Distribution of number of peaks within a long gamma-ray burst

Abstract

The variety of long duration gamma-ray burst (LGRB) light curves (LCs) encode a wealth of information on how LGRB engines release energy following the collapse of the progenitor star. Attempts to characterise GRB LCs focused on a number of properties, such as the minimum variability timescale, power density spectra (both ensemble average and individual), or with different definitions of variability. In parallel, a characterisation as a stochastic process was pursued by studying the distributions of waiting times, peak flux, fluence of individual peaks within GRB time profiles. Yet, the question remains as to whether the diversity of profiles can be described in terms of a common stochastic process. Here we address this issue by studying for the first time the distribution of the number of peaks in a GRB profile. We used four different GRB catalogues: CGRO/BATSE, Swift/BAT, BeppoSAX/GRBM, and Insight-HXMT. The statistically significant peaks were identified by means of well tested algorithm MEPSA and further selected by applying a set of thresholds on signal-to-noise ratio. We then extracted the corresponding distributions of number of peaks per GRB. Among the different models considered (power-law, simple or stretched exponential) only a mixture of two exponentials models all the observed distributions, suggesting the existence of two distinct behaviours: (i) an average number of 2.1+-0.1 peaks per GRB ("peak poor") and accounting for about 80% of the observed population of GRBs; (ii) an average number of 8.3+-1.0 peaks per GRB ("peak rich") and accounting for the remaining 20% of the observed population. We associate the class of peak-rich GRBs with the presence of sub-second variability, which seems to be absent among peak-poor GRBs. The two classes could result from two different regimes through which GRB engines release energy or through which energy is dissipated into gamma-rays.

7 pages, 5 figures, accepted by A&A

References in corpus (17)

• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• The Physics of Gamma-Ray Bursts and Relativistic Jets
• The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
• A nearby long gamma-ray burst from a merger of compact objects
• A long-duration gamma-ray burst with a peculiar origin
• JWST detection of heavy neutron capture elements in a compact object merger
• The Konus-Wind catalog of gamma-ray bursts with known redshifts. I. Bursts detected in the triggered mode
• Astrophysics: A burst of new ideas
• The case for a minute-long merger-driven gamma-ray burst from fast-cooling synchrotron emission
• The structure of weakly-magnetized $\gamma$-ray burst jets
• The Gamma--Ray Burst catalog obtained with the Gamma Ray Burst Monitor aboard BeppoSAX
• The Konus-Wind catalog of gamma-ray bursts with known redshifts. II. Waiting mode bursts simultaneously detected by Swift/BAT
• GRB minimum variability timescale with Insight-HXMT and Swift: implications for progenitor models, dissipation physics and GRB classifications
• The slope of the GRB Variability/Peak Luminosity Correlation
• Intermittent mildly magnetized jets as the source of GRBs
• The First Insight-HXMT Gamma-Ray Burst Catalog: The First Four Years
• Variabilities of Gamma-ray Bursts from Black Hole Hyper-accretion Disks

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• New results on the gamma-ray burst variability-luminosity relation
• Long gamma-ray burst light curves as the result of a common stochastic pulse-avalanche process
• GRB minimum variability timescales with Fermi/GBM
• A search for periodic activity in multi-peaked long gamma-ray bursts
• FAST-MEPSA: an optimised and faster version of peak detection algorithm MEPSA