GAMMA-RAY BURSTS: DECELERATION AND PROMPT EMISSION
Chris Thompson (CITA/Univ of Toronto) - 24 Apr at 12:00 noon
One of the `unsolved mysteries' of gamma-ray bursts is the
mechanism responsible for the prompt emission. This talk
will consider several aspects of the dynamics and radiation
properties of a relativistic, magnetized outflow of the
requisite luminosity ($\sim 10^{50}$ erg/s total). I will
argue that fireball radiation that is created near the
breakout point of a relativistic jet from a Wolf-Rayet star
plays a significant role the subsequent acceleration of the
jet material, and in regulating the peak frequency of the
prompt gamma-ray spectrum. The observed `Amati relation'
of long GRBs is most easily explained if the heating of
electrons (and positrons) is spatially distributed within
the flow. Particular attention will be given to the damping of
MHD motions: when the magnetic energy density dominates the
rest energy density in the light charges, particle heating
occurs primarily by electrostatic acceleration. Inverse
Compton cooling off the seed fireball photons at $\sim 10^{15}$ cm
offers a simple explanation for the observed relation between
gamma-ray pulse width and photon frequency. The relativistic
outflow eventually decelerates through its interaction with
the Wolf-Rayet wind material and a thin shell that
is entrained during jet breakout. Pair creation in the
ambient medium can delay the deceleration and help to regulate
the radiative compactness of the prompt emission zone.
The seminar will be held in 544 Campbell Hall.
Return to seminar schedule