National University, Australia .
    Ciardi, B.
    Max Planck Institute for Astrophysics, Germany.
    de Gasperin, F.
    University of Hamburg, Germany.
    de Geus, E.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands ; SmarterVision BV, The Netherlands .
    de Vos, M.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Duscha, S.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Eislöffel, J.
    Thüringer Landessternwarte, Germany.
    Engels, D.
    Hamburger Sternwarte, Germany.
    Falcke, H.
    Department of Astrophysics/IMAPP, The Netherlands ; Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Fallows, R. A.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Fender, R.
    University of Oxford, UK.
    Ferrari, C.
    Université de Nice Sophia-Antipolis, France.
    Frieswijk, W.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Garrett, M. A.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands ; Leiden University, The Netherlands .
    Grießmeier, J.
    Universite d’Orléans/CNRS, France ; Observatoire de Paris – CNRS/INSU, France.
    Gunst, A. W.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Hassall, T. E.
    University of Southampton, UK ; The University of Manchester, UK.
    Heald, G.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Hoeft, M.
    Thüringer Landessternwarte, Germany.
    Hörandel, J.
    Radboud University Nijmegen, The Netherlands .
    van der Horst, A.
    University of Amsterdam, The Netherlands.
    Juette, E.
    Astronomisches Institut der Ruhr-Universität Bochum, Germany.
    Karastergiou, A.
    University of Oxford, UK.
    Kondratiev, V. I.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands ; Astro Space Center of the Lebedev Physical Institute, Russia .
    Kramer, M.
    Max-Planck-Institut für Radioastronomie, Germany ; The University of Manchester, UK.
    Kuniyoshi, M.
    Max-Planck-Institut für Radioastronomie, Germany.
    Kuper, G.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Mann, G.
    Leibniz-Institut für Astrophysik Potsdam (AIP), Germany .
    Markoff, S.
    University of Amsterdam, The Netherlands.
    McFadden, R.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    McKay-Bukowski, D.
    University of Oulu, Finland ; University of Groningen, he Netherlands .
    Mulcahy, D. D.
    Max-Planck-Institut für Radioastronomie, Germany.
    Munk, H.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Norden, M. J.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Orru, E.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Paas, H.
    University of Groningen, The Netherlands .
    Pandey-Pommier, M.
    Observatoire de Lyon, France.
    Pandey, V. N.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Pietka, G.
    University of Oxford, UK.
    Pizzo, R.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Polatidis, A. G.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Renting, A.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Röttgering, H.
    Leiden University, The Netherlands.
    Rowlinson, A.
    University of Amsterdam, The Netherlands .
    Schwarz, D.
    Universität Bielefeld, Germany .
    Sluman, J.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Smirnov, O.
    Rhodes University, South Africa ; SKA South Africa, South Africa.
    Stappers, B. W.
    The University of Manchester, UK.
    Steinmetz, M.
    Leibniz-Institut für Astrophysik Potsdam (AIP), Germany.
    Stewart, A.
    University of Oxford, UK.
    Swinbank, J.
    University of Amsterdam, The Netherlands .
    Tagger, M.
    LPC2E – Universite d’Orléans/CNRS, France.
    Tang, Y.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands .
    Toribio, C.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands.
    Vermeulen, R.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Vocks, C.
    Leibniz-Institut für Astrophysik Potsdam (AIP), Germany.
    van Weeren, R. J.
    Harvard-Smithsonian Center for Astrophysics, USA.
    Wijnholds, S. J.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Wise, M. W.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands ; University of Amsterdam, The Netherlands .
    Wucknitz, O.
    Max-Planck-Institut für Radioastronomie, Germany.
    Yatawatta, S.
    Netherlands Institute for Radio Astronomy (ASTRON), The Netherlands .
    Zarka, P.
    Observatoire de Paris, France.
    Zensus, A.
    Max-Planck-Institut für Radioastronomie, Germany .
    LOFAR sparse image reconstruction2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 575, no A90Article in journal (Refereed)
    Abstract [en]

    Context. The LOw Frequency ARray (LOFAR) radio telescope is a giant digital phased array interferometer with multiple antennas distributed in Europe. It provides discrete sets of Fourier components of the sky brightness. Recovering the original brightness distribution with aperture synthesis forms an inverse problem that can be solved by various deconvolution and minimization methods.

    Aims. Recent papers have established a clear link between the discrete nature of radio interferometry measurement and the “compressed sensing” (CS) theory, which supports sparse reconstruction methods to form an image from the measured visibilities. Empowered by proximal theory, CS offers a sound framework for efficient global minimization and sparse data representation using fast algorithms. Combined with instrumental direction-dependent effects (DDE) in the scope of a real instrument, we developed and validated a new method based on this framework.

    Methods. We implemented a sparse reconstruction method in the standard LOFAR imaging tool and compared the photometric and resolution performance of this new imager with that of CLEAN-based methods (CLEAN and MS-CLEAN) with simulated and real LOFAR data.

