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A. De Rujula

Publications and source records attributed to A. De Rujula.

At least 37 records · Page 2Linked to original sources
arXiv2007

On the origin of the correlations between Gamma-Ray Burst observables

Several pairs of observable properties of Gamma Ray Bursts (GRBs) are known to be correlated. Many such correlations are straightforward predictions of the 'cannonball' model of GRBs. We extend our previous discussions of the subject to a wealth of new data, and to correlations between 'lag-time', 'variability' and 'minimum rise-time', with other observables. Schaefer's recent systematic analysis of the observations of many GRBs of known red-shift gives us a good and updated data-basis for our study.

astro-ph↗
arXiv2007

Implications of the Large Polarization Measured in Gamma Ray Bursts

The polarization of the prompt $γ$-ray emission has been measured in four bright gamma ray bursts (GRBs). It was nearly maximal in all cases, as predicted by the Cannonball (CB) model of GRBs long before the observations. These results are inconsistent with standard models of GRBs wherein the prompt emission is due to synchrotron radiation. A much smaller linear polarization is predicted by the CB model for the prompt emission in X-ray flashes (XRFs) and in extremely luminous GRBs. These measurements would provide yet another stringent test of the CB model and its unification of GRBs and XRFs.

astro-ph↗
arXiv2006

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.

hep-ph↗
arXiv2005

The Magnetic Field in Galaxies, Galaxy Clusters, and the InterGalactic Space

Magnetic fields of debated origin appear to permeate the Universe on all large scales. There is mounting evidence that supernovae produce not only roughly spherical ejecta and winds, but also highly relativistic jets of ordinary matter. These jets, which travel long distances, slow down by accelerating the matter encountered on their path to cosmic-ray energies. We show that, if the turbulent motions induced by the winds and the cosmic rays generate magnetic fields in rough energy equipartition, the predicted magnetic-field strengths coincide with the ones observed not only in galaxies (5 $μ$G in the Milky Way) but also in galaxy clusters (6 $μ$G in Coma). The prediction for the intergalactic (or inter-cluster) field is 50 nG.

astro-ph↗
arXiv2004

A Cannonball Model of Cosmic Rays

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.

hep-ph↗
arXiv2004

A Unified Model of High-Energy Astrophysical phenomena

I outline a unified model of high-energy astrophysics, in which the gamma background radiation, cluster "cooling flows", gamma-ray bursts, X-ray flashes and cosmic-ray electrons and nuclei of all energies -share a common origin. The mechanism underlying these phenomena is the emission of relativistic "cannonballs" by ordinary supernovae, analogous to the observed ejection of plasmoids by quasars and microquasars. I concentrate on Cosmic Rays: the longest-lasting conundrum in astrophysics. The distribution of Cosmic Rays 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. The model is only lacking a satisfactory theoretical understanding of the "cannon" that emits the cannonballs in catastrophic episodes of accretion onto a compact object.

astro-ph↗
arXiv2004

The Discovery of a Hyperluminal Source in the Radio Afterglow of GRB 030329

Taylor, Frail, Berger and Kulkarni have made precise VLBI measurements of the size and position of the source of the radio afterglow of GRB 030329. They report a size evolution compatible with standard fireball models, proper motion limits inconsistent with the cannonball model, and a double source, i.e. "an additional compact component" on day 51 after the GRB, totally unexpected in the standard models. We outline a consistent interpretation of the ensemble of the data in the realm of the cannonball model. The observed double source is a radio image of the two cannonballs required in this model to explain the gamma-ray and optical light curves of this GRB; their separation agrees with the expectation. Thus interpreted, the observation of the two sources --separated by a "hyperluminal" distance-- is a major discovery in astrophysics: it pins down the origin of GRBs.

astro-ph↗
arXiv2004

On the Polarization of Gamma Ray Bursts and their Optical Afterglows

The polarization of the optical afterglow (AG) of Gamma-Ray Bursts (GRBs) has only been measured in a few instances at various times after the GRB. In all cases except the best measured one (GRB 030329) the observed polarization and its evolution are simple and easy to explain in the most naive version of the "Cannonball'' model of GRBs: the "intrinsic" AG polarization is small and the observations reflect the "foreground" effects of the host galaxy and ours. The polarization observed in GRB 030329 behaves chaotically, its understanding requires reasonable but ad-hoc ingredients. The polarization of the gamma rays of a GRB has only been measured in the case of GRB 021206. The result is debated, but similar measurements would be crucial to the determination of the GRB-generating mechanism.

astro-ph↗
arXiv2004

The superluminal motion of Gamma-Ray-Burst sources and the complex afterglow of GRB 030329

The source of the very bright Gamma-Ray Burst GRB 030329 is close enough to us for there to be a hope to measure or significantly constrain its putative superluminal motion. Such a phenomenon is expected in the ``Cannonball'' (CB) model of GRBs. Recent precise data on the optical and radio afterglow of this GRB --which demonstrated its very complex structure-- allow us to pin down the CB-model's prediction for the afterglow-source position as a function of time. It has been stated that (the unpublished part of) the new radio data ``unequivocably disprove'' the CB model. We show how greatly exaggerated that obituary announcement was, and how precise a refined analysis of the data would have to be, to be still of interest.

astro-ph↗
arXiv2003

The New Paradigm for Gamma Ray Bursts: a Case of Unethical Behaviour?

