Polarization of Prompt Gamma-Ray Burst Emission: Evidence for Electromagnetically Dominated Outflow

By M. Lyutikov, V. Pariev, Roger Blandford McGill University Cita, U. O. C. E. F. Institute, C. I. O. Technology.. 2003

205 citations recorded by the source corpus.

Observations by the RHESSI satellite of the large polarization of the prompt γ-ray emission from γ-ray burst (GRB) 021206 imply that the magnetic field coherence scale is larger than the size of the visible emitting region, ~R/Γ, where R is the radius of the flow and Γ is the associated Lorentz factor. Such fields cannot be generated in a causally disconnected, hydrodynamically dominated outflow. Electromagnetic models of GRBs, in which large-scale, dynamically dominant, magnetic fields are present in the outflow from the very beginning, provide a natural explanation of this large reported linear polarization. We derive the Stokes parameters of the synchrotron emission of a relativistically moving plasma with a given magnetic field configuration and calculate the pulse-averaged polarization fraction of the emission from a relativistically expanding shell carrying a global toroidal magnetic field. For viewing angles larger than 1/Γ, the observed patch of the emitting shell has an almost homogeneous magnetic field, producing a large fractional polarization (56% for a power-law energy distribution of relativistic particles, dn/dϵ ∝ ϵ-3). The maximum polarization is smaller than the theoretical upper limit for a stationary plasma in a uniform magnetic field because of relativistic kinematic effects.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e6e86bdbb1e61f449ed7df3fb3366f4a9074b028

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In Astronomy and Astrophysics

Citations in the corpus

THE INTERNAL-COLLISION-INDUCED MAGNETIC RECONNECTION AND TURBULENCE (ICMART) MODEL OF GAMMA-RAY BURSTS (2010, background): “The initial gamma-ray polarization degree may be close to the maximum value achievable for synchrotron emission in an ordered magnetic field, i.e. Π ∼ 50% − 60% (Lyutikov et al. 2003; Granot 2003).”
The Supernova Gamma-Ray Burst Connection (2006, methodology): “In the model developed by Lyutikov and Blandford, the GRB emission comes from 1016 cm not 1013 cm. Poynting flux models have the capability of producing large polarization (Lyutikov et al., 2003) which might be a diagnostic of the model.”
DETECTION OF GAMMA-RAY POLARIZATION IN PROMPT EMISSION OF GRB 100826A (2011, background): “…magnetic field structure (for reviews, Lazzati 2006; Toma et al. 2009); (a) synchrotron in globally ordered toroidal field (SO model; Granot 2003; Lyutikov et al. 2003; Zhang & Yan 2011), (b) in random fields on plasma skin depth scales (SR model; Granot 2003; Nakar et al. 2003), and (c) in…”
TURBULENT, EXTREME MULTI-ZONE MODEL FOR SIMULATING FLUX AND POLARIZATION VARIABILITY IN BLAZARS (2013, background): “…transforms the upstream field to the standing shock frame (which is the same as the rest frame of the host galaxy), applies the compression factor to the component perpendicular to the shock normal, and then transforms the field to the rest frame of the downstream plasma (see Lyutikov et al. 2003).”