相关论文: Time dependent photoionization opacities in dense …
If gamma-ray bursts are associated with dense star-forming regions in young galaxies, photoelectric absorption by the dense circumburster material (CBM) will occur. As the burst evolves, the surrounding material is photoionized, leading to…
Despite great observational and theoretical effort, the burst progenitor is still a mysterious object. It is generally accepted that one of the best ways to unveil its nature is the study of the properties of the close environment in which…
We investigate through dedicated numerical simulations the evolution of the soft X-ray absorption properties of a cloud surrounding a gamma-ray burst source. We show that the absorption properties of the material are strongly modified by…
We report the discovery of a transient equivalent hydrogen column density with an absorption edge at ~3.8 kiloelectron volts in the spectrum of the prompt x-ray emission of gamma-ray burst (GRB) 990705. This feature can be satisfactorily…
The discovery of Gamma-Ray Burst (GRB) afterglows revealed a new class of variable sources at optical and radio wavelengths. At present, the environment and precise redshift of the detected afterglows are still unknown. We show that if a…
The properties of the ambient medium in which GRBs go off are an important piece of the puzzle, not only as an issue in itself, but because of their link with the nature of the progenitor. In this review, I describe and critically comment…
The absorption feature detected in the prompt X-ray emission of GRB 990705 bears important consequences. We investigate different production mechanisms and we conclude that the absorbing material cannot be very close to the burster and is…
Absorption and Reprocessing of Gamma-ray burst radiation in the environment of cosmological GRBs can be used as a powerful probe of the elusive nature of their progenitors. In particular, transient X-ray emission line and absorption…
We study the > 10 ratios in the X-ray to optical column densities inferred from afterglow spectra of Gamma Ray Bursts due to gas surrounding their progenitors. We present time-evolving photoionization calculations for these afterglows and…
The recent detection of a transient absorption feature in the prompt emission of GRB 990705 has sparked multiple attempts to fit this feature in terms of photoelectric absorption or resonance scattering out of the line of sight to the…
The 1-100 pc region embedding long-duration gamma-ray bursts (lGRBs) has been hitherto unexplored, as extremely high ionisation by the GRB prevents application of optical absorption spectroscopy on such distances. We show that the GRB…
The interaction of a radiation field with a dusty medium is a relevant issue in several astrophysical contexts. We use the time-dependent photoionization code in a dusty medium developed by Perna & Lazzati (2002), to study the modifications…
We present a time-dependent photoionization code that combines self-consistently metal evolution and dust destruction under an intense X-ray UV radiation field. Firstly, we extend the mathematical formulation of the time-dependent evolution…
In recent years, our understanding of gamma-ray bursts (GRB) prompt emission has been revolutionized, due to a combination of new instruments, new analysis methods and novel ideas. In this review, I describe the most recent observational…
We calculate the prompt x-ray emission as a function of viewing angle for beamed Gamma-Ray Burst (GRB) sources. Prompt x-rays are inevitable due to the less highly blueshifted photons emitted at angles greater than 1/gamma relative to the…
The energy output in the gamma-ray burst (GRB) prompt emission and afterglow phase is expected to photoionize the surrounding medium out to large radii. Cooling of this gas produces line emission, particularly strong in the optical, whose…
Highly radiative expansion of a relativistic shell is shown to explain all observed features of the afterglows of the two bursts GRB 970228 and GRB 970508. In particular, in the first case the observed time-dependence t^-1.32 of the soft…
We discuss the effect of dispersion delay due to intervening ionized media in the radio emission of gamma-ray bursts (GRBs). For high redshift GRBs ($z \ga 3$), the ionized intergalactic medium (IGM) should be the dominant source of…
The degree and the temporal evolution of linear polarization in the prompt and afterglow emission of gamma-ray bursts is a very robust diagnostic of some key features of gamma-ray bursts jets and their micro and macro physics. In this…
The observational diversity of optical emission, which coincides with prompt gamma-ray bursts (GRBs), has been discovered in the recent Swift era. We show that on the assumption of the synchrotron radiation for the observed energy range…