One might have hoped that the immediacy and completeness of scientific information provided through the internet would have made the wrongful appropriation of someone else's ideas --now so easy to detect and document-- a sin of the past. Not so. Here I present evidence, which the reader should judge, of such an apparent misconduct by Sir Martin Rees, the British Astronomer Royal, and others. Unethical behaviour is not unknown in science. My sole intention is to call attention to the problem by way of example, in an attempt to contribute to a more ethical atmosphere, which would in my opinion be beneficial to the field.

physics.soc-ph↗
arXiv2003

Towards a complete theory of Gamma Ray Bursts

Gamma Ray Bursts (GRBs) are notorious for their diversity. Yet, they have a series of common features. The typical energy of their $γ$ rays is a fraction of an MeV. The energy distributions are well described by a ``Band spectrum'', with ``peak energies'' spanning a surprisingly narrow range. The time structure of a GRB consists of pulses, superimposed or not, rising and decreasing fast. The number of photons in a pulse, the pulses' widths and their total energy vary within broad but given ranges. Within a pulse, the energy spectrum softens with increasing time. The duration of a pulse decreases at higher energies and its peak intensity shifts to earlier time. Many other correlations between pairs of GRB observables have been identified. Last (and based on one measured event!) the $γ$-ray polarization is very large. A satisfactory theory of GRBs should naturally and very simply explain, among others, all these facts. We show that the "cannonball" (CB) model does it. In the CB model the process leading to the ejection of highly relativistic jetted CBs in core-collapse supernova (SN) explosions is akin to the one observed in quasars and microquasars. The prompt $γ$-ray emission --the GRB-- is explained extremely well by inverse Compton scattering of light in the near environment of the SN by the electrons in the CBs' plasma. We have previously shown that the CB-model's description of GRB afterglows as synchrotron radiation from ambient electrons --swept in and accelerated within the CBs-- is also simple, universal and very successful. The only obstacle still separating the CB model from a complete theory of GRBs is the theoretical understanding of the CBs' ejection mechanism in SN explosions.

astro-ph↗
arXiv2003

Gamma-ray bursts and the sociology of science

I discuss what we have learned about Gamma-Ray Bursts (GRBs) by studying their `afterglows', and how these are interpreted in the generally-accepted `fireball' model of GRBs, as well as in the generally-unaccepted `cannonball' model of the same phenomena. The interpretation of GRBs is a good example around which to frame a discussion of the different approaches to science found in various fields, such as high-energy physics (HEP), high-energy astrophysics, or even the deciphering of ancient languages. I use this example to draw conclusions on `post-academic' science, and on the current status of European HEP.

hep-ph↗
arXiv2002

On the radio afterglow of gamma ray bursts

We use the cannonball (CB) model of gamma ray bursts (GRBs) to predict the spectral and temporal behaviour of their radio afterglows (AGs). A single simple expression describes the AGs at all times and frequencies; its high-frequency limit reproduces the successful CB model predictions for optical and X-ray AGs. We analyze all of the observed radio AGs of GRBs with known redshifts, including those of the exceptionally close-by GRB 980425. We also study in detail the time-evolution of the AGs' spectral index. The agreement between theory and observations is excellent, even though the CB model is extremely frugal in the number of parameters required to explain the radio observations. We propose to use the scintillations in the radio AGs of GRBs to verify and measure the hyperluminal speed of their jetted CBs, whose apparent angular velocity is of the same order of magnitude as that of galactic pulsars, consistently measured directly, or via scintillations.

astro-ph↗
arXiv2002

GRBs in the Cannonball model: an overview

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.

astro-ph↗
arXiv2002

On the optical and X-ray afterglows of gamma ray bursts

We severely criticize the consuetudinary analysis of the afterglows of gamma-ray bursts (GRBs) in the conical-ejection fireball scenarios. We argue that, instead, recent observations imply that the long-duration GRBs and their afterglows are produced by highly relativistic jets of cannonballs (CBs) emitted in supernova explosions. The CBs are heated by their collision with the supernova shell. The GRB is the boosted surface radiation the CBs emit as they reach the transparent outskirts of the shell. The exiting CBs further decelerate by sweeping up interstellar matter (ISM). The early X-ray afterglow is dominated by thermal bremsstrahlung from the cooling CBs, the optical afterglow by synchrotron radiation from the ISM electrons swept up by the CBs. We show that this model fits simply and remarkably well all the measured optical afterglows of the 15 GRBs with known redshift, including that of GRB 990123, for which unusually prompt data are available. We demonstrate that GRB 980425 was a normal GRB produced by SN1998bw, with standard X-ray and optical afterglows. We find that the very peculiar afterglow of GRB 970508 can be explained if its CBs encountered a significant jump in density as they moved through the ISM. The afterglows of the nearest 8 of the known-redshift GRBs show various degrees of evidence for an association with a supernova akin to SN1998bw. In all other cases such an association, even if present, would have been undetectable with the best current photometric sensitivities. This gives strong support to the proposition that most, maybe all, of the long-duration GRBs are associated with supernovae. Though our emphasis is on optical afterglows, we also provide an excellent description of X-ray afterglows.

astro-ph↗
arXiv2002

The threat to life from Eta Carinae and gamma ray bursts

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.

astro-ph↗