Lunch talk on Jun. 24, 2026
Unveiling Multimessenger Emission from Hidden Cores of Microquasars
Speaker: Yu-Jia Wei (Pennsylvania State University)
Venue: SWIFAR Building 2111
Time: 12:45 PM, Wednesday, Jun. 24, 2026
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 approximately 100 TeV photons from Cygnus X-1 and multi-PeV photons from Cygnus X-3 by the Large High Altitude Air Shower Observatory, we employ the Astrophysical Multimessenger Emission Simulator to model their multimessenger emission, considering compact outflow regions as cosmic-ray accelerators and covering emission from radio to ultrahigh-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. These different configurations of emission regions yield unique, observationally testable predictions. In the 0.1–10 TeV energy range, where current observations provide only upper limits, the models predict either a deep dip, 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 distinct modulation patterns across different energy bands, which relies primarily on changes in the Doppler factor and external \gamma\gamma absorption. In particular, we find that 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, 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.
