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Gamma-ray bursts afterglows in magnetized stellar winds

Abstract : Recent analytical and numerical work argue that successful relativistic Fermi acceleration requires a weak magnetization of the unshocked plasma, all the more so at high Lorentz factors. The present Letter tests this conclusion by computing the afterglow of a gamma-ray burst outflow propagating in a magnetized stellar wind using 'ab initio' principles regarding the microphysics of relativistic Fermi acceleration. It is shown that in magnetized environments, one expects a drop-out in the X-ray band on subday scales as the synchrotron emission of the shock-heated electrons exits the frequency band. At later times, Fermi acceleration becomes operative when the blast Lorentz factor drops below a certain critical value, leading to the recovery of the standard afterglow light curve. Interestingly, the observed drop-out bears resemblance with the fast decay found in gamma-ray bursts early X-ray afterglows.
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Submitted on : Friday, April 22, 2022 - 3:00:43 PM
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Martin Lemoine, Guy Pelletier. Gamma-ray bursts afterglows in magnetized stellar winds. Monthly Notices of the Royal Astronomical Society: Letters, 2011, 418, pp.L64-L68. ⟨10.1111/j.1745-3933.2011.01144.x⟩. ⟨insu-03645848⟩



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