Fast-cooling synchrotron radiation in a decaying magnetic field and γ-ray burst emission mechanism

By Z. L. Uhm, Bing Zhang. Nature Physics, 2013

177 citations recorded by the source corpus.

Gamma-ray bursts are among the most luminous explosions in the cosmos, but the mechanism behind the energetic radiation remains unclear. ‘Fast cooling’ electrons in a decaying magnetic field may offer an explanation. Synchrotron radiation of relativistic electrons is an important radiation mechanism in many astrophysical sources. In the sources where the synchrotron cooling timescale is shorter than the dynamical timescale, electrons are cooled down below the minimum injection energy. It has been believed that such ‘fast cooling’ electrons have a power-law distribution in energy with an index −2, and their synchrotron radiation has a photon spectral index1−1.5. On the other hand, in a transient expanding astrophysical source, such as a γ-ray burst (GRB), the magnetic field strength in the emission region continuously decreases with radius. Here we study such a system, and find that in a certain parameter regime, the fast-cooling electrons can have a harder energy spectrum. We apply this new physical regime to GRBs, and suggest that the GRB prompt emission spectra whose low-energy photon spectral index has a typical value2,3,4,5−1 could be due to synchrotron radiation in this moderately fast-cooling regime.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/fc16ef3dce9d70b53858d0ee8f89bde1211343fd

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In Astronomy and Astrophysics

  1. Pawan Kumar
  2. Bing Zhang
  3. E. Liang
  4. B. Metzger
  5. E. Nakar
  6. P. Mészáros
  7. Binbin Zhang
  8. Xuefeng Wu

In Nuclear and High Energy Physics

  1. Bing Zhang
  2. Pawan Kumar
  3. E. Berger

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