arXiv subjects

Alvaro De Rujula

Publications and source records attributed to Alvaro De Rujula.

17 recordsLinked to original sources

arXiv2018

Cannonball model diagnosis of the short gamma ray burst 170817A

The rich and complex data obtained from multi-wavelength observations of SHB170817A, the short hard gamma ray burst (SHB) associated with GW170817 --the first neutron stars merger event detected in gravitational waves (GWs)-- are analyzed in the framework of the cannonball model of SHBs. In this model a highly relativistic jet is launched by fall back matter on the nascent neutron star (or black hole) into a surrounding glory (light from the surrounding wind nebula of the binary neutron stars) which was present already before the merger. The SHB was produced by inverse Compton scattering of glory photons by the jet, which was viewed far off-axis. The fading glory, which produced the initial UVOIR afterglow, was powered by a neutron star remnant. It was overtaken by a late time X-ray, UVOIR and radio afterglow produced by synchrotron radiation from the decelerating jet in the interstellar medium of the host galaxy. If the radio afterglow of SHB170817A was indeed produced by the jet, it should display a superluminal motion relative to the SHB location, still detectable in VLA and VLBI radio observations.

astro-ph.HE↗

arXiv2008

A theory of Cosmic Rays

We present a theory of non-solar cosmic rays (CRs) in which the bulk of their observed flux is due to a single type of CR source at all energies. The total luminosity of the Galaxy, the broken power-law spectra with their observed slopes, the position of the `knee(s)' and `ankle', and the CR composition and its variation with energy are all 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 ensemble of all of the mentioned 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. The theory is part of a `unified view of high-energy astrophysics' --based on the `Cannonball' model of the relativistic ejecta of accreting black holes and neutron stars. The model has been extremely successful in predicting all the novel properties of Gamma Ray Bursts recently observed with help of the Swift satellite. If correct, this model is only lacking a satisfactory theoretical understanding of the `cannon' that emits the cannonballs in catastrophic processes of accretion.

hep-ph↗

arXiv2007

On the X-Ray emission of Gamma Ray Bursts

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. We show that the entire X-ray observations are in excellent agreement with the predictions of the `cannonball' model of GRBs and XRFs, which are based on simple physics and were published long before the launch of SWIFT. Two mechanisms underlie these predictions: inverse Compton scattering and synchrotron radiation, generally dominant at early and late times, respectively. The former mechanism provides a unified description of the gamma-ray peaks, X-ray flares and even the optical `humps' seen in some favourable cases; i.e. their very different durations, fluxes and peak-times are related precisely as predicted. The observed smooth or bumpy fast decay of the X-ray light curve is correctly described case-by-case, in minute detail. The `canonical' X-ray plateau, as well as the subsequent gradual steepening of the afterglow to an asymptotic power-law decay, are as foretold. So are the chromatic and achromatic properties of the light-curves.

astro-ph↗

arXiv2004

Fifty years of Yang-Mills Theories: a phenomenological point of view

On the occasion of the celebration of the first half-century of Yang--Mills theories, I am contributing a personal recollection of how the subject, in its early times, confronted physical reality, that is, its "phenomenology". There is nothing original in this work, except, perhaps, my own points of view. But I hope that the older practitioners of the field will find here grounds for nostalgia, or good reasons to disagree with me. Younger addicts may learn that history does not resemble at all what is reflected in current textbooks: it was orders of magnitude more fascinating.

hep-ph↗

arXiv2004

On the origin of X-ray Flashes

We use the cannonball (CB) model of gamma ray bursts (GRBs) and their afterglows (AGs) to analyze the observational data on X-ray flashes (XRFs) and their AGs. We show that the observations support the CB-model interpretation that XRFs, like GRBs, are produced by the explosions of core-collapse supernovae (SNe) akin to SN1998bw, by jets of highly-relativistic CBs. The XRFs and GRBs are intrinsically identical objects, but the XRFs are viewed from angles (relative to the jet direction) which are typically a few times larger than the typical viewing angles of ``classical'', long-duration GRBs. There should be XRFs, not observed so far, with durations similar to those of short GRBs.

astro-ph↗

arXiv2003

Cooling flows or warming rays?

