Discovery of Powerful Gamma-Ray Flares from the Crab Nebula
Bignami, G. F.; Costa, E.; Mereghetti, S.; Heinke, C. O.; Barbiellini, G.; Longo, F.; Morselli, A.; Chen, A. W.; Giommi, P.; Di Cocco, G.; Pellizzoni, A.; De Luca, A.; Pilia, M.; Ferrigno, C.; Horns, D.; Gianotti, F.; Campana, R.; Feroci, M.; D'Ammando, F.; Del Monte, E.; Donnarumma, I.; Evangelista, Y.; Soffitta, P.; Trois, A.; Weisskopf, M. C.; Moretti, E.; Vercellone, S.; Pacciani, L.; Verrecchia, F.; Giusti, M.; Striani, E.; Vittorini, V.; Tavani, M.; Bulgarelli, A.; Giuliani, A.; Pucella, G.; Argan, A.; Caraveo, P.; Cattaneo, P. W.; Ferrari, A.; Fuschino, F.; Galli, M.; Labanti, C.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Marisaldi, M.; Morelli, E.; Perotti, F.; Piano, G.; Picozza, P.; Prest, M.; Rapisarda, M.; Rappoldi, A.; Rubini, A.; Sabatini, S.; Trifoglio, M.; Vallazza, E.; Zanello, D.; Pittori, C.; Santolamazza, P.; Lucarelli, F.; Salotti, L.; Tennant, A.; Contessi, T.; DeParis, G.; Di Persio, G.; Zambra, A.
Italy, United States, Germany, Switzerland, Canada, Russia
Abstract
The well-known Crab Nebula is at the center of the SN1054 supernova remnant. It consists of a rotationally powered pulsar interacting with a surrounding nebula through a relativistic particle wind. The emissions originating from the pulsar and nebula have been considered to be essentially stable. Here, we report the detection of strong gamma-ray (100 mega-electron volts to 10 giga-electron volts) flares observed by the AGILE satellite in September 2010 and October 2007. In both cases, the total gamma-ray flux increased by a factor of three compared with the non-flaring flux. The flare luminosity and short time scale favor an origin near the pulsar, and we discuss Chandra Observatory x-ray and Hubble Space Telescope optical follow-up observations of the nebula. Our observations challenge standard models of nebular emission and require power-law acceleration by shock-driven plasma wave turbulence within an approximately 1-day time scale.