Fireballs in January

Dr. Nasser Maleki (January 25, 1953 – January 6, 2012)

Spectral Implications of Variability in GRB Fireballs∗

Ravi P. Pilla Department of Physics, Columbia University, New York, NY 10027, USA; [email protected] Abraham Loeb Astronomy Department, Harvard University 60 Garden Street, Cambridge, MA 02138, USA; [email protected] Cosmological γ-ray bursts originate from relativistic winds. Temporal fluctuations in the wind velocity can give rise to internal shocks which dissipate a significa...

Fireballs with a Neutron Component

Standard GRB fireballs must carry free neutrons. This crucially changes the mechanism of fireball deceleration by an external medium. As the ion fireball decelerates, the coasting neutrons form a leading front. They gradually decay, leaving behind a relativistic trail of decay products mixed with the ambient medium. The ion fireball sweeps up the trail and drives a shock wave in it. Thus, obser...

Cold Kaons from Hot Fireballs

The E814-collaboration has found a component of very low m t K + mesons with a slope parameter of T 15 MeV. We will present a scenario which explains the observed slope parameter and which allows us to predict the expected slope parameter for kaons produced in heavier systems such as Au+Au. Implications for the restoration of chiral symmetry in relativistic heavy ion collisions are discussed.

Re–born fireballs in Gamma-Ray Bursts

We consider the interaction between a relativistic fireball and material assumed to be still located just outside the progenitor star. Only a small fraction of the expected mass is sufficient to efficiently decelerate the fireball, leading to dissipation of most of its kinetic energy. Since the scattering optical depths are still large at distances comparable to the progenitor radius, the dissi...