Multi-messenger model for the prompt emission from GRB 221009A

TL;DR

This paper develops a multi-messenger model for GRB 221009A's prompt emission, integrating leptohadronic processes, and explores its implications for neutrino and UHECR observations, matching observed light curves and spectra.

Contribution

It introduces a comprehensive, time-dependent leptohadronic model for GRB prompt emission, including UHE protons and neutrino predictions, within the internal shock framework.

Findings

Reproduces observed light curves with variable ejection velocity.

Consistent with non-detection of neutrinos for certain baryonic loadings.

Inverse Compton scenarios predict higher gamma-ray fluxes detectable by Fermi.

Abstract

We present a multi-messenger model for the prompt emission from GRB 221009A within the internal shock scenario. We consider the time-dependent evolution of the outflow with its impact on the observed light curve from multiple collisions, and the self-consistent generation of the electromagnetic spectrum in synchrotron and inverse Compton-dominated scenarios. Our leptohadronic model includes UHE protons potentially accelerated in the outflow, and their feedback on spectral energy distribution and on the neutrino emission. We find that we can roughly reproduce the observed light curves with an engine with varying ejection velocity of ultra-relativistic material, which has an intermediate quiescent period of about 200 seconds and a variability timescale of $\sim1$~s. We consider baryonic loadings of 3 and 30 that are compatible with the hypothesis that the highest-energetic LHAASO photons might come from UHECR interactions with the extragalactic background light, and the paradigm that energetic GRBs may power the UHECR flux. For these values and the high dissipation radii considered we find consistency with the non-observation of neutrinos and no significant signatures on the electromagnetic spectrum. Inverse Compton-dominated scenarios from the prompt emission are demonstrated to lead to about an order of magnitude higher fluxes in the HE-range; this enhancement is testable by its spectral impact in the Fermi-GBM and LAT ranges.