MAGICal GRB 190114C: Implications of cutoff in the spectrum at sub-$GeV$ energies

Abstract

GRB 190114C is a famous Gamma-Ray Burst (GRB) due to its detection at sub-T eV energies by MAGIC, seen at redshift z = 0.42. This burst is one of the brightest GRB detected by Fermi . We present a detailed analysis of GRB 190114C prompt emission, using the two Fermi detectors: GBM and LAT. The LAT low energy events (LLE) data is also considered. A joint GBM-LAT analysis reveals a sub-GeV spectral cutoff. A similar high energy cutoff was reported in GRB 160509A and GRB 100724B earlier, and a handful of other sources. The cutoff can be explained by the intrinsic opacity due to pair production within the emitting region. Such morphology in these GRBs suggests that they belong to one specific class having a similar source of the radiation mechanism. GRB 190114C shows a transition from non-thermal to a quasi-thermal-like spectrum along with radiation due to external shock. From spectrum analysis and Lorentz factor evolution from the trigger time to late emission, considering the fact that sub-T eV photons are detected in MAGIC, we are able to draw an emission mechanism picture, where the prompt emission spectrum is more consistent with spectrum via photospheric dissipation with presence of external shock emission simultaneously.

Peculiar prompt emission and afterglow in H.E.S.S. detected GRB 190829A

“…and MAGIC to get a global picture and capture the diversity of these events. Studies on GRB 190114C showed multiple components in its prompt emission and a standard afterglow (Wang et al 2019;Chand et al 2019;Fraija et al 2019a). GRB 180720B showed synchrotron spectrum for prompt and a standard afterglow (Ronchi et al 2019;Fraija et al 2019b).…”