arXiv subjects

Antonio de Ugarte-Postigo

Publications and source records attributed to Antonio de Ugarte-Postigo.

3 recordsLinked to original sources

arXiv2015

Numerical Models of Blackbody-Dominated GRBs

Blackbody-dominated (BBD) gamma-ray bursts (GRBs) are events characterized by the absence of a typical afterglow, long durations and the presence of a significant thermal component following the prompt gamma-ray emission. GRB 101225A (the `Christmas burst') is a prototype of this class. A plausible progenitor system for it, and for the BBD-GRBs, is the merger of a neutron star (NS) and a helium core of an evolved, massive star. Using relativistic hydrodynamic simulations we model the propagation of an ultrarelativistic jet through the enviroment created by such a merger and we compute the whole radiative signature, both thermal and non-thermal, of the jet dynamical evolution. We find that the thermal emission originates from the interaction between the jet and the hydrogen envelope ejected during the NS/He merger.

astro-ph.HE↗

arXiv2014

Numerical models of blackbody-dominated gamma-ray bursts -- II. Emission properties

Blackbody-dominated (BBD) gamma-ray bursts (GRBs) are events characterized by long durations and the presence of a significant thermal component following the prompt emission, as well as by the absence of a typical afterglow. GRB 101225A is the most prominent member of this class. A plausible progenitor system for it and for BBD-GRBs is the merger a neutron star and a helium core of an evolved, massive star. Using relativistic hydrodynamic simulations we model the propagation of ultrarelativistic jets through the environments created by such mergers. In a previous paper we showed that the thermal emission in BBD-GRBs is linked to the interaction of an ultrarelativistic jet with the ejected envelope of the secondary star of the binary. Here we focus on explaining the emission properties of BBD-GRBs computing the whole radiative signature (both thermal and non-thermal) of the jet dynamical evolution. The non-thermal emission of the forward shock of the jet is dominant during the early phases of the evolution, when that shock is moderately relativistic. Our models do not produce a classical afterglow because the quick deceleration of the jet results primarily from the mass entrainment in the beam, and not from the process of plowing mass from the external medium in front of the GRB ejecta. The contribution of the reverse shock is of the same magnitude than that of the forward shock during the first 80 min after the GRB. Later, it quickly fades because the jet/environment interaction chocks the ultrarelativistic jet beam and effectively dumps the reverse shock. In agreement with observations, we obtain rather flat light curves during the first 2 d after the GRB, and a spectral evolution consistent with the observed reddening of the system.

astro-ph.HE↗

arXiv2009

MAGIC observation of GRB080430

Gamma-ray bursts are cosmological sources emitting radiation from the gamma-rays to the radio band. Substantial observational efforts have been devoted to the study of GRBs during the prompt phase, i.e. the initial burst of high-energy radiation, and during the longer-lasting afterglows. In spite of many successes in interpreting these phenomena there are still several open key questions about the fundamental emission processes, their energetics and the environment. Moreover, independently of their modeling, GRB spectra are remarkably simple, being satisfactorily fitted with power-laws, and therefore offer a very valuable tool to probe the extragalactic background light distribution affecting all high-energy observations of cosmological sources. Observations carried out with Cherenkov telescopes, as MAGIC, can be fundamental for all these scientific topics. GRB080430, being at a rather moderate redshift, z~0.76, and well-studied in the optical, although observed only a few hours after the high-energy event, is a good test case to evaluate the perspective for late-afterglow observations with ground based GeV/TeV observatories.

astro-ph.HE↗