1999/06/29 by G. Ghisellini, Gabriele Ghisellini, Davide Lazzati +1 · 9 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Brewster's angle #Collimated light #Degree of polarization #Gamma-ray burst #Gamma-ray bursts and supernovae #Light curve #Linear polarization #Lorentz factor #Polarization (electrochemistry) #Position angle #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.1999.03025.x
5 pages, 4 postscript figures, submitted to MNRAS letters
arxiv created 1999/06/29 · openalex publication_date 1999/10/11 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The recently detected linear polarization in the optical light curve of GRB 990510 renewed interest in how polarization can be produced in gamma-ray burst fireballs. Here we present a model based on the assumption that we are seeing a collimated fireball, observed slightly off-axis. This introduces some degree of anisotropy, and makes it possible to observe a linearly polarized flux even if the magnetic field is completely tangled in the plane orthogonal to the line of sight. We construct the light curve of the polarization flux, showing that it is always characterized by two maxima, with the polarization position angle changing by 90° between the first and the second maximum. The very same geometry as assumed here implies that the total flux initially decays in time as a power law, but gradually steepens as the bulk Lorentz factor of the fireball decreases.