Proton Synchrotron, an explanation for possible extended VHE gamma-ray activity of TXS 0506+056 in 2017

Sunanda, Reetanjali Moharana, Pratik Majumdar

Submitted on 4 November 2022


TXS 0506+056, a source of the extreme energy neutrino event, IceCube-170922A, was observed on 22 September 2017. The Fermi-LAT detector reported high energy (HE) γ-ray flare between 100 MeV and 100 GeV starting from 15 September 2017 from this source. Several attempts to trace the very high energy (VHE) gamma-ray counterparts around the IceCube-170922A resulted in no success. Only after 28 September, the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes observed the first VHE gamma-rays from the blazar above 100 GeV. The 41 hr survey resulted in VHE-γ ray activity till 31 October 2017. Here we propose the extended GeV γrays can be explained by taking two production channels, electron synchrotron self Compton and proton synchrotron for HE and VHE emissions, respectively. The 45 days of VHE emission from the peak of the HE-flare can be explained with Lp1047 erg/sec in the jet frame and magnetic field of 2.4 G, consistent with the LEdd for a blackhole mass 5×109M


Subjects: Astrophysics - High Energy Astrophysical Phenomena; High Energy Physics - Phenomenology


The Fermi-LAT light curve of TXS 0506+056 blazar for energy range 1 to 300 GeV between MJD 57997-58253 with 7-day bin. The (red) dotted line shows the correlated IceCube-170922A neutrino event within the HE flaring episode 58008-58021 MJD. The shadow region indicates the time period of VHE activity observed by MAGIC. The square points represent the MAGIC events reported in \cite{2022ApJ...927..197A}.