%0 Journal Article
%A Baquero Larriva, Orlando Andrés
%A Barrio Uña, Juan Abel
%A Contreras González, José Luis
%A Fonseca González, María Victoria
%A Hoang, Kim Dinh
%A López Moya, Marcos
%A Miener, Tjark
%A Morcuende, D.
%A Peñil Del Campo, Pablo
%A Saha, Lab
%T Detection of the Geminga pulsar with MAGIC hints at a power-law tail emission beyond 15 GeV
%D 2020
%@ 0004-6361
%U https://hdl.handle.net/20.500.14352/8258
%X We report the detection of pulsed gamma-ray emission from the Geminga pulsar (PSR J0633+1746) between 15 GeV and 75 GeV. This is the first time a middle-aged pulsar has been detected up to these energies. Observations were carried out with the MAGIC telescopes between 2017 and 2019 using the low-energy threshold Sum-Trigger-II system. After quality selection cuts, similar to 80 h of observational data were used for this analysis. To compare with the emission at lower energies below the sensitivity range of MAGIC, 11 years of Fermi-LAT data above 100 MeV were also analysed. From the two pulses per rotation seen by Fermi-LAT, only the second one, P2, is detected in the MAGIC energy range, with a significance of 6.3 sigma. The spectrum measured by MAGIC is well-represented by a simple power law of spectral index Gamma =5.62 +/- 0.54, which smoothly extends the Fermi-LAT spectrum. A joint fit to MAGIC and Fermi-LAT data rules out the existence of a sub-exponential cut-off in the combined energy range at the 3.6 sigma significance level. The power-law tail emission detected by MAGIC is interpreted as the transition from curvature radiation to Inverse Compton Scattering of particles accelerated in the northern outer gap.
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