Early optical polarization of a gamma-ray burst afterglow

Carole G. Mundell, Iain A. Steels, Robert J. Smith, Shiho Kobayashi, Andrea Melandri, Cristiano Guidorzi, Andreja Gomboc, Chris J. Mottram, David Clarke, Alessandro Monfardini, David Carter, David Bersier

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Abstract

We report the optical polarization of a gamma-ray burst (GRB) afterglow, obtained 203 seconds after the initial burst of γ-rays from GRB 060418, using a ring polarimeter on the robotic Liverpool Telescope. Our robust (2σ) upper limit on the percentage of polarization, less than 8%, coincides with the fireball deceleration time at the onset of the afterglow. The combination of the rate of decay of the optical brightness and the low polarization at this critical time constrains standard models of GRB ejecta, ruling out the presence of a large-scale ordered magnetic field in the emitting region.

Original languageEnglish
Pages (from-to)1822-1824
Number of pages3
JournalScience
Volume315
Issue number5820
DOIs
Publication statusPublished - 30 Mar 2007

ASJC Scopus subject areas

  • General

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    Mundell, C. G., Steels, I. A., Smith, R. J., Kobayashi, S., Melandri, A., Guidorzi, C., Gomboc, A., Mottram, C. J., Clarke, D., Monfardini, A., Carter, D., & Bersier, D. (2007). Early optical polarization of a gamma-ray burst afterglow. Science, 315(5820), 1822-1824. https://doi.org/10.1126/science.1138484