Average power density spectrum of long GRBs detected with BeppoSAX/GRBM and with Fermi/GBM

TL;DR

This study analyzes the average power density spectrum of long GRBs detected by BeppoSAX/GRBM and Fermi/GBM, revealing a high-frequency break and confirming the energy dependence of the PDS slope across different instruments and energy ranges.

Contribution

It provides the first high-frequency PDS analysis up to 1 kHz with BeppoSAX/GRBM and broad energy range analysis with Fermi/GBM, extending previous findings.

Findings

Identified a break around 1-2 Hz in the PDS at high frequencies.

Confirmed that harder photons have shallower PDS slopes.

Extended the energy dependence of PDS slope across different instruments.

Abstract

From past experiments the average power density spectrum (PDS) of GRBs with unknown redshift was found to be modelled from 0.01 to 1 Hz with a power-law, f^(-alpha), with alpha broadly consistent with 5/3. Recent analyses of the Swift/BAT catalogue showed analogous results in the 15-150 keV band. We carried out the same analysis on the bright GRBs detected by BeppoSAX/GRBM and Fermi/GBM. The BeppoSAX/GRBM data, in the energy range 40-700 keV and with 7.8 and 0.5-ms time resolutions, allowed us to explore for the first time the average PDS at very high frequencies (up to 1 kHz) and reveal a break around 1-2 Hz, previously found in CGRO/BATSE data. The Fermi/GBM data, in the energy band 8-1000 keV, allowed us to explore for the first time the average PDS within a broad energy range. Our results confirm and extend the energy dependence of the PDS slope, according to which harder photons have shallower PDS.