Neutrinos from hidden ultraluminous X-ray sources in the Galaxy

Abstract

Ultraluminous X-ray sources (ULXs) are point-like sources that exhibit apparent X-ray luminosities exceeding the Eddington limit for stellar-mass compact objects. A widely accepted interpretation is that these systems are X-ray binaries accreting matter possibly at super-Eddington rates. In this regime, photon trapping inflates the accretion disk, making it geometrically and optically thick. Radiation-driven winds launched from the supercritical disk form funnel-shaped walls along the symmetry axis. While the apparent X-ray luminosity can exceed the Eddington limit due to geometrical beaming within this funnel, a misalignment with the observer's line of sight strongly suppresses the X-ray emission, rendering the ULX electromagnetically obscured. This work explores the potential for high-energy neutrino production in black hole-hosting ULXs. We model proton acceleration via magnetic reconnection in the region above the super-accreting black hole. Although electromagnetic emission is efficiently absorbed by the dense wind and radiation fields, neutrinos generated from photomeson interactions can escape. Our model self-consistently accounts for energy losses of pions and muons in this environment. The results indicate that misaligned, electromagnetically obscured Galactic ULXs could produce a neutrino flux detectable by instruments like KM3NeT and IceCube within several years of observation.