2014/02/28 by Paz Beniamini, Tsvi Piran · 1 citation
Physics and Astronomy · #Acceleration #Active galactic nucleus #Astrophysical Phenomena and Observations #Astrophysical jet #Astrophysics #Electron #Flux (metallurgy) #Galaxy #Gamma-ray burst #Gamma-ray bursts and supernovae #Lorentz factor #Lorentz transformation #Magnetic field #Nuclear physics #Physics #Poynting vector #Pulsars and Gravitational Waves Research #Synchrotron #Synchrotron radiation #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stu2032
30 pages, 10 figures
arxiv created 2014/06/06 · openalex publication_date 2014/10/31 · arxiv updated 2015/06/18 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We consider the conditions within a Poynting-flux-dominated gamma-ray burst (GRB) emission region. Because of the enormous magnetic energy density, relativistic electrons will cool in such a region extremely rapidly via synchrotron. As there is no known mechanism that can compete in these magnetic environments with synchrotron it must be the source of the prompt sub-MeV emission. This sets strong limits on the size and Lorentz factor of the outflow. Furthermore, synchrotron cooling is too efficient. It overproduces optical and X-ray as compared with the observations. This overproduction of low-energy emission can be avoided if the electrons are re-accelerated many times (≳ 5 × 104) during each pulse (or are continuously heated) or if they escape the emitting region before cooling down. We explore the limitations of both models practically ruling out the later and demonstrating that the former requires two different acceleration mechanisms as well as an extremely large magnetic energy to Baryonic energy ratio. To be viable, any GRB model based on an emission region that is Poynting flux dominated must demonstrate how these conditions are met. We conclude that if GRB jets are launched magnetically dominated they must dissipate somehow most of their magnetic energy before they reach the emission region.