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 $\sim 1$\% of equipartition, in agreement with theoretical expectations of a micro-turbulence 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 micro-turbulence 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 micro-turbulence. It calculates the expected temporal and spectral indices $\alpha$ and $\beta$ customarily defined by $F_{\nu }\propto t_{\mathrm{obs}}^{-\alpha }{\nu }^{-\beta }$ 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.

13 pages, 6 figures, to appear in MNRAS

References in corpus (14)

• Particle acceleration in relativistic collisionless shocks: Fermi process at last?
• On the structure of relativistic collisionless shocks in electron-ion plasmas
• Klein-Nishina Effects on Optically Thin Synchrotron and Synchrotron Self-Compton Spectrum
• Long Term Evolution of Magnetic Turbulence in Relativistic Collisionless Shocks: Electron-Positron Plasmas
• Magnetic field evolution in relativistic unmagnetized collisionless shocks
• On the efficiency of Fermi acceleration at relativistic shocks
• On Fermi acceleration and MHD-instabilities at ultra-relativistic magnetized shock waves
• Cosmic-Ray Acceleration at Ultrarelativistic Shock Waves: Effects of Downstream Short-Wave Turbulence
• Clustering of LAT light curves: a clue to the origin of high-energy emission in Gamma-Ray Bursts
• Synchrotron emission in the fast cooling regime: which spectra can be explained?
• Constraints on Very High Energy Emission from GRB 130427A
• Non-linear collisionless damping of Weibel turbulence in relativistic blast waves
• Current-driven filamentation upstream of magnetized relativistic collisionless shocks
• A fast current-driven instability in relativistic collisionless shocks

Cited by in corpus (13)

• Observation of inverse Compton emission from a long $\gamma$-ray burst
• High-energy emission from Gamma-Ray Bursts
• Towards understanding the physics of collisionless relativistic shocks
• GRB afterglow parameters in the era of TeV observations: the case of GRB~190114C
• Off-axis jet scenario for early afterglow emission of low-luminosity gamma-ray burst GRB 190829A
• Physics and phenomenology of weakly magnetized, relativistic astrophysical shock waves
• Closure relations of Gamma Ray Bursts in high energy emission
• Modeling Synchrotron Self-Compton and Klein-Nishina Effects in Gamma-Ray Burst Afterglows
• A VLA Study of High-redshift GRBs I - Multi-wavelength Observations and Modeling of GRB 140311A
• Physical origin of GeV emission in the early phase of GRB 170405A: Clues from emission onsets with multi-wavelength observations
• Time dependent numerical model for the very high energy emissions of distant gamma-ray busrt GRB 201216C
• The elusive synchrotron precursor of collisionless shocks
• Searching for an additional high-energy component in Fermi-LAT GRB afterglows