Open AccessOverall temporal synchrotron emissions from relativistic jets: adiabatic and radiative breaks
Author(s) -
Li Zhuo,
Dai Z. G.,
Lu T.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05141.x
Subject(s) - physics , adiabatic process , radiative transfer , jet (fluid) , afterglow , electron , radiative cooling , synchrotron , astrophysical jet , astrophysics , light curve , compton scattering , synchrotron radiation , gamma ray burst , nuclear physics , active galactic nucleus , optics , quantum mechanics , mechanics , galaxy
We discuss the afterglow emission from a relativistic jet that is initially in the radiative regime, in which the accelerated electrons are fast‐cooling. We note that such a ‘semiradiative’ jet decelerates faster than an adiabatic jet does. We also take into account the effect of strong inverse‐Compton scattering on the cooling frequency in the synchrotron component and therefore on the light‐curve decay index. We find that there are two kinds of light‐curve break for the jet effect. The first is an ‘adiabatic break’, if the electrons become slow‐cooling before the jet enters a spreading phase, and the second is a ‘radiative break’, which appears in the contrary case. We then show how a relativistic jet evolves dynamically and derive the overall temporal synchrotron emission in both cases, focusing on the change in the light‐curve decay index around the break time. Finally, in view of our results, we rule out two cases for relativistic jets which do not account for the observed light‐curve breaks in a few afterglows: (i) an adiabatic jet with strong Compton cooling ( Y >1) and with the cooling frequency ν c locating in the observed energy range; (ii) a radiative jet with a significant fraction of total energy occupied by electrons ( ε e ∼1) .