2025ApJ...990L..54L

Gamma-ray bursts (GRBs) are traditionally classified into long (lGRBs) and short durations based on their T₉₀, with lGRBs widely used as tracers of the cosmic star formation rate (SFR) due to their observed association with core-collapse supernovae (SNe). However, recent detections of kilonovae accompanying some lGRBs challenge this assumption, suggesting potential contamination from compact binary mergers. Here, we move beyond the conventional T₉₀-based classification and focus exclusively on GRBs directly associated with SNe-the most direct signatures of massive stellar collapse-to reassess their connection to the SFR. Using a sample of SN/GRBs, we construct the luminosity-redshift (L-z) plane and uncover a significant correlation between these variables. To account for observational biases, we apply the τ statistic and Lynden-Bell's C^– method to derive the intrinsic luminosity function and formation rate. Our analysis reveals that even among this well-defined subsample, the SN/GRB formation rate still exceeds the SFR at low redshifts (z < 1). These findings suggest that GRBs at low redshift may not serve as reliable tracers of the SFR, and that larger samples are required to further investigate this discrepancy.