    Results. We show that i) sparse reconstruction performs as well as CLEAN in recovering the flux of point sources; ii) performs much better on extended objects (the root mean square error is reduced by a factor of up to 10); and iii) provides a solution with an effective angular resolution 2−3 times better than the CLEAN images.

    Conclusions. Sparse recovery gives a correct photometry on high dynamic and wide-field images and improved realistic structures of extended sources (of simulated and real LOFAR datasets). This sparse reconstruction method is compatible with modern interferometric imagers that handle DDE corrections (A- and W-projections) required for current and future instruments such as LOFAR and SKA.

  • 22.
    Girard, J. N.
    et al.
    Rhodes University, South Africa ; SKA South Africa, South Africa ; CEA Saclay, France.
    Zarka, P.
    Paris Observatory, France.
    Tasse, C.
    Paris Observatory, France.
    Hess, S.
    ONERA, France.
    de Pater, I.
    University of California, USA.
    Santos-Costa, D.
    Southwest Research Institute, USA.
    Nenon, Q.
    ONERA, France.
    Sicard, A.
    ONERA, France.
    Bourdarie, S.
    ONERA, France.
    Anderson, J.
    Hlmholtz Centre Potsdam, Germany.
    Asgekar, A.
    Bell, M. E.
    van Bemmel, I.
    Bentum, M. J.
    Bernardi, G.
    Best, P.
    Bonafede, A.
    Breitling, F.
    Breton, R. P.
    Broderick, J. W.
    Brouw, W. N.
    Brüggen, M.
    Ciardi, B.
    Corbel, S.
    Corstanje, A.
    de Gasperin, F.
    de Geus, E.
    Deller, A.
    Duscha, S.
    Eislöffel, J.
    Falcke, H.
    Frieswijk, W.
    Garrett, M. A.
    Grießmeier, J.
    Gunst, A. W.
    Hessels, J. W. T.
    Hoeft, M.
    Hörandel, J.
    Iacobelli, M.
    Juette, E.
    Kondratiev, V. I.
    Kuniyoshi, M.
    Kuper, G.
    van Leeuwen, J.
    Loose, M.
    Maat, P.
    Mann, G.
    Markoff, S.
    McFadden, R.
    McKay-Bukowski, D.
    Moldon, J.
    Munk, H.
    Nelles, A.
    Norden, M. J.
    Orru, E.
    Paas, H.
    Pandey-Pommier, M.
    Pizzo, R.
    Polatidis, A. G.
    Reich, W.
    Röttgering, H.
    Rowlinson, A.
    Schwarz, D.
    Smirnov, O.
    Steinmetz, M.
    Swinbank, J.
    Tagger, M.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Toribio, M. C.
    Vermeulen, R.
    Vocks, C.
    van Weeren, R. J.
    Wijers, R. A. M. J.
    Wucknitz, O.
    Imaging Jupiter’s radiation belts down to 127 MHz with LOFAR2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 587, article id A3Article in journal (Refereed)
    Abstract [en]

    Context. With the limited amount of in situ particle data available for the innermost region of Jupiter’s magnetosphere, Earth-based observations of the giant planets synchrotron emission remain the sole method today of scrutinizing the distribution and dynamical behavior of the ultra energetic electrons magnetically trapped around the planet. Radio observations ultimately provide key information about the origin and control parameters of the harsh radiation environment.

    Aims. We perform the first resolved and low-frequency imaging of the synchrotron emission with LOFAR. At a frequency as low as 127 MHz, the radiation from electrons with energies of ~1–30 MeV are expected, for the first time, to be measured and mapped over a broad region of Jupiter’s inner magnetosphere.

    Methods. Measurements consist of interferometric visibilities taken during a single 10-hour rotation of the Jovian system. These visibilities were processed in a custom pipeline developed for planetary observations, combining flagging, calibration, wide-field imaging, direction-dependent calibration, and specific visibility correction for planetary targets. We produced spectral image cubes of Jupiter’s radiation belts at the various angular, temporal, and spectral resolutions from which flux densities were measured.

    Results. The first resolved images of Jupiter’s radiation belts at 127–172 MHz are obtained with a noise level ~20–25 mJy/beam, along with total integrated flux densities. They are compared with previous observations at higher frequencies. A greater extent of the synchrotron emission source (≥4 RJ) is measured in the LOFAR range, which is the signature – as at higher frequencies – of the superposition of a “pancake” and an isotropic electron distribution. Asymmetry of east-west emission peaks is measured, as well as the longitudinal dependence of the radial distance of the belts, and the presence of a hot spot at λIII = 230° ± 25°. Spectral flux density measurements are on the low side of previous (unresolved) ones, suggesting a low-frequency turnover and/or time variations of the Jovian synchrotron spectrum.

    Conclusions. LOFAR proves to be a powerful and flexible planetary imager. In the case of Jupiter, observations at 127 MHz depict the distribution of ~1–30 MeV energy electrons up to ~4–5 planetary radii. The similarities of the observations at 127 MHz with those at higher frequencies reinforce the conclusion that the magnetic field morphology primarily shapes the brightness distribution features of Jupiter’s synchrotron emission, as well as how the radiating electrons are likely radially and latitudinally distributed inside about 2 planetary radii. Nonetheless, the detection of an emission region that extends to larger distances than at higher frequencies, combined with the overall lower flux density, yields new information on Jupiter’s electron distribution, and this information may ultimately shed light on the origin and mode of transport of these particles.

