Article

Detection of VHE \gamma-rays from HESS J0632+057 during the 2011 February X-ray outburst with the MAGIC Telescopes

The MAGIC Collaboration, J. Aleksić, E. A. Alvarez, L. A. Antonelli, P. Antoranz, M. Asensio, M. Backes, U. Barres de Almeida, J. A. Barrio, D. Bastieri, J. Becerra González, W. Bednarek, K. Berger, E. Bernardini, A. Biland, O. Blanch, R. K. Bock, A. Boller, G. Bonnoli, D. Borla Tridon, V. Bosch-Ramon, T. Bretz, A. Cañellas, E. Carmona, A. Carosi, P. Colin, E. Colombo, J. L. Contreras, J. Cortina, L. Cossio, S. Covino, P. Da Vela, F. Dazzi, A. De Angelis, G. De Caneva, E. De Cea del Pozo, B. De Lotto, C. Delgado Mendez, A. Diago Ortega, M. Doert, A. Domínguez, D. Dominis Prester, D. Dorner, M. Doro, D. Eisenacher, D. Elsaesser, D. Ferenc, M. V. Fonseca, L. Font, C. Fruck, R. J. García López, M. Garczarczyk, D. Garrido Terrats, G. Giavitto, N. Godinović, A. González Muñoz, S. R. Gozzini, D. Hadasch, D. Häfner, A. Herrero, D. Hildebrand, J. Hose, D. Hrupec, B. Huber, F. Jankowski, T. Jogler, V. Kadenius, H. Kellermann, S. Klepser, T. Krähenbühl, J. Krause, A. La Barbera, D. Lelas, E. Leonardo, N. Lewandowska, E. Lindfors, S. Lombardi, M. López, R. López-Coto, A. López-Oramas, E. Lorenz, M. Makariev, G. Maneva, N. Mankuzhiyil, K. Mannheim, L. Maraschi, M. Mariotti, M. Martínez, D. Mazin, M. Meucci, J. M. Miranda, R. Mirzoyan, J. Moldón, A. Moralejo, P. Munar-Adrover, A. Niedzwiecki, D. Nieto, K. Nilsson, N. Nowak, R. Orito, S. Paiano, D. Paneque, R. Paoletti, S. Pardo, J. M. Paredes, S. Partini, M. A. Perez-Torres, M. Persic, M. Pilia, J. Pochon, F. Prada, P. G. Prada Moroni, E. Prandini, I. Puerto Gimenez, I. Puljak, I. Reichardt, R. Reinthal, W. Rhode, M. Ribó, J. Rico, S. Rügamer, A. Saggion, K. Saito, T. Y. Saito, M. Salvati, K. Satalecka, V. Scalzotto, V. Scapin, C. Schultz, T. Schweizer, S. N. Shore, A. Sillanpää, J. Sitarek, I. Snidaric, D. Sobczynska, F. Spanier, S. Spiro, V. Stamatescu, A. Stamerra, B. Steinke, J. Storz, N. Strah, S. Sun, T. Surić, L. Takalo, H. Takami, F. Tavecchio, P. Temnikov, T. Terzić, D. Tescaro, M. Teshima, O. Tibolla, D. F. Torres, A. Treves, M. Uellenbeck, P. Vogler, R. M. Wagner, Q. Weitzel, V. Zabalza, F. Zandanel, R. Zanin, now at: Ecole polytechnique fédérale de Lausanne, Lausanne, Switzerland, supported by INFN Padova, now at: Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Madrid, Spain, now at: KIPAC, SLAC National Accelerator Laboratory, USA, now at: Finnish Centre for Astronomy with ESO, University of Turku, Finland

03/2012;
Source: arXiv

ABSTRACT The very high energy (VHE) \gamma-ray source HESS J0632+057 has recently been
confirmed to be a \gamma-ray binary. The optical counterpart is the Be star MWC
148, and a compact object of unknown nature orbits it every ~321 d with a high
eccentricity of ~0.8. We monitored HESS J0632+057 with the stereoscopic MAGIC
telescopes from 2010 October to 2011 March and detected significant VHE
\gamma-ray emission during 2011 February, when the system exhibited an X-ray
outburst. We find no \gamma-ray signal in the other observation periods when
the system did not show increased X-ray flux. Thus HESS J0632+057 exhibits
\gamma-ray variability on timescales of the order of one to two months possibly
linked to the X-ray outburst that takes place about 100 days after the
periastron passage. Furthermore our measurements provide for the first time the
\gamma-ray spectrum down to about 140 GeV and indicate no turnover of the
spectrum at low energies. We compare the properties of HESS J0632+057 with the
similar \gamma-ray binary LS I +61 303, and discuss on the possible origin of
the multi-wavelength emission of the source

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Keywords

\gamma-ray binary
 
\gamma-ray signal
 
\gamma-ray spectrum
 
\gamma-ray variability
 
compact
 
eccentricity
 
measurements
 
observation periods
 
periastron passage
 
possible origin
 
similar \gamma-ray binary LS
 
system exhibited
 
timescales
 
unknown nature orbits
 
VHE
 
X-ray flux
 
X-ray outburst