Correlation Between Hard X-Ray and Cosmic Neutrino Sources: From Obscured AGN to Blazars

Journal article, 2026

The origin of high-energy astrophysical neutrinos remains a key open question in multimessenger astrophysics. A correlation between unabsorbed hard X-ray and high-energy neutrino luminosity has been reported in six active galactic nuclei with the highest individual IceCube significances, linking neutrino production to compact, photon-rich environments near supermassive black holes. We study whether the threshold-near IceCube excesses associated with seven Nuclear Spectroscopic Telescope Array-observed blazars are statistically consistent with that relation. Calibrating the LhX-L nu relation on the six published sources via a Bayesian regression with errors on both axes, the slope is consistent with beta = 1 and the intrinsic scatter is similar to 0.6 dex. All seven new blazars are posterior-predictively consistent with this calibration ( chi 72=1.58 , p = 0.98) under the working hypothesis that the published IceCube ns values reflect the signal. A null-injection test confirms that, at the present calibration sample size, the consistency test does not by itself adjudicate between signal and selected-background origins. A distance-free LhX/L nu ratio diagnostic places both populations within the photohadronic prediction band, statistically indistinguishable. Two diagnostics that control the common dL2 distance bias, a redshift-partial rank correlation (tau divided by z = 0.69, similar to 2.7 sigma) and a flux-space permutation test on the 13-source joint sample (p = 6.3 & times; 10-4, 3.23 sigma), indicate a residual LhX-L nu association beyond the distance-induced trend. We interpret these results as a conditional consistency check; a detection-level statement requires either an enlarged calibration set or an X-ray-weighted IceCube stacking likelihood with internal data.