Multiwavelength observations of the lensed quasar PKS 1830-211 during the 2019 γ-ray flare
Morselli, A.; Chen, A. W.; Iacolina, M. N.; Egron, E.; Pilia, M.; Capitanio, F.; Righini, S.; Valente, G.; Melis, A.; Pili, M.; De Rosa, A.; Readhead, A. C. S.; Puccetti, S.; Di Gesu, L.; Donnarumma, I.; Trois, A.; Hovatta, T.; Vercellone, S.; Pacciani, L.; Verrecchia, F.; Vittorini, V.; Tavani, M.; Bulgarelli, A.; Cattaneo, P. W.; Piano, G.; Pittori, C.; Lucarelli, F.; Max-Moerbeck, W.; Reeves, R.; Brocato, E.; Kiehlmann, S.; Vitali, F.; Ridolfi, A.; Perrodin, D.; Pellizzoni, P. A.
Italy, Greece, South Africa, Finland, Chile, United States
Abstract
PKS 1830 -211 is a γ-ray emitting, high-redshift (z =2.507 ± 0.002), lensed flat-spectrum radio quasar. During the period 2019 mid-February to mid-April, this source underwent a series of strong γ-ray flares that were detected by both AGILE-GRID (Gamma-Ray Imaging Detector) and Fermi Large Area Telescope (Fermi-LAT), reaching a maximum γ-ray flux of $F_{\rm E\gt 100\, MeV}\approx 2.3\times 10^{-5}$ photons cm-2 s-1. Here, we report on a coordinated campaign from both on-ground [Medicina, Owens Valley Radio Observatory (OVRO), Rapid Eye Mount (REM), and Sardinia Radio Telescope (SRT)] and orbiting facilities (AGILE, Fermi, INTEGRAL, NuSTAR, Swift, and Chandra), with the aim of investigating the multiwavelength properties of PKS 1830-211 through nearly simultaneous observations presented here for the first time. We find a possible break in the radio spectra in different epochs above 15 GHz, and a clear maximum of the 15 GHz data approximately 110 d after the γ-ray main activity periods. The spectral energy distribution shows a very pronounced Compton dominance (> 200) which challenges the canonical one-component emission model. Therefore, we propose that the cooled electrons of the first component are re-accelerated to a second component by, for example, kink or tearing instability during the γ-ray flaring periods. We also note that PKS 1830-211 could be a promising candidate for future observations with both Compton satellites [e.g. enhanced ASTROGAM (e-ASTROGAM)] and Cherenkov arrays [Cherenkov Telescope Array Observatory (CTAO)] which will help, thanks to their improved sensitivity, in extending the data availability in energy bands currently uncovered.