  • 23.
    Godambe, S. V.
    et al.
    Bhabha Atomic Research Centre, India.
    Rannot, R. C.
    Bhabha Atomic Research Centre, India.
    Baliyan, K. S.
    Physical Research Laboratory, India.
    Tickoo, A. K.
    Bhabha Atomic Research Centre, India.
    Thoudam, Satyendra
    Bhabha Atomic Research Centre, India.
    Dhar, V. K.
    Bhabha Atomic Research Centre, India.
    Chandra, P.
    Bhabha Atomic Research Centre, India.
    Yadav, K. K.
    Bhabha Atomic Research Centre, India.
    Venugopal, K.
    Bhabha Atomic Research Centre, India.
    Bhatt, N.
    Bhabha Atomic Research Centre, India.
    Bhattacharyya, S.
    Bhabha Atomic Research Centre, India.
    Chanchalani, K.
    Bhabha Atomic Research Centre, India.
    Ganesh, S.
    Physical Research Laboratory, India.
    Goyal, H. C.
    Bhabha Atomic Research Centre, India.
    Joshi, U. C.
    Physical Research Laboratory, India.
    Kaul, R. K.
    Bhabha Atomic Research Centre, India.
    Kothari, M.
    Bhabha Atomic Research Centre, India.
    Kotwal, S.
    Bhabha Atomic Research Centre, India.
    Koul, M. K.
    Bhabha Atomic Research Centre, India.
    Koul, R.
    Bhabha Atomic Research Centre, India.
    Sahaynathan, S.
    Bhabha Atomic Research Centre, India.
    Shah, C.
    Physical Research Laboratory, India.
    Sharma, M.
    Bhabha Atomic Research Centre, India.
    Very high energy γ-ray and near infrared observations of 1ES2344+514 during 2004 052007In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 34, p. 1683-1695Article in journal (Refereed)
    Abstract [en]

    We have observed the BL Lac object 1ES2344+514 (z = 0.044) in very high energy (VHE) gamma-ray and near-infrared wavelength bands with TACTIC and MIRO telescopes, respectively. The observations were made from 18th October to 9th December 2004 and 27th October 2005 to 1st January 2006. Detailed analysis of the TACTIC data indicates the absence of a statistically significant gamma-ray signal both in overall data and on a nightly basis from the source direction. We estimate an upper limit of I(≥1.5 TeV) ≤ 3.84 × 10−12 photons cm−2 s−1 at a 3σ confidence level on the integrated γ-ray flux. In addition, we have also compared TACTIC TeV light curves with those of the RXTE ASM (2–12 keV) for the contemporary period and find that there are no statistically significant increases in the signal strengths from the source in both these energy regions. During 2004 IR observations, 1ES2344+514 shows low level (0.06 magnitude) day-to-day variation in both, J and H bands. However, during the 2005 observation epoch, the source brightens up by about 0.41 magnitude from its October 2005 level J magnitude = 12.64 to J = 12.23 on December 6, 2005. It then fades by about 0.2 magnitude during 6 to 10 December, 2005. The variation is seen in both, J and H, bands simultaneously. The light travel time arguments suggest that the emission region size is of the order of 1017 cm.

  • 24.
    Godambe, S. V.
    et al.
    Bhabha Atomic Research Centre, India.
    Rannot, R. C.
    Bhabha Atomic Research Centre, India.
    Chandra, P.
    Bhabha Atomic Research Centre, India.
    Yadav, K. K.
    Bhabha Atomic Research Centre, India.
    Tickoo, A. K.
    Bhabha Atomic Research Centre, India.
    Venugopal, K.
    Bhabha Atomic Research Centre, India.
    Bhatt, N.
    Bhabha Atomic Research Centre, India.
    Bhattacharyya, S.
    Bhabha Atomic Research Centre, India.
    Chanchalani, K.
    Bhabha Atomic Research Centre, India.
    Dhar, V. K.
    Bhabha Atomic Research Centre, India.
    Goyal, H. C.
    Bhabha Atomic Research Centre, India.
    Kaul, R. K.
    Bhabha Atomic Research Centre, India.
    Kothari, M.
    Bhabha Atomic Research Centre, India.
    Kotwal, S.
    Bhabha Atomic Research Centre, India.
    Koul, M. K.
    Bhabha Atomic Research Centre, India.
    Koul, R.
    Bhabha Atomic Research Centre, India.
    Sahaynathan, B. S.
    Bhabha Atomic Research Centre, India.
    Sharma, M.
    Bhabha Atomic Research Centre, India.
    Thoudam, Satyendra
    Bhabha Atomic Research Centre, India.
    Very high energy γ-ray observations of Mrk 501 using the TACTIC imaging γ-ray telescope during 2005 062008In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 35, no 6, article id 065202Article in journal (Refereed)
    Abstract [en]

