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Prompt GRB polarization from non-axisymmetric jets.
- Source :
-
Monthly Notices of the Royal Astronomical Society . Feb2024, Vol. 527 Issue 4, p12178-12195. 18p. - Publication Year :
- 2024
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Abstract
- Time-resolved linear polarization (Π) measurements of the prompt gamma-ray burst emission can reveal its dominant radiation mechanism. A widely considered mechanism is synchrotron radiation, for which linear polarization can be used to probe the jet's magnetic-field structure, and in turn its composition. In axisymmetric jet models, the polarization angle (PA) can only change by 90°, as Π temporarily vanishes. However, some time-resolved measurements find a continuously changing PA, which requires the flow to be non-axisymmetric in at least one out of its emissivity, bulk Lorentz factor, or magnetic field. Here, we consider synchrotron emission in non-axisymmetric jets, from an ultrarelativistic thin shell, comprising multiple radially expanding mini-jets (MJs) or emissivity patches within the global jet, that yield a continuously changing PA. We explore a wide variety of possibilities with emission consisting of a single pulse or multiple overlapping pulses, presenting time-resolved and integrated polarization from different magnetic field configurations and jet angular structures. We find that emission from multiple incoherent MJs/patches reduces the net polarization due to partial cancellation in the Stokes plane. When these contain a large-scale ordered field in the plane transverse to the radial direction, Π always starts near maximal and then declines over the single pulse or shows multiple highly polarized peaks due to multiple pulses. Observing |$\Pi \lesssim 40~{{\ \rm per\ cent}}$| (15  per cent) integrated over one (several) pulse(s) will instead favour a shock-produced small-scale field either ordered in the radial direction or tangled in the plane transverse to it. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 527
- Issue :
- 4
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 175011060
- Full Text :
- https://doi.org/10.1093/mnras/stad3991