TY - JOUR
TI - A marginally fast-cooling proton-synchrotron model for prompt GRBs
AU - Florou, Ioulia
AU - Petropoulou, Maria
AU - Mastichiadis, Apostolos
JO - Monthly Notices of the Royal Astronomical Society
PY - 2021
VL - 505
TODO - 1
SP - 1367-1381
PB - Oxford University Press
SN - 0035-8711, 1365-2966
TODO - 10.1093/mnras/stab1285
TODO - neutrinos; radiation mechanisms: non-thermal; gamma-ray burst: general
TODO - A small fraction of gamma-ray bursts (GRBs) with available data down to
soft X-rays (similar to 0.5 keV) has been shown to feature a spectral
break in the low-energy part (similar to 1-10 keV) of their prompt
emission spectrum. The overall spectral shape is consistent with
optically thin synchrotron emission from a population of particles that
have cooled on a time-scale comparable to the dynamic time to energies
that are still much higher than their rest-mass energy (marginally fast
cooling regime). We consider a hadronic scenario and investigate if the
prompt emission of these GRBs can originate from relativistic protons
that radiate synchrotron in the marginally fast cooling regime. Using
semi-analytical methods, we derive the source parameters, such as
magnetic field strength and proton luminosity, and calculate the
high-energy neutrino emission expected in this scenario. We also
investigate how the emission of secondary pairs produced by photopion
interactions and gamma gamma pair production affect the broad-band
photon spectrum. We support our findings with detailed numerical
calculations. Strong modification of the photon spectrum below the break
energy due to the synchrotron emission of secondary pairs is found,
unless the bulk Lorentz factor is very large (Gamma greater than or
similar to 10(3)). Moreover, this scenario predicts unreasonably high
Poynting luminosities because of the strong magnetic fields (10(6)-10(7)
G) that are necessary for the incomplete proton cooling. Our results
strongly disfavour marginally fast cooling protons as an explanation of
the low-energy spectral break in the prompt GRB spectra.
ER -