Detection of VHE γ-rays from HESS J0632+057 during the 2011 february X-ray outburst with the magic telescopes

Aleksic, J.; Alvarez, E. A.; Antonelli, L. A.; Antoranz, P.; Asensio, M.; Backes, M.; U. B., De; Barrio, J. A.; Bastieri, D.; Gonzalez, J. B.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, Giacomo; Tridon, D. B.; Bosch Ramon, V.; Bretz, T.; Canellas, A.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; Vela, P. D.; Dazzi, F.; Angelis, A. D.; Caneva, G. D.; Del, E. D.; Lotto, B. D.; Mendez, C. D.; Ortega, A. D.; Doert, M.; Dominguez, A.; Prester, D. D.; Dorner, D.; Doro, M.; Eisenacher, D.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; R. J. G.,; Garczarczyk, M.; Terrats, D. G.; Giavitto, G.; Godinovic, N.; Munoz, A. G.; Gozzini, S. R.; Hadasch, D.; Hafner, D.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Huber, B.; Jankowski, F.; Jogler, T.; Kadenius, V.; Kellermann, H.; Klepser, S.; Krahenbuhl, T.; Krause, J.; Barbera, A. L.; Lelas, D.; Leonardo, E.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Lopez, M.; Lopez Coto, R.; Lopez Oramas, A.; Lorenz, E.; Makariev, M.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martinez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moldon, J.; Moralejo, A.; Munar Adrover, P.; Niedzwiecki, A.; Nieto, D.; Nilsson, K.; Nowak, N.; Orito, R.; Paiano, S.; Paneque, D.; Paoletti, Riccardo; Pardo, S.; Paredes, J. M.; Partini, S.; Perez Torres, M. A.; Persic, M.; Pilia, M.; Pochon, J.; Prada, F.; P. G. P.,; Prandini, E.; Gimenez, I. P.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribo, M.; Rico, J.; Rugamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpaa, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamatescu, V.; Stamerra, Antonio; Steinke, B.; Storz, J.; Strah, N.; Sun, S.; Suric, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzic, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.

doi:10.1088/2041-8205/754/1/L10

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 similar to 321 days with a high eccentricity of similar to 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 degrees 303 and discuss the possible origin of the multi-wavelength emission of the source.

J., A., E. A., A., L. A., A., P., A., M., A., M., B., et al. (2012). Detection of VHE γ-rays from HESS J0632+057 during the 2011 february X-ray outburst with the magic telescopes. THE ASTROPHYSICAL JOURNAL LETTERS, 754(1) [10.1088/2041-8205/754/1/L10].