Variable very-high-energy gamma-ray emission from the microquasar LS I +61 303

Albert, J.; Aliu, E.; Anderhub, H.; Antoranz, P.; Armada, A.; Asensio, M.; Baixeras, C.; Barrio, Ja; Bartelt, M.; Bartko, H.; Bastieri, D.; Bavikadi, Sr; Bednarek, W.; Berger, K.; Bigongiari, C.; Biland, A.; Bisesi, E.; Bock, Rk; Bordas, P.; Bosch Ramon, V.; Bretz, T.; Britvitch, I.; Camara, M.; Carmona, E.; Chilingarian, A.; Ciprini, S.; Coarasa, Ja; Commichau, S.; Contreras, Jl; Cortina, J.; Curtef, V.; Danielyan, V.; Dazzi, F.; DE ANGELIS, Alessandro; de los Reyes, R.; DE LOTTO, Barbara; Domingo Santamaria, E.; Dorner, D.; Doro, M.; Errando, M.; Fagiolini, M.; Ferenc, D.; Fernandez, E.; Firpo, R.; Flix, J.; Fonseca, Mv; Font, L.; Fuchs, M.; Galante, N.; Garczarczyk, M.; Gaug, M.; Giller, M.; Goebel, F.; Hakobyan, D.; Hayashida, M.; Hengstebeck, T.; Hohne, D.; Hose, J.; Hsu, Cc; Isar, Pg; Jacon, P.; Kalekin, O.; Kosyra, R.; Kranich, D.; Laatiaoui, M.; Laille, A.; Lenisa, T.; Liebing, P.; Lindfors, E.; Lombardi, S.; Longo, F.; Lopez, J.; Lopez, M.; Lorenz, E.; Lucarelli, F.; Majumdar, P.; Maneva, G.; Mannheim, K.; Mansutti, O.; Mariotti, M.; Martinez, M.; Mase, K.; Mazin, D.; Merck, C.; Meucci, M.; Meyer, M.; Miranda, Jm; Mirzoyan, R.; Mizobuchi, S.; Moralejo, A.; Nilsson, K.; Ona Wilhelmi, E.; Orduna, R.; Otte, N.; Oya, I.; Paneque, D.; Paoletti, R.; Paredes, Jm; Pasanen, M.; Pascoli, D.; Pauss, F.; Pavel, N.; Pegna, R.; Persic, M.; Peruzzo, L.; Piccioli, A.; Poller, M.; Pooley, G.; Prandini, E.; Raymers, A.; Rhode, W.; Ribo, M.; Rico, J.; Riegel, B.; Rissi, M.; Robert, A.; Romero, Ge; Rugamer, S.; Saggion, A.; Sanchez, A.; Sartori, P.; Scalzotto, V.; Scapin, V.; Schmitt, R.; Schweizer, T.; Shayduk, M.; Shinozaki, K.; Shore, Sn; Sidro, N.; Sillanpaa, A.; Sobczynska, D.; Stamerra, A.; Stark, Ls; Takalo, L.; Temnikov, P.; Tescaro, D.; Teshima, M.; Tonello, N.; Torres, A.; Torres, Df; Turini, N.; Vankov, H.; Vitale, V.; Wagner, Rm; Wibig, T.; Wittek, W.; Zanin, R.; Zapatero, J.

doi:10.1126/science.1128177

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LSI+61 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.