Analysis and Modeling of the Multi-wavelength Observations of the Luminous GRB 190114C

Abstract

Very-high-energy (VHE; ≥ 10 GeV) photons are expected from the nearest and brightest Gamma-ray bursts (GRBs). VHE photons, at energies higher than 300 GeV, were recently reported by the MAGIC collaboration for this burst. Immediately, GRB 190114C was followed up by a massive observational campaign covering a large fraction of the electromagnetic spectrum. In this paper, we obtain the LAT light curve of GRB 190114C and show that it exhibits similar features to other bright LAT-detected bursts; the first high-energy photon (≥ 100 MeV) is delayed with the onset of the prompt phase and the flux light curve exhibits a long-lived emission (lasting much longer than the prompt phase) and a short-lasting bright peak (located at the beginning of long-lived emission). Analyzing the multi-wavelength observations, we show that the short-lasting LAT and GBM bright peaks are consistent with the synchrotron self-Compton reverse-shock model and the long-lived observations with the standard synchrotron forward-shock model that evolves from a stratified stellar-wind like medium to a uniform ISM-like medium. Given the best-fit values, a bright optical flash produced by synchrotron reverse-shock emission is expected. From our analysis we infer that the high-energy photons are produced in the deceleration phase of the outflow and some additional processes to synchrotron in the forward shocks should be considered to properly describe the LAT photons with energies beyond the synchrotron limit. Moreover, we claim that an outflow endowed with magnetic fields could describe the polarization and properties exhibited in the light curve of GRB 190114C.

East Asia VLBI Network observations of the TeV Gamma-Ray Burst 190114C

“…Wang et al 2019 [38] model the multi-wavelength emission after ∼1ks as synchrotron radiation from the forward shock. A similar modelling is proposed by Fraija et al [39], where the early optical/X-ray emission is instead interpreted as due to the deceleration of the jet in a wind-like stratified medium. The radio (1.3-97 GHz) emission in the early phase up to ∼1ks has been interpreted as due to the emission by the transient reverse shock that marks the time during which the jet injects its energy into the shocked region [40].…”

“…The radio (1.3-97 GHz) emission in the early phase up to ∼1ks has been interpreted as due to the emission by the transient reverse shock that marks the time during which the jet injects its energy into the shocked region [40]. At present two possible scenarios seem to emerge in the interpretation of the available multi-wavelength data: either emission from the reverse/forward shock component in a wind medium (where the reverse and forward shock emission dominate the early-and late-time emission, respectively) or emission dominated solely by the forward shock produced by the expansion of the outflow in a medium whose density evolves from a wind environment to an interstellar medium (ISM) with a constant number density [39].…”

GRB Fermi-LAT Afterglows: Explaining Flares, Breaks, and Energetic Photons

“…The value of the initial bulk Lorentz factor inferred during the deceleration phase is similar to those reported by other burst detected by Fermi-LAT (Veres & Mészáros 2012). Since GRB 160509A exhibited one of the most energetic photons reported by Fermi-LAT in the second GRB catalog, it is expected that the value of the bulk Lorentz factor lies in the range of the brightest LAT-detected bursts (500Γ1000; Abdo et al 2009a;Ackermann 2010;Ackermann et al 2011;Ackermann 2013;Ackermann et al 2014;Fraija et al 2019bFraija et al , 2019c, as found in this work.…”

Neutron star mergers and how to study them

“…From the conditions in GRB jets we generically expect Synchrotron Self Compton (SSC) emission. The first public claim of VHE detection of a GRB was for GRB 190114C (Mirzoyan et al 2019), which has been modeled with a SSC origin (e.g., Fraija et al 2019;Derishev and Piran 2019;Wang et al 2019). However, no analysis published so far has performed robust multi-instrument spectral analysis showing a statistical preference for a SSC origin against a base synchrotron explanation, which may also fit the data.…”