64 research outputs found
Is the diffuse gamma background radiation generated by galactic cosmic rays?
We explore the possibility that the diffuse gamma-ray background radiation
(GBR) at high galactic latitudes could be dominated by inverse Compton
scattering of cosmic ray (CR) electrons on the cosmic microwave background
radiation and on starlight from our own galaxy. Assuming that the mechanisms
accelerating galactic CR hadrons and electrons are the same, we derive simple
and successful relations between the spectral indices of the GBR above a few
MeV, and of the CR electrons and CR nuclei above a few GeV. We reproduce the
observed intensity and angular dependence of the GBR, in directions away from
the galactic disk and centre, without recourse to hypothetical extragalactic
sources.Comment: Submitted for publicatio
Is there a 1998bw-like supernova in the afterglow of gamma ray burst 011121?
We use the very simple and successful Cannonball Model (CB) of gamma ray
bursts (GRBs) and their afterglows (AGs) to analyze the observations of the
strongly extinct optical AG of the relatively nearby GRB 011121, which were
made with ground-based telescopes at early times, and with the HST at later
time. We show that GRB 011121 was indeed associated with a 1998bw-like
supernova at the GRB's redshift, as we had specifically predicted for this GRB
before the supernova could be observed.Comment: Submitted for publicatio
A common origin of all the species of high-energy cosmic rays?
Cosmic ray nuclei, cosmic ray electrons with energy above a few GeV, and the
diffuse gamma-ray background radiation (GBR) above a few MeV, presumed to be
extragalactic, could all have their origin or residence in our galaxy and its
halo. The mechanism accelerating hadrons and electrons is the same, the
electron spectrum is modulated by inverse Compton scattering on starlight and
on the microwave background radiation; the -rays are the resulting
recoiling photons. The spectral indices of the cosmic-ray electrons and of the
GBR, calculated on this simple basis, agree with observations. The angular
dependence and the approximate magnitude of the GBR are also explained.Comment: Includes a discussion of the contribution of inverse Compton
scattering of CR electrons by starlight in the halo to the gamma background
radiation. One corrected typo. Additional references, and figures to compare
predictions for the angular dependence of the gamma background radiation with
data. Conclusions are unchange
The vicissitudes of "cannonballs": a response to criticisms by A.M. Hillas and a brief review of our claims
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
A solution of a hoary conundrum: the origin and properties of cosmic rays
I discuss a theory of non-solar cosmic rays (CRs) based on a single type of
CR source at all energies. All observed properties of CRs are predicted in
terms of very simple and completely `standard' physics. The source of CRs is
extremely `economical': it has only one parameter to be fitted to the enormous
ensemble of all of the data. All other inputs are `priors', that is theoretical
or observational items of information independent of the properties of the
source of CRs and chosen to lie in their pre-established ranges.Comment: 10 pages, 13 figures. Contribution to the Cosmic Ray International
Seminar, Catania, 200
Origin of the ultrahigh-energy cosmic rays and their spectral break
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, appear to be in conflict if their origin is assumed to be extragalactic. Their spectrum and composition, however, are those expected from Galactic UHECRs accelerated by highly relativistic jets such as those producing short hard gamma ray bursts (SHBs). If this alternative interpretation is
correct, then the observed break in the energy spectrum of UHECRs around 50 EeV is the energy threshold for free escape of UHE iron nuclei from the Galaxy and not the Greisen-Zatsepin-Kuzmin (GZK) cutoff for protons, and the arrival directions of UHECR nuclei with energy above their UHE breaks must point back to their Galactic sources rather than to active galactic nuclei (AGN) within the GZK horizon
Long gamma-ray bursts without visible supernovae: a case study of redshift estimators and alleged novel objects
There is an ongoing debate on whether or not the observational limits on a supernova (SN) associated with GRB060614 convincingly exclude a SN akin to SN1998bw as its originator, and provide evidence for a new class of long-duration GRBs. We discuss this issue in the contexts of indirect `redshift estimators' and of the fireball and cannonball models of GRBs. The latter explains the unusual properties of GRB060614: at its debated low redshift (0.125) they are predicted, as opposed to exceptional, if the associated SN is of `Pastorello's class'. Long-baseline radio data and deep optical data may test the proposed alternatives
The rapid decline of the prompt emission in Gamma-Ray Bursts
Many gamma ray bursts (GRBs) have been observed with the Burst-Alert and
X-Ray telescopes of the Swift satellite. The successive `pulses' of these GRBs
end with a fast decline and a fast spectral softening, until they are overtaken
by another pulse, or the last pulse's decline is overtaken by a less
rapidly-varying `afterglow'. The fast decline-phase has been attributed, in the
currently-explored standard fireball model of GRBs, to `high-latitude'
synchrotron emission from a collision of two conical shells. This high latitude
emission does not explain the observed spectral softening. In contrast, the
temporal behaviour and the spectral evolution during the fast-decline phase
agree with the predictions of the cannonball model of GRBs.Comment: Four added figures comparing the evolution of the inferred effective
photon spectral index during the fast decline phase of the prompt emission in
14 selected Swift GRBS and the cannonball (CB) model predictio
Critical Tests of Leading Gamma Ray Burst Theories II
It has been observationally established that supernovae (SNe) of Type Ic
produce long duration gamma ray bursts (GRBs) and that neutron star mergers
generate short hard GRBs. SN-Less GRBs presumably originate in a phase
transition of a neutron star in a high mass X-ray binary. How these phenomena
actually generate GRBs is debated. The fireball and cannonball models of GRBs
and their afterglows have been widely confronted with the huge observational
data, with their defenders claiming success. The claims, however, may reflect
multiple choices and the use of many adjustable parameters, rather than the
validity of the models. Only a confrontation of key falsifiable predictions of
the models with solid observational data can test their validity. Such critical
tests are reviewed in this report.Comment: An updated rendering of arXiv:1810.03514 with an extra autho
Will relativistic heavy-ion colliders destroy our planet?
Experiments at the Brookhaven National Laboratory will study collisions
between gold nuclei at unprecedented energies. The concern has been voiced that
``strangelets''-hypothetical products of these collisions - may trigger the
destruction of our planet. We show how naturally occurring heavy-ion collisions
can be used to derive a safe and stringent upper bound on the risk incurred in
running these experiments.Comment: LaTeX, no figure
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