The radiative cooling time of the X-ray-emitting plasma near the center in many clusters of galaxies is shorter than the age of the cluster, but neither the expected large drop in central temperature --nor the expected mass flow towards the pressure-depleted cluster centers-- are observed. We propose a solution to these ``cooling flow'' problems wherein energy is supplied to the plasma by hadronic cosmic rays (CRs). The solution requires an energy deposition more intense and more distributed than in conventional CR models, but this alternative model is also successful in describing the origin of CRs, as well as the properties of gamma ray bursts and of the diffuse gamma background radiation. The X-ray energy emitted by clusters is supplied, in a quasi-steady state, by the hadronic CRs, which act as ``warming rays''. The temperature distribution in the intracluster space is successfully predicted from the measured plasma-density distribution. Four other puzzling features of clusters can also be explained in simple terms: the discrepancy between their ``virial'' and ``lensing'' masses, their large magnetic fields, the correlation between their optical and X-ray luminosities, and the non-thermal tail of their X-ray spectrum.

astro-ph↗

arXiv2003

The Supernova associated with GRB 030329

The relative proximity of the recent gamma ray burst (GRB) 030329 resulted in a large gamma-ray fluence and in the brightest-ever afterglow (AG), hours after the burst, in the radio, optical and X-ray bands, permitting precise AG measurements, sensitive tests of models and an excellent occasion to investigate the association of GRBs with supernovae (SNe). The Cannonball (CB) model provides a good, simple and universal description of all AGs of GRBs of known redshift, so that it is straightforward to use it to predict what the expected SN signatures are. In the case of GRB 030329, 10 days after burst the AG should begin to reveal the lightcurve, spectrum and polarization of an underlying SN --akin to SN1998bw-- which will peak in the NIR/optical band around day 15. These effects will be easily observable if indeed SN1998bw is a good ``standard candle'' for GRB-associated SNe and if the so far unknown extinction in the host galaxy is not too large.

astro-ph↗

arXiv2003

What we learn from the afterglow of GRB 021211

The behaviour of the afterglow (AG) of gamma-ray bursts (GRBs) directly provides, in the cannonball (CB) model, information about the environment of their progenitor stars. The well observed early temporal decline of the AG of GRB 021211 is precisely the one predicted in the presence of a progenitor's ``wind'' which resulted in a density profile $\propto 1/r^2$ around the star. The subsequent fast fading --which makes this GRB ``quasi-dark''-- is the one anticipated if, further away, the interstellar density is roughly constant and relatively high. The CB-model fit to the AG clearly shows the presence of an associated supernova akin to SN1998bw, and allows even for the determination of the broad-band spectrum of the host galaxy. GRB 990123 and GRB 021004, whose AGs were also measured very early, are also discussed.

astro-ph↗

arXiv2002

Fireballs and cannonballs confront the afterglow of GRB 991208

Galama et al. have recently reported their follow-up measurements of the radio afterglow (AG) of the Gamma Ray Burst (GRB) 991208, up to 293 days after burst, and their reanalysis of the broad-band AG, in the framework of standard fireball models. They advocate a serious revision of their prior analysis and conclusions, based on optical data and on their earlier observations during the first two weeks of the AG. We comment on their work and fill a lacuna: these authors have overlooked the possibility of comparing their new data to the available predictions of the cannonball (CB) model, based --like their incorrect predictions-- on the first round of data. The new data are in good agreement with these CB-model predictions. This is in spite of the fact that, in comparison to the fireball models, the CB model is much simpler, much more predictive, has many fewer parameters, practically no free choices... and it describes well --on a universal basis-- all the measured AGs of GRBs of known redshift.

