The Lag-Luminosity Relation in the GRB Source-Frame: An Investigation with Swift BAT Bursts

TL;DR

This study analyzes the correlation between spectral lag and peak luminosity in GRBs using source-frame data, revealing a stronger relationship than previous observer-frame analyses, and also finds an anti-correlation with peak energy.

Contribution

It presents the first source-frame lag-luminosity relation for GRBs, demonstrating a higher correlation and refining the understanding of GRB spectral properties.

Findings

Strong correlation (−0.82) between lag and luminosity in source-frame.

Power-law index of −1.2 for the lag-luminosity relation.

Anti-correlation between source-frame lag and peak energy.

Abstract

Spectral lag, which is defined as the difference in time of arrival of high and low energy photons, is a common feature in Gamma-ray Bursts (GRBs). Previous investigations have shown a correlation between this lag and the isotropic peak luminosity for long duration bursts. However, most of the previous investigations used lags extracted in the observer-frame only. In this work (based on a sample of 43 Swift long GRBs with known redshifts), we present an analysis of the lag-luminosity relation in the GRB source-frame. Our analysis indicates a higher degree of correlation -0.82 +/- 0.05 (chance probability of ~ 5.5 x 10^-5) between the spectral lag and the isotropic peak luminosity, Liso, with a best-fit power-law index of -1.2 +/- 0.2, such that Liso proportional to lag^-1.2. In addition, there is an anti-correlation between the source-frame spectral lag and the source-frame peak energy of the burst spectrum, E_pk(1+z).