MAGIC observation and broadband characterization of the remarkably bright flares of 1ES 1959+650 in 2016
July 22, 2019
1ES 1959+650 is a bright TeV high-frequency peaked BL Lac object exhibiting interesting fea-
tures like broad high energy peak in the spectral energy distribution (SED) and "orphan" TeV
flares, that are difficult to interpret using a conventional one-zone synchrotron self-Compton
(SSC) scenario. We report the results from MAGIC observations in 2016 along with the multi-
wavelength data from Fermi-LAT and Swift instruments. An exceptionally high very-high-energy
(VHE) flux reaching ∼ 3 times the Crab Nebula flux was measured by MAGIC on 13th, 14th
June and 1st July 2016. It is the highest flux level observed since 2002. During these flares, the
second SED peak lies in the VHE domain, and the spectrum extends up to several TeV energies.
The LAT and X-ray spectra are also hard with index < 2.On 13th June, the source showed fast
variabilities in the VHE flux with timescales less than an hour. A simple one-zone SSC model can
satisfactorily describe the data during the high VHE states requiring a Doppler factor δ ≤ 30–60.
Alternatively, the SED can be explained by synchrotron radiation of relativistic protons with a
reasonable jet power L jet ∼ 10 46 erg · s −1 under the requirement of high magnetic fields B ∼ 100
G and maximum proton energy ∼ few EeV. The theoretical models imply that detecting neutrino
emission from the source during a similar flare with the extreme VHE flaring period of 2016 is
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