Reassessing high-energy emission correlations in gamma-ray bursts using a large, homogeneous sample of X-ray afterglows

Abstract

Gamma-ray bursts (GRBs) show diverse X-ray afterglow light-curves, including breaks and plateaus, whose physical origins remain debated. Previous claims linked high-energy ($E \ge 100$ MeV) detection to X-ray afterglow complexity or plateau incidence, but they were often based on small or heterogeneous samples. We present a large-scale, uniform, model-independent analysis of the complete Swift-XRT GRB afterglow catalog, including more than 1400 events. Our automated pipeline performs flare removal and segmented power-law fitting consistently across the sample. We find that both light-curve complexity and plateau incidence are strongly governed by the XRT observation start time, $t_{XRT}$. Apparent correlations between high-energy emission and X-ray morphology arise when $t_{XRT}$ is ignored, but vanish when the sample is stratified or controlled for this variable. X-ray complexity and plateaus are therefore not directly coupled to high-energy detectability, and early X-ray morphology is not predictive of high-energy emission. These results resolve conflicting claims in the literature and show that controlling for $t_{XRT}$ is essential in large-sample GRB studies. The automated pipeline provides a reproducible basis for future analyses of GRB afterglows from Swift and upcoming missions such as SVOM, Einstein Probe, and THESEUS.