    In this paper we report on the Markarian 501 results obtained during our TeV γ-ray observations from 11 March to 12 May 2005 and 28 February to 7 May 2006 for 112.5 h with the TACTIC γ-ray telescope. During 2005 observations for 45.7 h, the source was found to be in a low state and we have placed an upper limit of 4.62 × 10−12 photons cm−2 s−1 at 3σ level on the integrated TeV γ-ray flux above 1 TeV from the source direction. However, during 2006 observations for 66.8 h, detailed data analysis revealed the presence of a TeV γ-ray signal from the source with a statistical significance of 7.5σ above Eγ≥ 1 TeV. The time-averaged differential energy spectrum of the source in the energy range 1–11 TeV is found to match well with the power-law function of the form (dΦ/dE = f0E−Γ) with f0 = (1.66 ± 0.52) × 10−11 cm−2 s−1 TeV−1 and Γ = 2.80 ± 0.27.

  • 25.
    Godambe, S. V.
    et al.
    Bhabha Atomic Research Centre, India.
    Thoudam, Satyendra
    Bhabha Atomic Research Centre, India.
    Rannot, R. C.
    Bhabha Atomic Research Centre, India.
    Chandra, P.
    Bhabha Atomic Research Centre, India.
    Sahayanathan, S.
    Bhabha Atomic Research Centre, India.
    Sharma, M.
    Physical Research Laboratory, India.
    Venugopal, K.
    Bhabha Atomic Research Centre, India.
    Bhatt, N.
    Bhabha Atomic Research Centre, India.
    Bhattacharyya, S.
    Bhabha Atomic Research Centre, India.
    Dhar, V. K.
    Bhabha Atomic Research Centre, India.
    Goyal, H. C.
    Bhabha Atomic Research Centre, India.
    Kaul, R. K.
    Bhabha Atomic Research Centre, India.
    Kothari, M.
    Bhabha Atomic Research Centre, India.
    Kotwal, S.
    Bhabha Atomic Research Centre, India.
    Koul, R.
    Bhabha Atomic Research Centre, India.
    Yadav, K. K.
    Bhabha Atomic Research Centre, India.
    Tickoo, A. K.
    Bhabha Atomic Research Centre, India.
    Baliyan, K. S.
    Physical Research Laboratory, India.
    Joshi, U. C.
    Physical Research Laboratory, India.
    Ganesh, S.
    Physical Research Laboratory, India.
    Shah, C.
    Physical Research Laboratory, India.
    Ohlan, A.
    Physical Research Laboratory, India.
    Very High Energy Gamma-ray and Near Infrared observations of 1ES2344+514 with TACTIC and MIRO Telescopes2005In: 29th International Cosmic Ray Conference Pune (2005), 2005, Vol. 4Conference paper (Refereed)
    Abstract [en]

    1ES2344+514 (z = 0.04) is one of the rst BL Lac objects to be reported as an extreme synchrotron blazar withsynchotron peak energy reaching up to 100keV and was discovered as a source of Very High Energy (VHE)gamma- rays by the Whipple group in 1995. Subsequently, it was observed by the HEGRA group in 1997/98and 2002. We have recently (Oct.- Dec. 2004) observed the 1ES2344+514 using the imaging element of theTACTIC array and have collected data for 53 hours in on/off mode. The source was also observed in nearinfrared bands J, H and K, for some nights using NICMOS-3 array mounted on 1.2m MIRO infrared telescope.Such a study is expected to provide clues to the dominance or otherwise of the Compton component. Afterdetailed analysis of the TACTIC data we have placed an upper limit of    photons cmsata 3condence level on the gamma-ray ux from the source. In the near infrared band the source shows lowlevel variations without any aring activity.

  • 26.
    Hare, B. M.
    et al.
    Univ Groningen, Netherlands.
    Scholten, O.
    Univ Groningen, Netherlands;Vrije Univ Brussel, Belgium.
    Bonardi, A.
    Radboud Univ Nijmegen, Netherlands.
    Buitink, S.
    Vrije Univ Brussel, Belgium.
    Corstanje, A.
    Radboud Univ Nijmegen, Netherlands.
    Ebert, U.
    Ctr Math & Comp Sci, Netherlands;Eindhoven Univ Technol, Netherlands.
    Falcke, H.
    Vrije Univ Brussel, Belgium;NIKHEF, Netherlands;Netherlands Inst Radio Astron ASTRON, Netherlands;Max Planck Inst Radioastron, Germany.
    Horandel, J. R.
    Radboud Univ Nijmegen, Netherlands;NIKHEF, Netherlands.
    Leijnse, H.
    Royal Netherlands Meteorol Inst, Netherlands.
    Mitra, P.
    Vrije Univ Brussel, Belgium.
    Mulrey, K.
    Vrije Univ Brussel, Belgium.
    Nelles, A.
    Radboud Univ Nijmegen, Netherlands;Univ Calif Irvine, USA.
    Rachen, J. P.
    Radboud Univ Nijmegen, Netherlands.
    Rossetto, L.
    Radboud Univ Nijmegen, Netherlands.
    Rutjes, C.
    Ctr Math & Comp Sci, Netherlands.
    Schellart, P.
    Radboud Univ Nijmegen, Netherlands;Princeton Univ, USA.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Trinh, T. N. G.
    Univ Groningen, Netherlands.
    ter Veen, S.
    Radboud Univ Nijmegen, Netherlands;Netherlands Inst Radio Astron ASTRON, Netherlands.
    Winchen, T.
    Vrije Univ Brussel, Belgium.
    LOFAR Lightning Imaging: Mapping Lightning With Nanosecond Precision2018In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 123, no 5, p. 2861-2876Article in journal (Refereed)
    Abstract [en]

