Multi-messenger blazar modeling: recent developments and open questions

Abstract: In this talk I share recent results from leptohadronic modeling of 32 BL Lac objects coincident with IceCube high-energy neutrino alert events. Using a newly released open-source cosmic-ray simulation software, we have built a robust physical framework that can simultaneously describe multi-wavelength observations and IceCube point source data. This provides new constraints on the source environment, including the position of the gamma-ray emitting region and the elusive role of broad line emission in masquerading BL Lacs. I discuss future paths for tackling open questions on time-domain hadronic signatures, IceCube data interpretation, and cosmic ray acceleration.