The dispersion of $E_{\mathrm{p},\mathrm{i}}$-$L_{\mathrm{iso}}$ correlation of long gamma-ray bursts is partially due to assembling different sources

Abstract

Long gamma-ray burst (GRB) prompt emission shows a correlation between the intrinsic peak energy, $E_{\mathrm{p},\mathrm{i}}$, of the time-average $\nu F_{\nu }$ spectrum and the isotropic-equivalent peak gamma-ray luminosity, $L_{\mathrm{p},\mathrm{iso}}$, as well as the total released energy, $E_{\mathrm{iso}}$. The same correlation is found within individual bursts, when time-resolved $E_{\mathrm{p},\mathrm{i}}$ and $L_{\mathrm{iso}}$ are considered. These correlations are characterised by an intrinsic dispersion, whose origin is still unknown. Discovering the origin of the correlation and of its dispersion would shed light on the still poorly understood prompt emission and would propel GRBs to powerful standard candles. We studied the dispersion of both isotropic-equivalent and collimation-corrected time-resolved correlations. We also investigated whether the intrinsic dispersion computed within individual GRBs is different from that obtained including different bursts into a unique sample. We then searched for correlations between key features, like Lorentz factor and jet opening angle, and intrinsic dispersion, when the latter is treated as one of the characterising We performed a time-resolved spectral analysis of 20 long Type-II or collapsar-candidate GRBs detected by the Fermi Gamma-ray Burst Monitor with known redshift and estimates of jet opening angle and/or Lorentz factor. The collimation-corrected correlation appears to be no less dispersed than the isotropic-equivalent one. Also, individual GRBs are significantly less dispersed than the whole sample. We excluded (at $4.2\sigma$ confidence level) the difference in samples' sizes as the possible reason, thus confirming that individual GRBs are {\em intrinsically} less dispersed than the whole sample. No correlation was found between intrinsic dispersion and other key properties for the few GRBs with available information.

7 pages, 1 figure

References in corpus (14)

• The Physics of Gamma-Ray Bursts and Relativistic Jets
• A Kilonova Following a Long-Duration Gamma-Ray Burst at 350 Mpc
• A nearby long gamma-ray burst from a merger of compact objects
• A long-duration gamma-ray burst with a peculiar origin
• A Comprehensive Analysis of Fermi Gamma-ray Burst Data: II. $E_{\mathrm{p}}$-Evolution Patterns and Implications for the Observed Spectrum-Luminosity Relations
• The Ep,i - Eiso correlation: type I gamma-ray bursts and the new classification method
• Bulk Lorentz factors of Gamma-Ray Bursts
• The Fermi GBM Gamma-Ray Burst Spectral Catalog: 10 Years of Data
• The peculiar short-duration GRB 200826A and its supernova
• Structure of Gamma-Ray Burst jets: intrinsic versus apparent properties
• The SVOM Mission
• GRB minimum variability timescale with Insight-HXMT and Swift: implications for progenitor models, dissipation physics and GRB classifications
• On Spectral Evolution and Temporal Binning in Gamma-Ray Bursts
• Statistical study of gamma-ray bursts with jet break feature in multi-wavelength afterglow emissions