The bright gamma-ray flare of 3C 279 in 2015 June: AGILE detection and multifrequency follow-up observations
Pittori, Carlotta; Lucarelli, Fabrizio; Verrecchia, Francesco; Raiteri, Claudia Maria; Villata, M.; Vittorini, Valerio; Tavani, Marco; Puccetti, Simonetta; Perri, M.; Donnarumma, I.; Vercellone, Stefano; Acosta-Pulido, J. A.; Bachev, R.; Benitez, E.; Borman, G. A.; Carnerero, M. I.; Carosati, D.; Chen, W. P.; Ehgamberdiev, Sh. A.; Goded, A.; Grishina, T. S.; Hiriart, D.; Hsiao, H. Y.; Jorstad, Svetlana G.; Kimeridze, G. N.; Kopatskaya, E. N.; Kurtanidze, O. M.; Kurtanidze, S. O.; Larionov, Valeri M.; Larionova, L. V.; Marscher, Alan P.; Mirzaqulov, D. O.; Morozova, Daria A.; Nilsson, K.; Samal, M. R.; Sigua, L. A.; Spassov, B.; Strigachev, A.; Takalo, L. O.; Antonelli, L. A.; Bulgarelli, A.; Cattaneo, P.; Colafrancesco, S.; Giommi, P.; Longo, F.; Morselli, Aldo; Paoletti, F.
We report the AGILE detection and the results of the multifrequency follow-up observations of a bright γ-ray flare of the blazar 3C 279 in 2015 June. We use AGILE and Fermi gamma-ray data, together with Swift X-ray andoptical-ultraviolet data, and ground-based GASP-WEBT optical observations, including polarization information, to study the source variability and the overall spectral energy distribution during the γ-ray flare. The γ-ray flaring data, compared with as yet unpublished simultaneous optical data that will allow constraints on the big blue bump disk luminosity, show very high Compton dominance values of ~100, with the ratio of γ-ray to optical emission rising by a factor of three in a few hours. The multiwavelength behavior of the source during the flare challenges one-zone leptonic theoretical models. The new observations during the 2015 June flare are also compared with already published data and nonsimultaneous historical 3C 279 archival data.
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