3,006,749 research outputs found
Correlated Spectral And Temporal Behaviour Of Late-Time Afterglows Of Gamma Ray Bursts
The cannonball (CB) model of gamma ray bursts (GRBs) predicts that the
asymptotic behaviour of the spectral energy density of the X-ray afterglow of
GRBs is a power-law in time and in frequency where the difference between the
temporal and spectral power-law indexes, , is restricted to
the values 0, 1/2 and 1. Here we report the distributions of the values
, and their difference for a sample of 315 Swift GRBs. This
sample includes all Swift GRBs that were detected before August 1, 2012, whose
X-ray afterglow extended well beyond 1 day and the estimated error in
was . The values of were extracted
from the CB model fits to the entire light curves of their X-ray afterglow
while the spectral index was extracted by the Swift team from the time
integrated X-ray afterglow of these GRBs. We found that the distribution of the
difference for these 315 Swift GRBs has three narrow peaks
around 0, 1/2 and 1 whose widths are consistent with being due to the
measurement errors, in agreement with the CB model prediction.Comment: 12 figures, added references, used data reported in the Swift/XRT
light-curve repositor
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 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
Dark Matter and Big Bang Nucleosynthesis
The recently observed Deuterium abundance in a low- metallicity high-redshift
hydrogen cloud, which is about ten times larger than that observed in the near
interstellar medium, is that expected from the Standard Big Bang
Nucleosynthesis theory and the observed abundances of He and Li
extrapolated to their primordial values. The inferred cosmic baryon to photon
ratio, yields a mean cosmic baryon
density, in critical mass units, of with being the Hubble constant in units of . This baryon density is consistent with the mean cosmic density of
matter visible optically and in X-rays. It implies that most of the baryons in
the Universe are visible and are not dark. Combined with the observed ratio of
baryons to light in X-ray emitting clusters, it yields the value for the mean mass density of the Universe, which is consistent
with that obtained from the mass to light ratio in clusters. This mass density
is about ten times larger than the mean baryon mass density. It indicates that
most of the matter in the Universe consists of nonbaryonic dark matter.Comment: Invited talk to be published in the proceedings of ``Dark Matter In
Cosmology'' (Villars sur Ollon, Switzerland January 21-28, 1995
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