Multimessenger Modeling of Low-luminosity γ -Ray Bursts

Abstract Low-luminosity γ -ray bursts (LL GRBs), a subclass of the most powerful transients in the Universe, remain promising sources of high-energy astrophysical neutrinos, despite strong IceCube constraints on typical long GRBs. In this work, a novel approach is introduced to study a sample of seven LL GRBs with their multiwavelength observations to investigate leptohadronic processes during their prompt emission phases. The relative energy densities in magnetic fields, nonthermal electrons, and protons are constrained, with the latter defining the cosmic-ray (CR) loading factor. Our results suggest that LL GRBs exhibit diverse emission processes, as confirmed by a machine learning analysis of the fitted parameters. Across the seven LL GRBs, we find the posterior medians of the CR loading factor to be in the range of ξ p ∼ 0.2–1.6. GRB 060218 and GRB 100316D, the lowest-luminosity bursts ( L γ ,iso ∼ 10 46 –10 47 erg s −1 ) consistent with the shock-breakout scenario, yield the highest CR loading factors and therefore are expected to produce neutrinos more efficiently. Our model predicts the expected number of neutrino signals that are consistent with current limits but would be detectable with next-generation neutrino observatories. These results strengthen the case for LL GRBs as promising sources of high-energy astrophysical neutrinos and motivate real-time searches for coincident LL GRB and neutrino events. Next-generation X-ray and MeV facilities will be critical for identifying more LL GRBs and strengthening their role in multimessenger astrophysics.