LeHaMoC: A versatile time-dependent lepto-hadronic modeling code for high-energy astrophysical sources

Abstract

Context. Recent associations of high-energy neutrinos with active galactic nuclei (AGN) have revived the interest in leptohadronic models of radiation from astrophysical sources. The rapid increase in the amount of acquired multi-messenger data will require fast numerical models that may be applied to large source samples. Aims. We develop a time-dependent leptohadronic code, LeHaMoC, that offers several notable benefits compared to other existing codes, such as versatility and speed. Methods. LeHaMoC solves the Fokker-Planck equations of photons and relativistic particles (i.e. electrons, positrons, protons, and neutrinos) produced in a homogeneous magnetized source that may also be expanding. The code utilizes a fully implicit difference scheme that allows fast computation of steady-state and dynamically evolving physical problems. Results. We first present test cases where we compare the numerical results obtained with LeHaMoC against exact analytical solutions and numerical results computed with ATHEvA, a well-tested code of similar philosophy but a different numerical implementation. We find a good agreement (within 10–30%) with the numerical results obtained with ATHEvA without evidence of systematic differences. We then demonstrate the capabilities of the code through illustrative examples. First, we fit the spectral energy distribution from a jetted AGN in the context of a synchrotron-self Compton model and a proton-synchrotron model using Bayesian inference. Second, we compute the high-energy neutrino signal and the electromagnetic cascade induced by hadronic interactions in the corona of NGC 1068. Conclusions. LeHaMoC is easily customized to model a variety of high-energy astrophysical sources and has the potential to become a widely utilized tool in multi-messenger astrophysics.