Wednesday March 7, 2012 - 4,00 pm

ICRA Seminar - Aula Majorana (Physics Dept., Old Building - Ground Floor)

Title: A complete sample of bright long GRBs discovered by Swift

Abstract: The Swift mission has represented a breakthrough for the detection of GRBs from the local Universe up to the highest redshifts. However, statistical studies of their rest-frame properties and their evolution with cosmic time are still hampered by the fact that most of the observed GRBs lack of redshift measurements. Here we present a carefully selected sub-sample of Swift long GRBs that is complete in redshift. The sample is constructed by considering: i) burst with favorable observing conditions for ground-based follow-up optical/NIR observations and ii) GRBs are bright in the 15-150 keV Swift/BAT band. The sample is composed by 58 burst with a redshift completeness level of 90% (95% is reached by considering also available redshift constraints). In the light of this complete sample, I will discuss the properties of long GRBs and their evolution with cosmic times, focusing in particular on the GRB luminosity function, the prompt emission spectral-energy correlations and the nature of dark bursts.

Wednesday March 21, 2012 - 4,30 pm

ICRA Seminar - Aula Conversi (Physics Dept., Old Building - 1st Floor)

Title: Presupernova evolution and explosion of massive stars

Abstract: I review our recent progresses on the presupernova evolution of massive stars in the range (13-120) Msun of solar metallicity. Special attention will be devoted to the effect rotation and of the mass loss rate in determining the structure and the physical properties of the star prior to the supernova explosion. I will also discuss the explosive yields and the initial mass-remnant mass relation in the framework of the induced explosion and hence the contribution of these stars to the global chemical enrichment of the interstellar medium.

Wednesday March 21, 2012 - 5,30 pm

ICRA Seminar - Aula Conversi (Physics Dept., Old Building - 1st Floor)

Title: Radiative transfer near the photosphere of ultrarelativistic outflows and GRBs

Abstract: We present preliminary results of numerical analysis of radiative transfer in baryonic ultrarelativistic outflows in GRBs. We confirm the recent results obtained by Beloborodov (2011) who finds that photon distribution is strongly anisotropic even in the comoving frame near the photosphere. We extend these results and analyze the energy spectrum of photospheric emission as seen by a distant observer.