The canonical Gamma‐Ray Bursts and their “precursors”

AIP Conference Proceedings 10/2008; 1065(1):219-222. DOI: 10.1063/1.3027915
Source: arXiv

ABSTRACT The fireshell model for Gamma‐Ray Bursts (GRBs) naturally leads to a canonical GRB composed of a proper‐GRB (P‐GRB) and an afterglow. P‐GRBs, introduced by us in 2001, are sometimes considered “precursors” of the main GRB event in the current literature. We show in this paper how the fireshell model leads to the understanding of the structure of GRBs, with precise estimates of the time sequence and intensities of the P‐GRB and the of the afterglow. It leads as well to a natural classification of the canonical GRBs which overcomes the traditional one in short and long GRBs.

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    ABSTRACT: (Shortened) [...] After recalling the basic features of the "fireshell model", we emphasize the following novel results: 1) the interpretation of the X-ray flares in GRB afterglows as due to the interaction of the optically thin fireshell with isolated clouds in the CircumBurst Medium (CBM); 2) an interpretation as "fake - disguised" short GRBs of the GRBs belonging to the class identified by Norris & Bonnell [...] consistent with an origin from the final coalescence of a binary system in the halo of their host galaxies with particularly low CBM density [...]; 3) the first attempt to study a genuine short GRB with the analysis of GRB 050509B, that reveals indeed still an open question; 4) the interpretation of the GRB-SN association in the case of GRB 060218 via the "induced gravitational collapse" process; 5) a first attempt to understand the nature of the "Amati relation", a phenomenological correlation between the isotropic-equivalent radiated energy of the prompt emission E_{iso} with the cosmological rest-frame \nu F_{\nu} spectrum peak energy E_{p,i}. In addition, recent progress on the thermalization of the electron-positron plasma close to their formation phase, as well as the structure of the electrodynamics of Kerr-Newman Black Holes are presented. An outlook for possible explanation of high-energy phenomena in GRBs to be expected from the AGILE and the Fermi satellites are discussed. As an example of high energy process, the work by Enrico Fermi dealing with ultrarelativistic collisions is examined. It is clear that all the GRB physics points to the existence of overcritical electrodynamical fields. In this sense we present some progresses on a unified approach to heavy nuclei and neutron stars cores, which leads to the existence of overcritical fields under the neutron star crust. Comment: 68 pages, 50 figures, in the Proceedings of the XIII Brazilian School on Cosmology and Gravitation, M. Novello, S.E. Perez-Bergliaffa, editors
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    ABSTRACT: (Shortened) GRB080319B, with an isotropic energy E_{iso}=1.32x10^{54}erg, and GRB050904, with E_{iso}=1.04x10^{54}erg, offer the possibility of studying the spectral properties of the prompt radiation of two of the most energetic Gamma-Ray Bursts (GRBs). This allows us to probe the validity of the fireshell model for GRBs beyond 10^{54}erg, well outside the energy range where it has been successfully tested up to now (10^{49}-10^{53}erg). We find that in the low energy region, the prompt emission spectra observed by Swift BAT reveals more power than theoretically predicted. The opportunities offered by these observations to improve the fireshell model are outlined. One of the distinguishing features of the fireshell model is that it relates the observed spectra to the spectrum in the comoving frame of the fireshell. Originally, a fully radiative condition and a comoving thermal spectrum were adopted. An additional power-law in the comoving thermal spectrum is required [...] in the fireshell model for GRBs 080319B and 050904. A new phenomenological parameter \alpha is correspondingly introduced in the model. We perform numerical simulations of the prompt emission in the Swift BAT bandpass by assuming different values of \alpha [...]. We compare them with the GRB080319B and GRB050904 observed time-resolved spectra, as well as with their time-integrated spectra and light curves. Although GRB080319B and GRB050904 are at very different redshifts (z=0.937 and z=6.29 respectively), a value of \alpha=-1.8 leads for both of them to a good agreement between the numerical simulations and the observed BAT light curves, time-resolved and time-integrated spectra. Such a modified spectrum is also consistent with the observations of previously analyzed less energetic GRBs and reasons for this additional agreement are given. Perspectives for future low energy missions are outlined.
    The Astrophysical Journal 06/2012; 756(1). · 6.28 Impact Factor
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    ABSTRACT: We carried out a systematic search of precursors on the sample of short gamma-ray bursts (GRBs) observed by Swift. We found that ~8%-10% of short GRBs display such early episodes of emission. One burst (GRB 090510) shows two precursor events, the former ~13 s and the latter ~0.5 s before the GRB. We did not find any substantial difference between the precursor and the main GRB emission, and between short GRBs with and without precursors. We discuss possible mechanisms to reproduce the observed precursor emission within the scenario of compact object mergers. The implications of our results on quantum gravity constraints are also discussed.
    The Astrophysical Journal 10/2010; 723(2):1711. · 6.28 Impact Factor

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