astro-ph↗

arXiv2002

On the X-ray lines in the afterglows of GRBs

The observation of X-ray lines in the afterglow of GRB 011211 has been reported, and challenged. The lines were interpreted as blue-shifted X-rays characteristic of a set of photoionized ``metals'', located in a section of a supernova shell illuminated by a GRB emitted a couple of days after the supernova explosion. We show that the most prominent reported lines coincide with the ones predicted in the ``cannonball'' model of GRBs. In this model, the putative signatures are Hydrogen lines, boosted by the (highly relativistic) motion of the cannonballs (CBs). The corresponding Doppler boost can be extracted from the fit to the observed I-, R- and V-band light-curves of the optical afterglow of GRB 011211, so that, since the redshift is also known, the line energies are --in the CB model-- predicted. We also discuss other GRBs of known redshift which show spectral features generally interpreted as Fe lines, or Fe recombination edges. The ensemble of results is very encouraging from the CB-model's point of view, but the data on each individual GRB are not good enough to draw (any) objectively decisive conclusions. We outline a strategy for X-ray observers to search for lines which, in the CB model, move predictably from higher to lower energies.

astro-ph↗

arXiv2002

Is the afterglow of Gamma Ray Burst 021004 unusual?

The bumpy light-curve of the bright optical afterglow (AG) of gamma ray burst (GRB) 021004, its spectral evolution and its radio emission have been claimed to be unusual. In the Cannonball Model of GRBs that is not the case. The very early AG's shape is, as for GRB 990123, a direct tracer of the expected circumburst density profile. The unprecedented precision of the data allows for the ``resolution'' of two cannonballs (CBs) in the AG. These two CBs correspond to the two pulses in the GRB and to the two wide humps in the AG light curve. The smaller wiggles in the AG are, as for GRBs 000301c and 970508, to be expected: they trace moderate deviations from a constant density interstellar medium. The observed evolution of the optical spectrum is that predicted in the CB model. The X-ray and radio emissions of GRB 021004 are also normal.

astro-ph↗

arXiv2002

The supernova associated with GRB 020405

We use the very simple and successful Cannonball (CB) model of gamma ray bursts (GRBs) and their afterglows (AGs) to analyze the observations of the mildly extinct optical AG of the relatively nearby GRB 020405. We show that GRB 020405 was associated with a 1998bw-like supernova (SN) at the GRB's redshift that appeared dimmer and redder than SN1998bw because of extinction in the host and our Galaxy. The case for the SN/GRB association --advocated in the CB model-- is becoming indubitable. We discuss the extent to which the GRB/SN connection is model-dependent.

astro-ph↗

arXiv2002

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.

astro-ph↗

arXiv2002

Is there a 1998bw-like supernova in the afterglow of gamma ray burst 010921?

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 GRB 010921 with ground-based telescopes at early times, and with the HST at later time. We show that GRB 010921 was indeed associated with a 1998bw-like supernova at the GRB's redshift.

astro-ph↗

arXiv2001

Supernova search in the afterglow of gamma ray burst 011121

In order to assist in planing the search of supernova (SN) in the late time afterglow (AG) of the gamma ray burst (GRB) 011121 we use the Cannonball Model of GRBs and the observations of its afterglow in the R band in the first two days to predict its late time decline and intrinsic spectrum.

astro-ph↗

arXiv2000

A cannonball model of gamma-ray bursts: superluminal signatures

Recent observations suggest that the long-duration gamma ray bursts (GRBs) and their afterglows are produced by highly relativistic jets emitted in supernova explosions. We propose that the result of the event is not just a compact object plus the ejecta: within a day, a fraction of the parent star falls back to produce a thick accretion disk. The subsequent accretion generates jets and constitutes the GRB ``engine'', as in the observed ejection of relativistic ``cannonballs'' of plasma by microquasars and active galactic nuclei. The GRB is produced as the jetted cannonballs exit the supernova shell reheated by the collision, re-emitting their own radiation and boosting the light of the shell. They decelerate by sweeping up interstellar matter, which is accelerated to cosmic-ray energies and emits synchrotron radiation: the afterglow. We emphasize here a smoking-gun signature of this model of GRBs: the superluminal motion of the afterglow, that can be searched for ---the sooner the better--- in the particular case of GRB 980425.

astro-ph↗

arXiv1997

Avatars of a Matter-Antimatter Universe

An elegantly symmetric Universe, consisting of large islands of matter and antimatter, is by no means obviously out of the question. I review the observations that lead to the usual prejudice that the Universe contains only matter. I discuss recent work inferring that this prejudice can be converted into an inescapable conclusion. I argue that our theoretical conviction should not discourage direct searches for antimatter in cosmic rays.

astro-ph↗