@Article{GuiriecKDZHNTBGGKMMRRRU:2015:NeMoGR,
author = "Guiriec, S. and Kouvelitou, C. and Daigne, F. and Zhang, B. and
Hascoet, R. and Nemmen, R. S. and Thompson, D. J. and Bhat, P. N.
and Gehrels, S. and Gonzalez, M. M. and Kaneko, Y. and McEnery, J.
and Mochkovitch, R. and Racusin, J. L. and Ryde, F. and Reyes,
Jos{\'e} Rodrigo Sacahui and Unsal, A. M.",
affiliation = "NASA and NASA and {} and {} and {} and {} and NASA and {} and NASA
and {} and {} and NASA and {} and NASA and {} and {Instituto
Nacional de Pesquisas Espaciais (INPE)}",
title = "Toward a better understanding of the GRB phenomenon: a new model
for GRB prompt emission and its effects of the new
L-i(NT)-E-peak,i(rest,NT) relation",
journal = "Astrophysical Journal",
year = "2015",
volume = "807",
number = "2",
month = "July",
keywords = "acceleration of particles, black hole physics, distance scale,
gamma-ray burst: general, radiation mechanisms: non-thermal,
radiation mechanisms: thermal.",
abstract = "Gamma-ray burst (GRB) prompt emission spectra in the keV-MeV
energy range are usually considered to be adequately fitted with
the empirical Band function. Recent observations with the Fermi
Gamma-ray Space Telescope (Fermi) revealed deviations from the
Band function, sometimes in the form of an additional blackbody
(BB) component, while on other occasions in the form of an
additional power law (PL) component extending to high energies. In
this article we investigate the possibility that the three
components may be present simultaneously in the prompt emission
spectra of two very bright GRBs (080916C and 090926A) observed
with Fermi, and how the three components may affect the overall
shape of the spectra. While the two GRBs are very different when
fitted to a single Band function, they look like {"}twins{"} in
the three-component scenario. Through fine-time spectroscopy down
to the 100 ms timescale, we follow the evolution of the various
components. We succeed in reducing the number of free parameters
in the three-component model, which results in a new
semi-empirical model-but with physical motivations-to be
competitive with the Band function in terms of number of degrees
of freedom. From this analysis using multiple components, the Band
function is globally the most intense component, although the
additional PL can overpower the others in sharp time structures.
The Band function and the BB component are the most intense at
early times and globally fade across the burst duration. The
additional PL is the most intense component at late time and may
be correlated with the extended high-energy emission observed
thousands of seconds after the burst with Fermi/Large Area
Telescope. Unexpectedly, this analysis also shows that the
additional PL may be present from the very beginning of the burst,
where it may even overpower the other components at low energy. We
investigate the effect of the three components on the new
time-resolved luminosity-hardness relation in both the observer
and rest frames and show that a strong correlation exists between
the flux of the non-thermal Band function and its E-peak only when
the three components are fitted simultaneously to the data (i.e.,
F-i(NT)-E-peak,i(NT) relation). In addition, this result points
toward a universal relation between those two quantities when
transposed to the central engine rest frame for all GRBs (i.e.,
L-i(NT)-E-peak,i(rest,NT) relation). We discuss a possible
theoretical interpretation of the three spectral components within
this new empirical model. We suggest that (i) the BB component may
be interpreted as the photosphere emission of a magnetized
relativistic outflow, (ii) the Band component has synchrotron
radiation in an optically thin region above the photosphere,
either from internal shocks or magnetic field dissipation, and
(iii) the extra PL component extending to high energies likely has
an inverse Compton origin of some sort, even though its extension
to a much lower energy remains a mystery.",
doi = "10.1088/0004-637X/807/2/148",
url = "http://dx.doi.org/10.1088/0004-637X/807/2/148",
issn = "0004-637X and 1538-4357",
language = "en",
urlaccessdate = "02 maio 2024"
}