Measuring cosmic dipole with the GRB luminosity-time relation

Abstract

We present a new analysis of cosmic dipole anisotropy using gamma-ray bursts (GRBs) as high-redshift standardizable candles. GRBs are ideal probes for testing the cosmological principle thanks to their high luminosity, wide redshift range, and nearly isotropic sky coverage. For the first time, we employ the luminosity-time (L-T) relation, known in the literature as the bidimensional X-ray Dainotti relation, corrected for redshift evolution, to standardize a sample of 176 long GRBs detected by \textit{Swift}. We test for dipolar modulations in the GRB Hubble diagram using both the Dipole Fit Method and a new approach introduced here, the Anisotropic Residual Analysis Method. Both methods yield consistent results: a dipole amplitude of $A_d\simeq 0.6\pm 0.2$ pointing towards (RA, DEC) $\approx (134^{\circ }\pm 30^{\circ },-36^{\circ }\pm 21^{\circ })$ (equatorial coordinates). As shown in the Appendix, this corresponds to a boost velocity of the observer with respect to the GRB rest-frame in the antipodal direction from the dipole direction. Extensive isotropy tests and 20,000 Monte Carlo simulations confirm that the detected signal cannot be explained by chance alignments or by the angular distribution of the GRB sample. We also show how, by incorporating a dipole term, residual correlations are eliminated, showing that the dipole model provides a better fit than standard isotropic $\Lambda$CDM.

JHEAP accepeted version. 16 pages, 14 Figures

References in corpus (42)

• emcee: The MCMC Hammer
• Challenges for $\Lambda$CDM: An update
• GRB Formation Rates inferred from the Spectral Peak Energy - Luminosity Relation
• The Ep,i - Eiso correlation in GRBs: updated observational status, re-analysis and main implications
• On the Hubble constant tension in the SNe Ia Pantheon sample
• A Test of the Cosmological Principle with Quasars
• A time - luminosity correlation for Gamma Ray Bursts in the X - rays
• Evidence for anisotropy of cosmic acceleration
• Probing the anisotropic local universe and beyond with SNe Ia data
• Cosmic radio dipole from NVSS and WENSS
• Large peculiar motion of the solar system from the dipole anisotropy in sky brightness due to distant radio sources
• A Challenge to the Standard Cosmological Model
• Determination of the intrinsic Luminosity Time Correlation in the X-ray Afterglows of GRBs
• High redshift radio galaxies and divergence from the CMB dipole
• Observational Challenges for the Standard FLRW Model
• Probing the Cosmological Principle in the counts of radio galaxies at different frequencies
• Cosmological implications of the anisotropy of ten galaxy cluster scaling relations
• Is there Correlation between Fine Structure and Dark Energy Cosmic Dipoles?
• Analyzing the Large-Scale Bulk Flow using CosmicFlows4: Increasing Tension with the Standard Cosmological Model
• Hints of FLRW Breakdown from Supernovae
• The Cosmic Radio Dipole: Estimators and Frequency Dependence
• The X-ray fundamental plane of the Platinum Sample, the Kilonovae and the SNe Ib/c associated with GRBs
• Slope evolution of GRB correlations and cosmology
• Anomalies in Physical Cosmology
• Testing homogeneity on large scales in the Sloan Digital Sky Survey Data Release One
• The Gamma-ray Bursts fundamental plane correlation as a cosmological tool
• A 14 $h^{-3}$ Gpc${}^3$ study of cosmic homogeneity using BOSS DR12 quasar sample
• Probing the anisotropic expansion from supernovae and GRBs in a model-independent way
• Testing the Cosmological Principle with CatWISE Quasars: A Bayesian Analysis of the Number-Count Dipole
• On the investigation of the closure relations for Gamma-Ray Bursts observed by Swift in the post-plateau phase and the GRB fundamental plane
• Very large scale correlations in the galaxy distribution
• The cosmic radio dipole: Bayesian estimators on new and old radio surveys
• Testing Isotropic Universe Using the Gamma-Ray Burst Data of Fermi / GBM
• Study of GRB light curve decay indices in the afterglow phase
• Update on Testing the Isotropy of the Properties of Gamma-Ray Bursts
• Covariant cosmography: the observer-dependence of the Hubble parameter
• Easily Interpretable Bulk Flows: Continuing Tension with the Standard Cosmological Model
• Testing cosmic anisotropy with Pade approximation and Pantheon+ sample
• Anisotropy in Pantheon+ supernovae
• Cosmography of the Local Universe by Multipole Analysis of the Expansion Rate Fluctuation Field
• Cosmic Flow Measurement and Mock Sampling Algorithm of Cosmicflows-4 Tully-Fisher Catalogue
• Dipolar fluence distribution of statistically isotropic FERMI gamma-ray bursts