Spectral and polarization properties of photospheric emission from stratified jets

Hirotaka Ito, Shigehiro Nagataki, Jin Matsumoto, Shiu Hang Lee, Alexey Tolstov, Jirong Mao, Maria Dainotti, Akira Mizuta

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


We explore the spectral and polarization properties of photospheric emissions from stratified jets in which multiple components, separated by sharp velocity shear regions, are distributed in lateral directions. Propagation of thermal photons injected at a high optical depth region are calculated until they escape from the photosphere. It is found that the presence of the lateral structure within the jet leads to the nonthermal feature of the spectra and significant polarization signal in the resulting emission. The deviation from thermal spectra, as well as the polarization degree, tends to be enhanced as the velocity gradient in the shear region increases. In particular, we show that emissions from multicomponent jet can reproduce the typical observed spectra of gamma-ray bursts irrespective of the position of the observer when a velocity shear region is closely spaced in various lateral (θ) positions. The degree of polarization associated with the emission is significant (>few percent) at a wide range of observer angles and can be higher than 30%.

Original languageEnglish
Article number159
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2014 Jul 10
Externally publishedYes


  • gamma-ray burst: general
  • radiation mechanisms: thermal
  • radiative transfer
  • scattering

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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