Very high-energy γ-ray observations of novae and dwarf novae with the MAGIC telescopes^⋆

¹ ETH Zurich, 8093 Zurich, Switzerland
² Università di Udine, and INFN Trieste, 33100 Udine, Italy
³ INAF National Institute for Astrophysics, 00136 Rome, Italy
⁴ Università di Siena, and INFN Pisa, 53100 Siena, Italy
⁵ Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, 10000 Zagreb, Croatia
⁶ Saha Institute of Nuclear Physics, 1\AF Bidhannagar, Salt Lake, Sector-1, 700064 Kolkata, India
⁷ Max-Planck-Institut für Physik, 80805 München, Germany
⁸ Universidad Complutense, 28040 Madrid, Spain
⁹ Inst. de Astrofísica de Canarias, 38200, La Laguna, Tenerife Spain
¹⁰ University of Łódź, 90236 Lodz, Poland
¹¹ Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
¹² IFAE, Campus UAB, 08193 Bellaterra, Spain
¹³ Universität Würzburg, 97074 Würzburg, Germany
¹⁴ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, 28040 Madrid, Spain
¹⁵ Università di Padova and INFN, 35131 Padova, Italy
¹⁶ Institute of Space Sciences, 08193 Barcelona, Spain
¹⁷ Technische Universität Dortmund, 44221 Dortmund, Germany
¹⁸ Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
¹⁹ Universitat de Barcelona, ICC, IEEC-UB, 08028 Barcelona, Spain
²⁰ Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, KEK, 770-0855 Tokushima, Japan
²¹ Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, 90014 Oulu, Finland
²² Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
²³ Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
²⁴ ICREA and Institute of Space Sciences, 08193 Barcelona, Spain
²⁵ Università dell’Insubria and INFN Milano Bicocca, Como, 22100 Como, Italy
²⁶ Now at Centro Brasileiro de Pesquisas Físicas (CBPF\MCTI), R. Dr. Xavier Sigaud, 150 – Urca, Rio de Janeiro – RJ, 22290-180, Brazil
²⁷ Now at NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA and Department of Physics and Department of Astronomy, University of Maryland, College Park, MD 20742, USA
²⁸ Humboldt University of Berlin, Institut für Physik Newtonstr. 15, 12489 Berlin, Germany
²⁹ Now at École polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
³⁰ Now at Finnish Centre for Astronomy with ESO (FINCA), Turku, Finland
³¹ Also at INAF – Trieste, Italy
³² Also at ISDC – Science Data Center for Astrophysics, 1290 Versoix (Geneva), Switzerland
³³ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 6 May 2015
Accepted: 17 August 2015

Abstract

Context. In the last five years the Fermi Large Area Telescope (LAT) instrument detected GeV γ-ray emission from five novae. The GeV emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. In this case it is expected that protons in the same conditions can be accelerated to much higher energies. Consequently they may produce a second component in the γ-ray spectrum at TeV energies.

Aims. We aim to explore the very high-energy domain to search for γ-ray emission above 50 GeV and to shed light on the acceleration process of leptons and hadrons in nova explosions.

Methods. We have performed observations, with the MAGIC telescopes of the classical nova V339 Del shortly after the 2013 outburst; optical and subsequent GeV γ-ray detections triggered the MAGIC observations. We also briefly report on VHE observations of the symbiotic nova YY Her and the dwarf nova ASASSN-13ax. We complement the TeV MAGIC observations with the analysis of contemporaneous Fermi-LAT data of the sources. The TeV and GeV observations are compared in order to evaluate the acceleration parameters for leptons and hadrons.

Results. No significant TeV emission was found from the studied sources. We computed upper limits on the spectrum and night-by-night flux. The combined GeV and TeV observations of V339 Del limit the ratio of proton to electron luminosities to L_p ≲ 0.15 L_e.