Unveiling Multimessenger Emission from Hidden Cores of Microquasars

TL;DR

This paper models multimessenger emissions from microquasars' hidden cores, explaining observed gamma rays and predicting variability and neutrino fluxes, advancing understanding of cosmic-ray acceleration in these systems.

Contribution

It introduces a comprehensive simulation approach for microquasar emissions considering different regions, providing new predictions for gamma-ray spectra, variability, and neutrino fluxes based on physical conditions.

Findings

Observed >TeV gamma rays can originate from pγ or pp interactions.

Models predict spectral features like dips or suppression in 0.1-10 TeV range.

Neutrino fluxes are significantly suppressed, challenging detection.

Abstract

Microquasars are radio-emitting X-ray binaries accompanied by relativistic jets. They are established sources of 100~TeV gamma rays and are considered promising candidates for cosmic-ray acceleration. Motivated by recent detections of $\sim 100~$TeV photons from Cygnus~X-1 and $\sim~$PeV photons from Cygnus~X-3 by the Large High Altitude Air Shower Observatory (LHAASO), we employ the Astrophysical Multimessenger Emission Simulator (AMES) to model their multimessenger emission considering compact outflow regions as cosmic-ray accelerators, spanning from radio to ultra-high-energy gamma rays. Our results show that the observed $>$TeV gamma rays can originate from either $p\gamma$ or $pp$ interactions, depending on the location and physical conditions of the emission region, while also reproducing the lower-energy spectra. The different configurations yield unique, observationally testable predictions. In the $0.1-10$~TeV energy range, where current observations provide only upper limits, they predict either a deep dip, a mild suppression, or a power-law spectrum. Additionally, models involving AU-scale blob regions predict strong variability, while those invoking more extended and static external zones show more stable behavior. We also provide a possible qualitative explanation for the distinct modulation patterns across different energy bands, which relies primarily on changes in the Doppler factor and external $\gamma\gamma$ absorption. Finally, our neutrino predictions, which properly account for muon and pion cooling effects, reveal a significantly suppressed flux, indicating that detecting these sources may be more challenging than previously anticipated.