Detection of the γ-ray binary LSI +61°303 in a low-flux state at very high energy γ-rays with the magic telescopes in 2009

Aleksić, J.; Alvarez, E. A.; Antonelli, L. A.; Antoranz, P.; Asensio, M.; Backes, M.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, Giacomo; Borla Tridon, D.; Bosch Ramon, V.; Braun, I.; Bretz, T.; Cañellas, A.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Cea del Pozo, E.; De Lotto, B.; Delgado Mendez, C.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido, D.; Giavitto, G.; Godinović, N.; Hadasch, D.; Häfner, D.; Herrero, A.; Hildebrand, D.; Höhne Mönch, D.; Hose, J.; Hrupec, D.; Huber, B.; Jogler, T.; Kellermann, H.; Klepser, S.; Krähenbühl, T.; Krause, J.; La Barbera, A.; Lelas, D.; Leonardo, Elvira; Lindfors, E.; Lombardi, S.; López, A.; López, M.; Lorenz, E.; Makariev, M.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, Mario; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moralejo, A.; Munar Adrover, P.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paneque, D.; Paoletti, Riccardo; Pardo, S.; Paredes, J. M.; Partini, Serena; Pasanen, M.; Pauss, F.; Perez Torres, M. A.; Persic, M.; Peruzzo, L.; Pilia, M.; Pochon, J.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, Antonio; Steinke, B.; Storz, J.; Strah, N.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Treves, A.; Uellenbeck, M.; Vankov, H.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.

doi:10.1088/0004-637X/746/1/80

We present very high energy (E > 100GeV) γ-ray observations of the γ-ray binary system LS I +61°303 obtained with the MAGIC stereo system between 2009 October and 2010 January. We detect a 6.3σ γ-ray signal above 400GeV in the combined data set. The integral flux above an energy of 300GeV is F(E > 300 GeV) = (1.4 ± 0.3stat ± 0.4syst) × 10-12 cm-2 s-1, which corresponds to about 1.3% of the Crab Nebula flux in the same energy range. The orbit-averaged flux of LS I +61°303 in the orbital phase interval 0.6-0.7, where a maximum of the TeV flux is expected, is lower by almost an order of magnitude compared to our previous measurements between 2005 September and 2008 January. This provides evidence for a new low-flux state in LS I +61°303. We find that the change to the low-flux state cannot be solely explained by an increase of photon-photon absorption around the compact star. © 2012. The American Astronomical Society. All rights reserved.

J., A., E. A., A., L. A., A., P., A., M., A., M., B., et al. (2012). Detection of the γ-ray binary LSI +61°303 in a low-flux state at very high energy γ-rays with the magic telescopes in 2009. THE ASTROPHYSICAL JOURNAL, 746(1) [10.1088/0004-637X/746/1/80].