    Lightning mapping technology has proven instrumental in understanding lightning. In this work we present a pipeline that can use lightning observed by the LOw-Frequency ARray (LOFAR) radio telescope to construct a 3-D map of the flash. We show that LOFAR has unparalleled precision, on the order of meters, even for lightning flashes that are over 20km outside the area enclosed by LOFAR antennas (approximate to 3,200km(2)), and can potentially locate over 10,000 sources per lightning flash. We also show that LOFAR is the first lightning mapping system that is sensitive to the spatial structure of the electrical current during individual lightning leader steps.

  • 27. Heald, G. H.
    et al.
    Pizzo, R. F.
    Orrú, E.
    Breton, R. P.
    Carbone, D.
    Ferrari, C.
    Hardcastle, M. J.
    Jurusik, W.
    Macario, G.
    Mulcahy, D.
    Rafferty, D.
    Asgekar, A.
    Brentjens, M.
    Fallows, R. A.
    Frieswijk, W.
    Toribio, M. C.
    Adebahr, B.
    Arts, M.
    Bell, M. R.
    Bonafede, A.
    Bray, J.
    Broderick, J.
    Cantwell, T.
    Carroll, P.
    Cendes, Y.
    Clarke, A. O.
    Croston, J.
    Daiboo, S.
    de Gasperin, F.
    Gregson, J.
    Harwood, J.
    Hassall, T.
    Heesen, V.
    Horneffer, A.
    van der Horst, A. J.
    Iacobelli, M.
    Jelić, V.
    Jones, D.
    Kant, D.
    Kokotanekov, G.
    Martin, P.
    McKean, J. P.
    Morabito, L. K.
    Nikiel-Wroczy´nski, B.
    Offringa, A.
    Pandey, V. N.
    Pandey-Pommier, M.
    Pietka, M.
    Pratley, L.
    Riseley, C.
    Rowlinson, A.
    Sabater, J.
    Scaife, A. M. M.
    Scheers, L. H. A.
    Sendlinger, K.
    Shulevski, A.
    Sipior, M.
    Sobey, C.
    Stewart, A. J.
    Stroe, A.
    Swinbank, J.
    Tasse, C.
    Trüstedt, J.
    Varenius, E.
    van Velzen, S.
    Vilchez, N.
    van Weeren, R. J.
    Wijnholds, S.
    Williams, W. L.
    de Bruyn, A. G.
    Nijboer, R.
    Wise, M.
    Alexov, A.
    Anderson, J.
    Avruch, I. M.
    Beck, R.
    Bell, M. E.
    van Bemmel, I.
    Bentum, M. J.
    Bernardi, G.
    Best, P.
    Breitling, F.
    Brouw, W. N.
    Brüggen, M.
    Butcher, H. R.
    Ciardi, B.
    Conway, J. E.
    de Geus, E.
    de Jong, A.
    de Vos, M.
    Deller, A.
    Dettmar, R. -J
    Duscha, S.
    Eislöffel, J.
    Engels, D.
    Falcke, H.
    Fender, R.
    Garrett, M. A.
    Grießmeier, J.
    Gunst, A. W.
    Hamaker, J. P.
    Hessels, J. W. T.
    Hoeft, M.
    Hörandel, J.
    Holties, H. A.
    Intema, H.
    Jackson, N. J.
    Jütte, E.
    Karastergiou, A.
    Klijn, W. F. A.
    Kondratiev, V. I.
    Koopmans, L. V. E.
    Kuniyoshi, M.
    Kuper, G.
    Law, C.
    van Leeuwen, J.
    Loose, M.
    Maat, P.
    Markoff, S.
    McFadden, R.
    McKay-Bukowski, D.
    Mevius, M.
    Miller-Jones, J. C. A.
    Morganti, R.
    Munk, H.
    Nelles, A.
    Noordam, J. E.
    Norden, M. J.
    Paas, H.
    Polatidis, A. G.
    Reich, W.
    Renting, A.
    Röttgering, H.
    Schoenmakers, A.
    Schwarz, D.
    Sluman, J.
    Smirnov, O.
    Stappers, B. W.
    Steinmetz, M.
    Tagger, M.
    Tang, Y.
    ter Veen, S.
    Thoudam, Satyendra
    Radboud University, The Netherlands.
    Vermeulen, R.
    Vocks, C.
    Vogt, C.
    Wijers, R. A. M. J.
    Wucknitz, O.
    Yatawatta, S.
    Zarka, P.
    The LOFAR Multifrequency Snapshot Sky Survey (MSSS): I. Survey description and first results2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 582, p. 1-22, article id A123Article in journal (Refereed)
    Abstract [en]

    We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky Low Frequency Array (LOFAR) imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR’s multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the MSSS Verification Field (MVF), a region of 100 square degrees centered at (α,δ)J2000 = (15h,69°). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108″ resolution, and 550 mJy at 50 MHz with 166″ resolution. Images and catalogs for the full survey, expected to contain 150 000–200 000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs.

