QSO B0218+357 is currently the only gravitationally lensed source from which both high-energy (HE, >~100 MeV) and very-high-energy (VHE,>~100GeV) gamma-ray emission has been detected.
We report the Fermi/LAT and multiwavelength monitoring observations of this source in radio interferometry, optical and X-rays performed between 2016 and 2020. During the monitoring, individual flares in the optical, X-ray and HE bands were observed.
We analysed the MAGIC telescopes data during the flaring states to
search for the associated VHE emission, constraining the VHE gamma-ray
duty cycle of the source.
We model the quiescent emission in which the high-energy bump
is explained as a combination of Synchrotron-Self-Compton and External
Compton processes. The bulk of the low-energy emission is explained as
originating from a tens of parsecs scale jet.