613 research outputs found

    What SWIFT has taught us about X-ray flashes and long-duration gamma-ray bursts

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    Recent data gathered and triggered by the SWIFT satellite have greatly improved our knowledge of long-duration gamma ray bursts (GRBs) and X-ray flashes (XRFs). This is particularly the case for the X-ray data at all times, and for UV and optical data at very early times. I show that the optical and X-ray observations are in excellent agreement with the predictions of the "cannonball" model of GRBs and XRFs. Elementary physics and just two mechanisms underlie these predictions: inverse Compton scattering and synchrotron radiation, generally dominant at early and late times, respectively. I put this result in its proper context and dedicate the paper to those who planed, built and operate SWIFT, a true flying jewel.Comment: A talk at the 2007 Frascati Workshop, Vulcano, Italy. 12 pages total, 17 figure

    GRBs in the Cannonball model: an overview

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    The cannonball model of GRBs is very overt (and, thus, falsifiable) in its hypothesis and results: all the considerations I review are based on explicit analytical expressions derived, in fair approximations, from first principles. The model provides a good description of all the data on all GRBs of known redshift, has made correct predictions, and is unprecedentedly self-consintent, simple and successful.Comment: 8 pages, 7 figures in text. To appear in the Proceedings of the 4th Microquasar Workshop, 2002, eds. Durouchoux, Fuchs & Rodriguez, published by the Center for Space Physics: Kolkata. Slightly longer versio

    A Cannonball Model of Cosmic Rays

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    I outline a "Cannon-Ball" model of Cosmic Rays in which their distribution in the Galaxy, their total "luminosity", the broken power-law spectra with their observed slopes, the position of the knee(s) and ankle(s), and the alleged variations of composition with energy are all explained in terms of simple and "standard" physics.Comment: 10 pages, 7 figures. To appear in the proceedings of the XIII International Symposium on Very High Energy Cosmic Ray Interactions, Pylos, Greece, 200

    Optical and X-ray Afterglows in the Cannonball Model of GRBs

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    The Cannonball Model is based on the hypothesis that GRBs and their afterglows are made in supernova explosions by relativistic ejecta similar to the ones observed in quasars and microquasars. Its predictions are simple, and analytical in fair approximations. The model describes well the properties of the Îł\gamma-rays of GRBs. It gives a very simple and extremely successful description of the optical and X-ray afterglows of {\it all} GRBs of known redshift. The only problem the model has, so far, is that it is contrary to staunch orthodox beliefs.Comment: 11 pages, 16 figures. Talk at the GRB 2001 Conference in Woods Hole, Mas

    The threat to life from Eta Carinae and gamma ray bursts

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    Eta Carinae, the most massive and luminous star known in our galaxy, is rapidly boiling matter off its surface. At any time its core could collapse into a black hole, which may result in a gamma-ray burst (GRB) that can devastate life on Earth. Auspiciously, recent observations indicate that the GRBs are narrowly beamed in cones along the rotational axis of the progenitor star. In the case of Eta Carinae the GRBs will not point to us, but will be ravaging to life on planets in our galaxy that happen to lie within the two beaming cones. The mean rate of massive life extinctions by jets from GRBs, per life-supporting planet in galaxies like ours, is once in 100 million years, comparable to the rate of major extinctions observed in the geological records of our planet.Comment: Published in Astrophysics and Gamma Ray Physics in Space (eds. A. Morselli and P. Picozza), Frascati Physics Series Vol. XXIV (2002), pp. 513-52

    The Cannonball Model of Gamma Ray Bursts: Lines in the X-Ray Afterglow

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    Recent observations suggest that gamma-ray bursts (GRBs) and their afterglows are produced by jets of highly relativistic cannonballs (CBs), emitted in supernova explosions. The fully ionized CBs cool to a temperature below 4500 K within a day or two, at which point electron-proton recombination produces an intense Lyman-α\alpha emission. The line energy is Doppler-shifted by the CBs' motion to X-ray energies in the observer's frame. The measured line energies, corrected for their cosmological redshift, imply Doppler factors in the range 600 to 1000, consistent with those estimated -in the CB model- from the characteristics of the γ\gamma-ray bursts. All other observed properties of the lines are also well described by the CB model. Scattering and self-absorption of the recombination lines within the CB also produce a wide-band flare-up in the GRB afterglow, as the observations indicate. A very specific prediction of the CB model is that the X-ray lines ought to be narrow and move towards lower line energies as they are observed: their current apparently large widths would be the effect of time integration, and/or of the blending of lines from CBs with different Doppler factors.Comment: 8 pages, no figure

    The vicissitudes of "cannonballs": a response to criticisms by A.M. Hillas and a brief review of our claims

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    A.M. Hillas, in a review of the origins of cosmic rays, has recently criticized the "cannonball" (CB) model of cosmic rays and gamma-ray bursts. We respond to this critique and take the occasion to discuss the crucial question of particle acceleration in the CB model and in the generally accepted models. We also summarize our claims concerning the CB model.Comment: 3.3 pages, no figure

    Scars on the CBR?

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    We ask whether the universe can be a patchwork consisting of distinct regions of matter and antimatter. In previous work we demonstrated that post-recombination matter-antimatter contact near regional boundaries leads to an observable (but unobserved) gamma-ray flux for domain sizes of less than a few thousand Mpc, thereby excluding such domains. In this paper we consider the pre-recombination signal from domains of larger size.Comment: 6 pages, late

    Origin of the Ultrahigh-Energy Cosmic Rays and their Spectral Break

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    The energy spectrum, composition and arrival directions of ultrahigh energy cosmic rays (UHECRs) with energy above the cosmic ray ankle, measured by the Pierre Auger Observatory, are inconsistent if their origin is assumed to be extragalactic. Their observed properties, however, are those expected from UHECRs accelerated by the highly relativistic jets emitted in Galactic gamma ray bursts, most of which are beamed away from Earth. If this alternative interpretation is correct, the observed break in the energy spectrum of UHECRs around 50 EeV is not the Greisen-Zatsepin-Kuzmin cutoff but the energy threshold for free escape of ultrahigh energy iron cosmic rays from the Galaxy and above their respective free-escape threshold-energies, UHECR nuclei should point back to their Galactic sources or their remnants rather than to active galactic nuclei (AGN) within the GZK horizon.Comment: Invited talk presentet by A. Dar at the Rencontre de La Thuile, 2011. To be published in Nuovo Ciment
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