Research Note

MAGIC observations of MWC 656, the only known Be/BH system

¹ IFAE, Campus UAB 08193 Bellaterra Spain
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 Max-Planck-Institut für Physik, 80805 München, Germany
⁷ Universidad Complutense, 28040 Madrid, Spain
⁸ Inst. de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
⁹ University of Łódź, 90236 Lodz, Poland
¹⁰ Deutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, Germany
¹¹ ETH Zurich, 8093 Zurich, Switzerland
¹² Universität Würzburg, 97074 Würzburg, Germany
¹³ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, 28040 Madrid, Spain
¹⁴ Institute of Space Sciences, 08193 Barcelona, Spain
¹⁵ Università di Padova and INFN, 35131 Padova, Italy
¹⁶ Technische Universität Dortmund, 44221 Dortmund, Germany
¹⁷ Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
¹⁸ Universitat de Barcelona, ICC, IEEC-UB, 08028 Barcelona, Spain
¹⁹ Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan
²⁰ Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, 90014 Oulun, Finland
²¹ Inst. for Nucl. Research and Nucl. Energy, 1784 Sofia, Bulgaria
²² Università di Pisa, and INFN Pisa, 56126 Pisa, Italy
²³ ICREA and Institute of Space Sciences, 08193 Barcelona, Spain
²⁴ Università dell’Insubria and INFN Milano Bicocca, Como, 22100 Como, Italy
²⁵ 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
²⁶ Now at: École polytechnique fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
²⁷ Now at: Institut für Astro- und Teilchenphysik, Leopold-Franzens- Universität Innsbruck, 6020 Innsbruck, Austria
²⁸ Now at: Finnish Centre for Astronomy with ESO (FINCA), 20014 Turku, Finland
²⁹ Now at: Astrophysics Science Division, Bhabha Atomic Research Centre, 400085 Mumbai, India
³⁰ Also at INAF-Trieste  
³¹ Now at: ASTRON Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands

Received: 29 August 2014
Accepted: 5 February 2015

Abstract

Context. MWC 656 has recently been established as the first observationally detected high-mass X-ray binary system containing a Be star and a black hole (BH). The system has been associated with a gamma-ray flaring event detected by the AGILE satellite in July 2010.

Aims. Our aim is to evaluate whether the MWC 656 gamma-ray emission extends to very high energy (VHE > 100 GeV) gamma rays.

Methods. We observed MWC 656 with the MAGIC telescopes for ~23 h during two observation periods: between May and June 2012, and in June 2013. During the last period, observations were performed contemporaneously with X-ray (XMM-Newton) and optical (STELLA) instruments.

Results. We did not detect the MWC 656 binary system at TeV energies with the MAGIC telescopes in either of the two campaigns. Upper limits (ULs) to the integral flux above 300 GeV have been set, as well as differential ULs at a level of ~5% of the Crab nebula flux. The results obtained from the MAGIC observations do not support persistent emission of VHE gamma rays from this system at a level of 2.4% the Crab flux.