Study of GRB light curve decay indices in the afterglow phase

Abstract

In this work we study the distribution of temporal power-law decay indices, $\alpha$, in the Gamma Ray Burst (GRB) afterglow phase, fitted for $176$ GRBs (139 long GRBs, 12 short GRBs {\it with extended emission} and 25 X-Ray Flashes (XRFs)) with known redshifts. These indices are compared with the temporal decay index, ${\alpha }_W$, derived with the light curve fitting using the \cite{willingale07} model. This model fitting yields similar distributions of ${\alpha }_W$ to the fitted $\alpha$, but for individual bursts a difference can be significant. Analysis of ($\alpha$, $L_a$) distribution, where $L_a$ is the characteristic luminosity at the end of the plateau, reveals only a weak correlation of these quantities. However, we discovered a significant regular trend when studying GRB $\alpha$ values along the \cite{dainotti2008} correlation between $L_a$ and the end time of the plateau emission in the rest frame, $T_a^{\ast }$, hereafter LT correlation. We note a systematic variation of the $\alpha$ parameter distribution with luminosity for any selected $T_a^{\ast }$. We analyze this systematics with respect to the fitted LT correlation line, expecting that the presented trend may allow to constrain the GRB physical models. We also attempted to use the derived correlation of $\alpha (T_a)$ versus $L_a(T_a)$ to diminish the luminosity scatter related to the variations of $\alpha$ along the LT distribution, a step forward in the effort of standardizing GRBs. A proposed toy model accounting for this systematics applied to the analyzed GRB distribution results in a slight increase of the LT correlation coefficient.

Accepted for publication in ApJ

References in corpus (11)

• A time - luminosity correlation for Gamma Ray Bursts in the X - rays
• Can the early X-ray afterglow of GRBs be explained by a contribution from the reverse shock?
• Constraining properties of GRB magnetar central engines using the observed plateau luminosity and duration correlation
• Properties of Gamma-Ray Burst Progenitor Stars
• A New Paradigm for Gamma Ray Bursts: Long Term Accretion Rate Modulation by an External Accretion Disk
• Prior Emission Model for X-ray Plateau Phase of Gamma-Ray Burst Afterglows
• Study of possible systematics in the L*X - Ta* correlation of Gamma Ray Bursts
• Evidence of Exponential Decay Emission in the Swift Gamma-ray Bursts
• Selection effects in Gamma Ray Bursts correlations: consequences on the ratio between GRB and star formation rates
• Gamma-ray burst afterglow plateau break time - luminosity correlations favour thick shell models over thin shell models
• X-ray afterglow light curves : toward standard candle ?

Cited by in corpus (21)

• On the evolution of the Hubble constant with the SNe Ia Pantheon Sample and Baryon Acoustic Oscillations: a feasibility study for GRB-cosmology in 2030
• On the magnetar origin of the GRBs presenting X-ray afterglow plateaus
• The X-ray fundamental plane of the Platinum Sample, the Kilonovae and the SNe Ib/c associated with GRBs
• A study of gamma ray bursts with afterglow plateau phases associated with supernovae
• Optical and X-ray GRB Fundamental Planes as Cosmological Distance Indicators
• Fast-transient Searches in Real Time with ZTFReST: Identification of Three Optically-discovered Gamma-ray Burst Afterglows and New Constraints on the Kilonova Rate
• A Study of the Gamma-Ray Burst Fundamental Plane
• Gamma Ray Burst afterglow and prompt-afterglow relations: an overview
• The Gamma-ray Bursts fundamental plane correlation as a cosmological tool
• Standardized long gamma-ray bursts as a cosmic distance indicator
• On the investigation of the closure relations for Gamma-Ray Bursts observed by Swift in the post-plateau phase and the GRB fundamental plane
• On the Existence of the Plateau Emission in High-Energy Gamma-Ray Burst LightCurves observed byFermi-LAT
• X-ray Plateaus in Gamma-Ray Burst Afterglows and Their Application in Cosmology
• Closure relations during the plateau emission of Swift GRBs and the fundamental plane
• Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies
• GRB 180418A: A possibly-short GRB with a wide-angle outflow in a faint host galaxy
• The closure relations in optical afterglow of Gamma-Ray Bursts
• GRB 191016A: A Long Gamma-Ray Burst Detected by TESS
• Measuring cosmic dipole with the GRB luminosity-time relation
• Similar Fermi-GBM sGRBs to GW/sGRB 170817A in MeV-GeV energies
• Gamma-Ray Bursts, Supernovae Ia and Baryon Acoustic Oscillations: a binned cosmological analysis