Gamma-ray and x-ray observations of the periodic-repeater frb 180916 during active phases

36siFRB 180916 is a most intriguing source capable of producing repeating fast radio bursts with a periodic 16.3 day temporal pattern. The source is well positioned in a star-forming region in the outskirts of a nearby galaxy at 150 Mpc distance. In this Letter we report on the X-ray and γ-ray observations of FRB 180916 obtained by AGILE and Swift. We focused especially on the recurrent 5 day time intervals of enhanced radio bursting. In particular, we report on the results obtained in the time intervals 2020 February 3-8, 2020 February 25, 2020 March 5-10, and 2020 March 22-28 during a multiwavelength campaign involving high-energy and radio observations of FRB 180916. We also searched for temporal coincidences at millisecond timescales between the 32 known radio bursts of FRB 180916 and X-ray and MeV events detectable by AGILE. We do not detect any simultaneous event or any extended X-ray and γ-ray emission on timescales of hours/days/weeks. Our cumulative X-ray (0.3-10 keV) flux upper limit of 5 × 10-14erg cm-2s-1(obtained during 5 day active intervals from several 1-2 ks integrations) translates into an isotropic luminosity upper limit of LX,UL∼ 1.5 × 1041erg s-1. Deep γ-ray observations above 100 MeV over a many-year timescale provide an average luminosity upper limit one order of magnitude larger. These results provide the so-far most stringent upper limits on high-energy emission from the FRB 180916 source. Our results constrain the dissipation of magnetic energy from a magnetar-like source of radius Rm, internal magnetic field Bm, and dissipation timescale τdto satisfy the relation R3m6B2m16 t-1d8≲1,where Rm,6is Rmin units of 106cm, Bm,16is Bmin units of 1016G, and τd,8in units of 108s.nonemixedTavani M.; Verrecchia F.; Casentini C.; Perri M.; Ursi A.; Pacciani L.; Pittori C.; Bulgarelli A.; Piano G.; Pilia M.; Bernardi G.; Addis A.; Antonelli L.A.; Argan A.; Baroncelli L.; Caraveo P.; Cattaneo P.W.; Chen A.; Costa E.; Persio G.D.; Donnarumma I.; Evangelista Y.; Feroci M.; Ferrari A.; Fioretti V.; Lazzarotto F.; Longo F.; Morselli A.; Paoletti F.; Parmiggiani N.; Trois A.; Vercellone S.; Naldi G.; Pupillo G.; Bianchi G.; Puccetti S.Tavani, M.; Verrecchia, F.; Casentini, C.; Perri, M.; Ursi, A.; Pacciani, L.; Pittori, C.; Bulgarelli, A.; Piano, G.; Pilia, M.; Bernardi, G.; Addis, A.; Antonelli, L. A.; Argan, A.; Baroncelli, L.; Caraveo, P.; Cattaneo, P. W.; Chen, A.; Costa, E.; Persio, G. D.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Ferrari, A.; Fioretti, V.; Lazzarotto, F.; Longo, F.; Morselli, A.; Paoletti, F.; Parmiggiani, N.; Trois, A.; Vercellone, S.; Naldi, G.; Pupillo, G.; Bianchi, G.; Puccetti, S