High-Energy Neutrinos from Gamma-Ray-Faint Accretion-Powered Hypernebulae

Abstract

Hypernebulae are inflated by accretion-powered winds accompanying hyper-Eddington mass transfer from an evolved post-main sequence star onto a black hole or neutron star companion. The ions accelerated at the termination shock -- where the collimated fast disk winds/jet collide with the slower, wide-angled wind-fed shell -- can generate high-energy neutrinos via hadronic ($pp$) reactions, and photohadronic ($p\gamma$) interactions with the disk thermal and Comptonized nonthermal background photons. It has been suggested that some fast radio bursts (FRBs) may be powered by such short-lived jetted hyper-accreting engines. Although neutrino emission associated with the ms-duration bursts themselves is challenging to detect, the persistent radio counterparts of some FRB sources -- if associated with hypernebulae -- could contribute to the high energy neutrino diffuse background flux. If the hypernebula birth rate follows that of steller-merger transients and common envelope events, we find that their volume-integrated neutrino emission -- depending on the population-averaged mass-transfer rates -- could explain up to $\sim25\%$ of the high-energy diffuse neutrino flux observed by the IceCube Observatory and the Baikal-Gigaton Volume Detector (GVD) Telescope. The time-averaged neutrino spectrum from hypernebula -- depending on the population parameters -- can also reproduce the observed diffuse neutrino spectrum. The neutrino emission could in some cases furthermore extend to >100 PeV, detectable by future ultra-high-energy neutrino observatories. The large optical depth through the nebula to Breit-Wheeler ($\gamma\gamma$) interaction attenuates the escape of GeV-PeV gamma-rays co-produced with the neutrinos, rendering these gamma-ray-faint neutrino sources, consistent with the \textit{Fermi} observations of the isotropic gamma-ray background.