Constraining gamma-ray burst parameters with the first ultra-high energy neutrino event KM3-230213A

Abstract: Context: The detection of the highest energy neutrino observed to date by KM3NeT, with an estimated energy of 220 PeV, opens up new possibilities for the study and identification of the astrophysical sources responsible for a diffuse flux of such ultra-high-energy neutrinos, among which gamma-ray bursts are longstanding candidates. Aims: Based on the event KM3-230213A, we derive constraints on the baryon loading and density of the surrounding environment in models of blastwaves in long-duration gamma-ray bursts. Methods: We compute the diffuse flux from gamma-ray burst blastwaves, either expanding in a constant density interstellar medium or developing in a radially decreasing density of a wind-like environment surrounding the gamma-ray burst progenitor star, by taking into account the expected neutrino spectra and luminosity function. We use a Poisson likelihood method to constrain the blastwave model parameters by calculating the expected number of neutrino events within the 90% confidence level energy range of KM3-230213A and by using the joint exposure of KM3NeT/ARCA, IceCube and Pierre Auger. Results: We constrain the baryon loading to be $\leq {392, 131, 39, 13}$ at 90% confidence level, which is inversely proportional to a varying interstellar medium particle density of ${1, 3, 10, 30}$ cm$^{-3}$. In the wind-like environment case, the baryon loading is $\leq {20, 50, 100}$ at 90% confidence level, which is proportional to the sixth power of a varying density parameter of ${0.05, 0.06, 0.07}$.