  • 28.
    Horandel, Jorg R.
    et al.
    Radboud Univ Nijmegen, Netherlands ; NIKHEF, Netherlands.
    Bonardi, A.
    Radboud Univ Nijmegen, Netherlands.
    Buitink, S.
    Radboud Univ Nijmegen, Netherlands ; Vrije Univ Brussel, Belgium.
    Corstanje, A.
    Radboud Univ Nijmegen, Netherlands.
    Falcke, H.
    Radboud Univ Nijmegen, Netherlands ; NIKHEF, Netherlands ; Max Planck Inst Radio Astron, Germany.
    Mitra, P.
    Vrije Univ Brussel, Belgium.
    Mulrey, K.
    Vrije Univ Brussel, Belgium.
    Nelles, A.
    Radboud Univ Nijmegen, Netherlands ; NIKHEF, Netherlands ; Univ Calif Irvine, USA.
    Rachen, J. P.
    Radboud Univ Nijmegen, Netherlands.
    Rossetto, L.
    Radboud Univ Nijmegen, Netherlands.
    Schellart, P.
    Radboud Univ Nijmegen, Netherlands ; Princeton Univ, USA.
    Scholten, O.
    Univ Groningen, Netherlands ; Vrije Univ Brussel, Belgium.
    ter Veen, S.
    ASTRON, Netherlands.
    Thoudam, Satyendra
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering. Radboud Univ Nijmegen, Netherlands.
    Trinh, T. N. G.
    Univ Groningen, Netherlands.
    Winchen, T.
    Vrije Univ Brussel, Belgium.
    The mass composition of cosmic rays measured with LOFAR2017In: RICAP16, 6TH ROMA INTERNATIONAL CONFERENCE ON ASTROPARTICLE PHYSICS / [ed] Morselli, A Capone, A Fernandez, GR, 2017, article id UNSP 02001Conference paper (Refereed)
    Abstract [en]

    High-energy cosmic rays, impinging on the atmosphere of the Earth initiate cascades of secondary particles, the extensive air showers. The electrons and positrons in the air shower emit electromagnetic radiation. This emission is detected with the LOFAR radio telescope in the frequency range from 30 to 240 MHz. The data are used to determine the properties of the incoming cosmic rays. The radio technique is now routinely used to measure the arrival direction, the energy, and the particle type (atomic mass) of cosmic rays in the energy range from 10(17) to 10(18) eV. This energy region is of particular astrophysical interest, since in this regime a transition from a Galactic to an extra-galactic origin of cosmic rays is expected. For illustration, the LOFAR results are used to set constraints on models to describe the origin of high-energy cosmic rays.

  • 29.
    Horneffer, A.
    et al.
    Radboud University Nijmegen, The Netherlands.
    Bähren, L.
    Radboud University Nijmegen, The Netherlands.
    Buitink, S.
    Radboud University Nijmegen, The Netherlands.
    Corstanje, A.
    Radboud University Nijmegen, The Netherlands.
    Falcke, H.
    Radboud University Nijmegen, The Netherlands ; ASTRON, The Netherlands.
    Hörandel, J. R.
    Radboud University Nijmegen, The Netherlands.
    Lafebre, S.
    Radboud University Nijmegen, The Netherlands.
    Scholten, O.
    Kernfysisch Versneller Instituut, The Netherlands.
    Singh, K.
    Radboud University Nijmegen, The Netherlands ; Kernfysisch Versneller Instituut, The Netherlands.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Ter Veen, S.
    Radboud University Nijmegen, The Netherlands.
    Cosmic ray and neutrino measurements with LOFAR2010In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 617, no 1-3, p. 482-483Article in journal (Refereed)
    Abstract [en]

    LOFAR is a new radio telescope being built in the Netherlands. It can detect cosmic particles by measuring radio pulses from air showers and by searching for radio pulses from particle cascades in the moon. The high density of radio antennas in the core and the excellent calibration will make LOFAR an unique tool to study the radio properties of single air showers and thus test and refine our theoretical understanding of the radio emission process in them. In addition LOFAR will be able to observe the moon with high sensitivity at low frequencies and search for particles interacting in the lunar regolith. This will give it unprecedented sensitivity to cosmic rays or neutrinos at energies around 1022eV. Triggering for both detection methods means detecting a short radio pulse and discriminating real events from radio interference. At LOFAR we will search for pulses in the digital data stream either from single antennas or from already beam-formed data and pick out real events from pulse form data. In addition we will have a small scintillator array to test and confirm the performance of the radio only trigger, and to provide additional measurements for the air shower reconstruction and analysis.

