# Detection of Low-Redshift Excess in Supernova-Linked Gamma-Ray Bursts

**Authors:** Qin-Mei Li, Qi-Bin Sun, Sheng-Bang Qian, Fu-Xing Li  
**arXiv:** [2507.13603](https://arxiv.org/abs/2507.13603)  
**Date:** 2025-07-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2507.13603v1/

## Key points

- Study focuses on gamma-ray bursts (GRBs) associated with supernovae as markers of massive stellar collapse
- Notable correlation between luminosity and redshift observed in SN/GRBs sample
- Shift from traditional classification based on $T_{90}$ values to focus on GRBs directly linked to supernovae
- Use of statistical methods like $\tau$ statistic and Lynden-Bell's $C^{-}$ method to derive intrinsic luminosity function and formation rate within SN/GRB subset
- Formation rate of SN/GRBs exceeds star formation rate at low redshifts, challenging previous assumptions
- Emphasis on need for larger sample sizes to further investigate discrepancies and understand relationship between GRBs and cosmic star formation rates.

## Summary

In their study titled "Detection of Low-Redshift Excess in Supernova-Linked Gamma-Ray Bursts," authors Qin-Mei Li, Qi-Bin Sun, Sheng-Bang Qian, and Fu-Xing Li delve into the classification and implications of gamma-ray bursts (GRBs) associated with supernovae. The researchers focus on GRBs directly linked to supernovae - which serve as direct markers of massive stellar collapse. By analyzing a sample of SN/GRBs, they construct a luminosity-redshift ($L$-$z$) plane and uncover a notable correlation between these two variables. This research sheds new light on the complexities surrounding GRB classifications and their implications for our understanding of stellar evolution and cosmic phenomena. The traditional categorization of GRBs into long (lGRBs) and short (sGRBs) durations based on their $T_{90}$ values has been used to indicate the cosmic star formation rate (SFR), with lGRBs often connected to core-collapse supernovae. However, recent observations of kilonovae accompanying some lGRBs have raised questions about this association, hinting at potential contamination from compact binary mergers. To address these uncertainties, the researchers shift focus from the conventional $T_{90}$-based classification to specifically examine GRBs directly linked to supernovae. To mitigate observational biases, the authors employ statistical methods such as the $\tau$ statistic and Lynden-Bell's $C^{-}$ method to derive the intrinsic luminosity function and formation rate within this well-defined subset of SN/GRBs. Surprisingly, even within this subset, the formation rate exceeds the SFR at low redshifts ($z < 1). These findings suggest that GRBs at lower redshifts may not be reliable indicators of the SFR as previously assumed. The authors emphasize the need for larger sample sizes to further investigate this discrepancy and gain a more comprehensive understanding of the relationship between GRBs and cosmic star formation rates.