arXiv subjects

Pascal Chardonnet

Publications and source records attributed to Pascal Chardonnet.

21 records · Page 2Linked to original sources

arXiv2004

GRB 980425, SN1998bw and the EMBH model

The EMBH model, previously developed using GRB 991216 as a prototype, is here applied to GRB 980425. We fit the luminosity observed in the 40-700 keV, 2-26 keV and 2-10 keV bands by the BeppoSAX satellite. In addition we present a novel scenario in which the supernova SN1998bw is the outcome of an ``induced gravitational collapse'' triggered by GRB 980425, in agreement with the GRB-Supernova Time Sequence (GSTS) paradigm (Ruffini et al. 2001c). A further outcome of this astrophysically exceptional sequence of events is the formation of a young neutron star generated by the SN1998bw event. A coordinated observational activity is recommended to further enlighten the underlying scenario of this most unique astrophysical system.

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arXiv2004

Emergence of a filamentary structure in the fireball from GRB spectra

It is shown that the concept of a fireball with a definite filamentary structure naturally emerges from the analysis of the spectra of Gamma-Ray Bursts (GRBs). These results, made possible by the recently obtained analytic expressions of the equitemporal surfaces in the GRB afterglow, depend crucially on the single parameter R describing the effective area of the fireball emitting the X- and gamma ray radiation. The X- and gamma ray components of the afterglow radiation are shown to have a thermal spectrum in the co-moving frame of the fireball and originate from a stable shock front described self-consistently by the Rankine-Hugoniot equations. Precise predictions are presented on a correlations between spectral changes and intensity variations in the prompt radiation verifiable, e.g., by the Swift and future missions. The highly variable optical and radio emission depends instead on the parameters of the surrounding medium. The GRB 991216 is used as a prototype for this model.

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arXiv1997

The Production of Anti-Matter in our Galaxy

The discovery of a single anti-helium nucleus in the cosmic ray flux would definitely point toward the existence of stars and even of entire galaxies made of anti-matter. The presence of anti-nuclei in cosmic rays has actually profound implications on the fundamental question of the baryon asymmetry of the universe. It is therefore crucial to determine the amount of anti-matter which our own galaxy already produces through the spallation of high-energy protons on the interstellar gas of the galactic disk. We have used here a coalescence model to assess the amount of anti-deuterium and anti-helium 3 present in cosmic rays together with anti-protons. The propagation of cosmic rays in the galaxy is described through a two-zone diffusion model which correctly describes the observed abundances. We find that the antideuterium/proton ratio exceeds $10^{-9}$ above a momentum per anti-nucleon of about 4 GeV/c. Would the universe be purely made of matter, the AMS collaboration should be able to detect a few anti-deuterons during the space station stage of the experiment. However, the antihelium3/proton abundance does not exceed $4 10^{-13}$. Heavier anti-nuclei are even further suppressed.

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