  • 30. Jelić, V.
    et al.
    de Bruyn, A. G.
    Mevius, M.
    Abdalla, F. B.
    Asad, K. M. B.
    Bernardi, G.
    Brentjens, M. A.
    Bus, S.
    Chapman, E.
    Ciardi, B.
    Daiboo, S.
    Fernandez, E. R.
    Ghosh, A.
    Harker, G.
    Jensen, H.
    Kazemi, S.
    Koopmans, L. V. E.
    Labropoulos, P.
    Martinez-Rubi, O.
    Mellema, G.
    Offringa, A. R.
    Pandey, V. N.
    Patil, A. H.
    Thomas, R. M.
    Vedantham, H. K.
    Veligatla, V.
    Yatawatta, S.
    Zaroubi, S.
    Alexov, A.
    Anderson, J.
    Avruch, I. M.
    Beck, R.
    Bell, M. E.
    Bentum, M. J.
    Best, P.
    Bonafede, A.
    Bregman, J.
    Breitling, F.
    Broderick, J.
    Brouw, W. N.
    Brüggen, M.
    Butcher, H. R.
    Conway, J. E.
    de Gasperin, F.
    de Geus, E.
    Deller, A.
    Dettmar, R. -J
    Duscha, S.
    Eislöffel, J.
    Engels, D.
    Falcke, H.
    Fallows, R. A.
    Fender, R.
    Ferrari, C.
    Frieswijk, W.
    Garrett, M. A.
    Grießmeier, J.
    Gunst, A. W.
    Hamaker, J. P.
    Hassall, T. E.
    Haverkorn, M.
    Heald, G.
    Hessels, J. W. T.
    Hoeft, M.
    Hörandel, J.
    Horneffer, A.
    van der Horst, A.
    Iacobelli, M.
    Juette, E.
    Karastergiou, A.
    Kondratiev, V. I.
    Kramer, M.
    Kuniyoshi, M.
    Kuper, G.
    van Leeuwen, J.
    Maat, P.
    Mann, G.
    McKay-Bukowski, D.
    McKean, J. P.
    Munk, H.
    Nelles, A.
    Norden, M. J.
    Paas, H.
    Pandey-Pommier, M.
    Pietka, G.
    Pizzo, R.
    Polatidis, A. G.
    Reich, W.
    Röttgering, H.
    Rowlinson, A.
    Scaife, A. M. M.
    Schwarz, D.
    Serylak, M.
    Smirnov, O.
    Steinmetz, M.
    Stewart, A.
    Tagger, M.
    Tang, Y.
    Tasse, C.
    ter Veen, S.
    Thoudam, Satyendra
    Radboud University Nijmegen, The Netherlands.
    Toribio, C.
    Vermeulen, R.
    Vocks, C.
    van Weeren, R. J.
    Wijers, R. A. M. J.
    Wijnholds, S. J.
    Wucknitz, O.
    Zarka, P.
    Initial LOFAR observations of epoch of reionization windows: II. Diffuse polarized emission in the ELAIS-N1 field2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 568, p. 1-12, article id A101Article in journal (Refereed)
    Abstract [en]

    Aims. This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for extracting of the cosmological 21 cm signal from the LOw-Frequency ARray – Epoch of Reionization (LOFAR-EoR) data.

    Methods. We used the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes.

    Results. The brightness temperature of the detected Galactic emission is on average ~4 K in polarized intensity and covers the range from –10 to + 13 rad m-2 in Faraday depth. The total polarized intensity and polarization angle show a wide range of morphological features. We have also used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. The LOFAR and WSRT images show a similar complex morphology at comparable brightness levels, but their spatial correlation is very low. The fractional polarization at 150 MHz, expressed as a percentage of the total intensity, amounts to ≈1.5%. There is no indication of diffuse emission in total intensity in the interferometric data, in line with results at higher frequencies

    Conclusions. The wide frequency range, high angular resolution, and high sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of ~1–2 rad m-2 in Faraday depth. The different polarized patterns observed at 150 MHz and 350 MHz are consistent with different source distributions along the line of sight wring in a variety of Faraday thin regions of emission. The presence of polarized foregrounds is a serious complication for epoch of reionization experiments. To avoid the leakage of polarized emission into total intensity, which can depend on frequency, we need to calibrate the instrumental polarization across the field of view to a small fraction of 1%.

