Diffusive photospheres in gamma-ray bursts. (arXiv:2003.11440v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Vereshchagin_G/0/1/0/all/0/1">G. V. Vereshchagin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Siutsou_I/0/1/0/all/0/1">I. A. Siutsou</a>
Photospheric emission may originate from relativistic outflows in two
qualitatively different regimes: last scattering of photons inside the outflow
at the photospheric radius, or radiative diffusion to the boundary of the
outflow. In this work the measurement of temperature and flux of the thermal
component in the early afterglows of several gamma-ray bursts (GRBs) along with
the total flux in the prompt phase are used to determine initial radii of the
outflow as well as its Lorentz factors. Results indicate that in some cases the
outflow has relatively low Lorentz factors $Gamma<10$, favouring cocoon
interpretation, while in other cases Lorentz factors are larger $Gamma>10$,
indicating diffusive photospheric origin of the thermal component, associated
with an ultrarelativistic outflow.
Photospheric emission may originate from relativistic outflows in two
qualitatively different regimes: last scattering of photons inside the outflow
at the photospheric radius, or radiative diffusion to the boundary of the
outflow. In this work the measurement of temperature and flux of the thermal
component in the early afterglows of several gamma-ray bursts (GRBs) along with
the total flux in the prompt phase are used to determine initial radii of the
outflow as well as its Lorentz factors. Results indicate that in some cases the
outflow has relatively low Lorentz factors $Gamma<10$, favouring cocoon
interpretation, while in other cases Lorentz factors are larger $Gamma>10$,
indicating diffusive photospheric origin of the thermal component, associated
with an ultrarelativistic outflow.
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