Transients stemming from collapsing massive stars: The missing pieces to advance joint observations of photons and high-energy neutrinos

Collapsing massive stars lead to a broad range of astrophysical transients, whose multi-wavelength emission is powered by a variety of processes including radioactive decay, activity of the central engine, and interaction of the outflows with a dense circumstellar medium. These transients are also candidate factories of neutrinos with energy up to hundreds of PeV. We review the energy released by such astrophysical objects across the electromagnetic wavebands as well as neutrinos, in order to outline a strategy to optimize multi-messenger follow-up programs. We find that, while a significant fraction of the explosion energy can be emitted in the infrared-optical-ultraviolet (UVOIR) band, the optical signal alone is not optimal for neutrino searches. Rather, the neutrino emission is strongly correlated with the one in the radio band, if a dense circumstellar medium surrounds the transient, and with X-rays tracking the activity of the central engine. Joint observations of transients in radio, X-rays, and neutrinos will crucially complement those in the UVOIR band, breaking degeneracies in the transient parameter space. Our findings call for heightened surveys in the radio and X-ray bands to warrant multi-messenger detections.