Comprehension of Jet Physics from the Analysis of the Gamma-Ray Burst Afterglow Parameter Distributions |
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Authors: | Alessandra Berretta Paolo Cristarella Orestano Sara Cutini Stefano Germani Isabella Mereu Michele Punturo Gino Tosti |
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Institution: | 1. Dipartimento di Fisica e Geologia, Universitá degli Studi di Perugia, Via Alessandro Pascoli, s.n.c., Perugia, PG, 06123 Italia;2. Istituto Nazionale di Fisica Nucleare, Sezione di Perugia and Università degli Studi di Perugia, Via Alessandro Pascoli, 23c, Perugia, PG, 06123 Italia |
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Abstract: | The discovery of a short gamma-ray burst (GRB), GRB170817A, in association with a gravitational wave (GW) and a bright kilonova started a new era in the high-energy astrophysics. The observation of GRB170817A and more recently, GRB200826A and GRB211211A, a short and a long burst, respectively, with a possible kilonova, reinforce the concern about new ways of classification. For this reason, a new machine learning technique is applied to Swift-BAT data, searching for morphological similarities in the light curves. The resulting map is characterized by two distinct groups, although still correlated with standard T90 duration. Since a jet viewed off-axis could explain the emission from GRB170817A, the modeling of this kind of sources is of great importance. A public code called JetFit, based on the “boosted fireball” model, is applied to fit Swift-XRT afterglow light curves of short and long GRBs, with known red-shift, from 2005 to 2021. JetFit does not model the flaring activity. For this purpose, a new technique to remove the time flaring phases, is developed. This analysis provides a comprehensive study of the prompt and of the afterglow phase, trough the study of the best-fit parameters. |
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Keywords: | gamma-ray burst afterglow gamma-ray bursts gamma-ray burst prompts jet physics |
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