Speaker
Description
Since the start of operations, the IceCube Observatory has been characterizing the background flux of high-energy astrophysical neutrinos. However, only a fraction of this flux has been associated with known source populations. One of the most plausible production mechanisms for these neutrinos is photohadronic (pγ) interaction. In this scenario, the energies of PeV cosmic rays and sub-PeV neutrinos naturally point to X-ray-rich environments, such as gamma-ray bursts and tidal disruption events, as promising source candidates. We performed a follow-up search for X-ray counterparts to public IceCube Gold and Bronze neutrino alerts using approximately two years of observations from the Wide-field X-ray Telescope (WXT) aboard the Einstein Probe (EP). Thanks to its unprecedented combination of a large field of view and high sensitivity, EP/WXT enables searches for X-ray counterparts at distances beyond those accessible to previous measurements. Even in the absence of a significant counterpart detection, the observations place constraints on the fraction of cosmic-ray energy injected into the radiation field (the cosmic-ray loading factor). In this talk, we present the results of this analysis for the first time and discuss their implications for the cosmic ray origin.
