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The synchrotron self-Compton spectrum of relativistic blast waves at large Y

Abstract : Recent analyses of multiwavelength light curves of gamma-ray bursts afterglows point to values of the magnetic turbulence well below the canonical ∼1 per cent of equipartition, in agreement with theoretical expectations of a microturbulence generated in the shock precursor, which then decays downstream of the shock front through collisionless damping. As a direct consequence, the Compton parameter Y can take large values in the blast. In the presence of decaying microturbulence and/or as a result of the Klein-Nishina suppression of inverse Compton cooling, the Y parameter carries a non-trivial dependence on the electron Lorentz factor, which modifies the spectral shape of the synchrotron and inverse Compton components. This paper provides detailed calculations of this synchrotron self-Compton spectrum in this large Y regime, accounting for the possibility of decaying microturbulence. It calculates the expected temporal and spectral indices α and β customarily defined by F_ν ∝ t_obs^{-α }ν ^{-β } in various spectral domains. This paper also makes predictions for the very high energy photon flux; in particular, it shows that the large Y regime would imply a detection rate of gamma-ray bursts at >10 GeV several times larger than currently anticipated.
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Submitted on : Monday, April 25, 2022 - 11:09:59 AM
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Martin Lemoine. The synchrotron self-Compton spectrum of relativistic blast waves at large Y. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2015, 453, pp.3772-3784. ⟨10.1093/mnras/stv1800⟩. ⟨insu-03644696⟩



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