  • 31.
    Koul, R.
    et al.
    Bhabha Atomic Research Centre, India.
    Tickoo, A. K.
    Bhabha Atomic Research Centre, India.
    Kaul, S. K.
    Bhabha Atomic Research Centre, India.
    Kaul, S. R.
    Bhabha Atomic Research Centre, India.
    Kumar, N.
    Bhabha Atomic Research Centre, India.
    Yadav, K. K.
    Bhabha Atomic Research Centre, India.
    Bhatt, N.
    Bhabha Atomic Research Centre, India.
    Venugopal, K.
    Bhabha Atomic Research Centre, India.
    Goyal, H. C.
    Bhabha Atomic Research Centre, India.
    Kothari, M.
    Bhabha Atomic Research Centre, India.
    Chandra, P.
    Bhabha Atomic Research Centre, India.
    Rannot, R. C.
    Bhabha Atomic Research Centre, India.
    Dhar, V. K.
    Bhabha Atomic Research Centre, India.
    Koul, M. K.
    Bhabha Atomic Research Centre, India.
    Kaul, R. K.
    Bhabha Atomic Research Centre, India.
    Kotwal, S.
    Bhabha Atomic Research Centre, India.
    Chanchalani, K.
    Bhabha Atomic Research Centre, India.
    Thoudam, Satyendra
    Bhabha Atomic Research Centre, India.
    Chouhan, N.
    Bhabha Atomic Research Centre, India.
    Sharma, M.
    Bhabha Atomic Research Centre, India.
    Bhattacharyya, S.
    Bhabha Atomic Research Centre, India.
    Sahayanathan, S.
    Bhabha Atomic Research Centre, India.
    The TACTIC atmospheric Cherenkov imaging telescope2007In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 578, no 3, p. 548-564Article in journal (Refereed)
    Abstract [en]

    The TACTIC (TeV Atomospheric Cherenkov Telescope with Imaging Camera) γγ-ray telescope, equipped with a light collector of area ∼9.5m2 and a medium resolution imaging camera of 349 pixels, has been in operation at Mt. Abu, India, since 2001. This paper describes the main features of its various subsystems and its overall performance with regard to (a) tracking accuracy of its two-axes drive system, (b) spot size of the light collector, (c) back-end signal processing electronics and topological trigger generation scheme, (d) data acquisition and control system and (e) relative and absolute gain calibration methodology. Using a trigger field-of-view of 11×1111×11 pixels (∼3.4×3.4)(∼3.4∘×3.4∘), the telescope records a cosmic ray event rate of ∼2.5Hz at a typical zenith angle of 1515∘. Monte Carlo simulation results are also presented in the paper for comparing the expected performance of the telescope with actual observational results. The consistent detection of a steady signal from the Crab Nebula above ∼1.2TeV energy, at a sensitivity level of ∼5.0σ∼5.0σ in ∼25h, alongwith excellent matching of its energy spectrum with that obtained by other groups, reassures that the performance of the TACTIC telescope is quite stable and reliable. Furthermore, encouraged by the detection of strong γγ-ray signals from Mrk 501 (during 1997 and 2006 observations) and Mrk 421 (during 2001 and 2005–2006 observations), we believe that there is considerable scope for the TACTIC telescope to monitor similar TeV γγ-ray emission activity from other active galactic nuclei on a long-term basis.

  • 32.
    Moldón, J.
    et al.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands .
    Deller, A. T.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands .
    Wucknitz, O.
    Max-Planck-Institut für Radioastronomie, Germany.
    Jackson, N.
    The University of Manchester, UK.
    Drabent, A.
    Thüringer Landessternwarte, Germany.
    Carozzi, T.
    Chalmers University of Technology.
    Conway, J.
    Chalmers University of Technology.
    Kapinska, A. D.
    University of Portsmouth, UK ; University of Sydney, Australia ; .
    McKean, J. P.
    ASTRON, the Netherlands Institute for Radio Astronomy, Nehterlands.
    Morabito, L.
    Leiden University, The Netherlands .
    Varenius, E.
    Chalmers University of Technology.
    Zarka, P.
    Univ. Paris-Diderot, France .
    Anderson, J.
    DeutschesGeoForschungsZentrum GFZ, Germany.
    Asgekar, A.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands ; ShellTechnology Center, India .
    Avruch, I. M.
    SRON Netherlands Insitute for Space Research, The Netherlands.
    Bell, M. E.
    CSIRO Australia Telescope National Facility, Australia .
    Bentum, M. J.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands ; University of Twente, The Netherlands .
    Bernardi, G.
    Harvard-Smithsonian Center for Astrophysics, USA.
    Best, P.
    University of Edinburgh, UK.
    Bîrzan, L.
    Leiden University, The Netherlands .
    Bregman, J.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands .
    Breitling, F.
    Leibniz-Institut für Astrophysik Potsdam, Germany.
    Broderick, J. W.
    University of Oxford, UK ; University of Southampton UK.
    Brüggen, M.
    University of Hamburg, Germany.
    Butcher, H. R.
    Australian National University, Australia .
    Carbone, D.
    University of Amsterdam, The Netherlands .
    Ciardi, B.
    Max Planck Institute for Astrophysics, Germany.
    de Gasperin, F.
    University of Hamburg, Germany.
    de Geus, E.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands ; SmarterVision BV, The Netherland .
    Duscha, S.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands .
    Eislöffel, J.
    Thüringer Landessternwarte, Germany.
    Engels, D.
    Hamburger Sternwarte, Germany.
    Falcke, H.
    Radboud University Nijmegen, The Netherlands ; ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands .
    Fallows, R. A.
    ASTRON, the Netherlands Institute for Radio Astronomy, The Netherlands .
    Fender, R.
    University of Oxford, UK