Gamma-ray burst spectral correlations : Photospheric and injection effects

• We present a physical framework that can account for most of the observed spectral properties of prompt gamma- ray burst emission. This includes the variety of spectral shapes and shape evolutions, and spectral correlations between flux and spectral peaks within bursts, described by Borgonovo & Ryde, and among bursts described by Amati and Ghirlanda. In our proposed model the spectral peak is given by the photospheric emission from a relativistic outflow for which the horizon length is much smaller that the radial width. The observed duration of the thermal flash is given by the radial light- crossing time. This then gives the typical emission site at similar to 10(11) cm with a Lorentz factor of similar to 300. This emission is accompanied by nonthermal emission from dissipation locations outside the photosphere. The relative strengths of these two components depend on injection effects at the central engine, leading to varying relative locations of the saturation and photospheric radii. The total emission can then reproduce the observed variety. The spectral correlations are found by assuming that the amount of energy dissipated depends nonlinearly on the averaged particle density. Besides the spectral correlations, this also gives a description of how the relative strength of the thermal component varies with temperature within a burst.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

gamma rays : bursts

gamma rays : observations

radiation mechanisms : nonthermal

synchrotron shock model

prompt emission

high-energy

evolution

pulses

radiation

acceleration

mechanisms

energetics

bepposax

High energy astrophysics

Publikations- och innehållstyp

ref (ämneskategori)

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