Unveiling Multimessenger Emission from Hidden Cores of Microquasars

Microquasars are radio-emitting X-ray binaries with relativistic jets and are established sources of ∼100 TeV gamma rays, making them promising candidates for cosmic-ray acceleration. Motivated by recent detections of ∼100 TeV photons from Cygnus X-1 and multi-PeV photons from Cygnus X-3, we employ the Astrophysical Multimessenger Emission Simulator (AMES) to model their multimessenger emission from radio to ultrahigh-energy gamma rays. Our modeling suggests that particle acceleration is extremely efficient in the jet region. The observed ≳0.1 PeV gamma rays can originate from either pγ or pp interactions, depending on the location and physical conditions of the emission region, while also reproducing the lower-energy spectra. These configurations yield observationally testable predictions. In the poorly constrained 0.1–10 TeV band, the models predict either a deep valley, a mild suppression, or a power-law spectrum. Additionally, models involving compact emission regions comparable to the orbital separation 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 energy-dependent modulation patterns, relying primarily on changes in the Doppler factor and external γγ absorption. In particular, explaining the PeV emission from Cygnus X-3 favors a compact emission region, for which a magnetic field strength of order 10 2 G is required. Finally, after accounting for pion and muon cooling, the predicted neutrino flux is suppressed, implying that detection is more challenging than previously thought.