Ten per cent polarized optical emission from GRB090102
Abstract
The nature of the jets and the role of magnetic fields in gamma-ray bursts (GRBs) remains unclear. In a baryon-dominated jet only weak, tangled fields generated in situ through shocks would be present. In an alternative model, jets are threaded with large-scale magnetic fields that originate at the central engine and that accelerate and collimate the material. To distinguish between the models the degree of polarization in early-time emission must be measured; however, previous claims of gamma-ray polarization have been controversial. Here we report that the early optical emission from GRB090102 was polarized at 10+/-1 per cent, indicating the presence of large-scale fields originating in the expanding fireball. If the degree of polarization and its position angle were variable on timescales shorter than our 60-second exposure, then the peak polarization may have been larger than ten per cent.
- Publication:
-
Nature
- Pub Date:
- December 2009
- DOI:
- 10.1038/nature08590
- arXiv:
- arXiv:1010.1255
- Bibcode:
- 2009Natur.462..767S
- Keywords:
-
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 16 pages, 4 figures. Published in Nature (2009), Vol. 462, p767-769