Hints for families of GRBs improving the Hubble diagram

Abstract

As soon as their extragalactic origins were established, the hope to make Gamma - Ray Bursts (GRBs) standardizeable candles to probe the very high - z universe has opened the search for scaling relations between redshift independent observable quantities and distance dependent ones. Although some remarkable success has been achieved, the empirical correlations thus found are still affected by a significant intrinsic scatter which downgrades the precision in the inferred GRBs Hubble diagram. We investigate here whether this scatter may come from fitting together objects belonging to intrinsically different classes. To this end, we rely on a cladistics analysis to partition GRBs in homogenous families according to their rest frame properties. Although the poor statistics prevent us from drawing a definitive answer, we find that both the intrinsic scatter and the coefficients of the $E_{peak}$\,-\,$E_{iso}$ and $E_{peak}$\,-\,$L$ correlations significantly change depending on which subsample is fitted. It turns out that the fit to the full sample leads to a scaling relation which approximately follows the diagonal of the region delimited by the fits to each homogenous class. We therefore argue that a preliminary identification of the class a GRB belongs to is necessary in order to select the right scaling relation to be used in order to not bias the distance determination and hence the Hubble diagram.

10 pages, 6 figures, 4 tables, accepted for publication on MNRAS

References in corpus (8)

• Measuring the cosmological parameters with the Ep,i-Eiso correlation of Gamma-Ray Bursts
• The Hubble Diagram to Redshift >6 from 69 Gamma-Ray Bursts
• The Second Swift BAT Gamma-Ray Burst Catalog
• An updated Gamma Ray Bursts Hubble diagram
• Statistical Evidence for Three classes of Gamma-ray Bursts
• The environment of formation as a second parameter for globular cluster classification
• A six-parameter space to describe galaxy diversification
• Towards a Phylogenetic Analysis of Galaxy Evolution : a Case Study with the Dwarf Galaxies of the Local Group

Cited by in corpus (6)

• Multivariate Approaches to Classification in Extragalactic Astronomy
• Cladistical analysis of the Jovian and Saturnian satellite systems
• Phylogenetic Analyses of Quasars and Galaxies
• Astrocladistics of the Jovian Trojan Swarms
• Concepts of Classification and Taxonomy. Phylogenetic Classification
• Phylogenetic Tools in Astrophysics