主要内容:
同步辐射低能段是1/3，光子指数是-2/3.如果比-2/3还小，那就没办法解释了（如果大于-2/3还可以，说有黑体成分，因为黑体的低能段是1）。这篇文章说考虑一下IC，就可以了？没看懂，不知道他说的steeper是相对什么陡。
他还扯到了同步辐射快冷却的-1/2，光子指数是-3/2.
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文章信息:
- · arXiv e-print (arXiv:1009.2636)
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| Title: |
| Reconciling observed GRB prompt spectra with synchrotron radiation ? |
| Authors: |
| Daigne, F.; Bosnjak, Z.; Dubus, Guillaume |
| Publication: |
| eprint arXiv:1009.2636 |
| Publication Date: |
| 09/2010 |
| Origin: |
| ARXIV |
| Keywords: |
| Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics |
| Comment: |
| 14 pages, 10 figures, submitted for publication in A&A |
| Bibliographic Code: |
| 2010arXiv1009.2636D |
Abstract
(abridged) Prompt GRB emission is often interpreted as synchrotron radiation from high-energy electrons accelerated in internal shocks. Fast synchrotron cooling leads to the prediction that the slope below the spectral peak has a photon index alpha=-3/2. However, this differs significantly from the observed median value alpha~-1. We quantify the influence of inverse Compton and adiabatic cooling on alpha to understand whether these processes can reconcile the observations with a synchrotron origin. We use a time-dependent code developed to calculate the GRB prompt emission within the internal shock model. The code follows both the shock dynamics and electron energy losses and can generate lightcurves and spectra. We investigate the dependence of the low-energy slope on the parameters of the model. Slopes between -3/2 and -1 are reached when electrons suffer IC losses in the Klein-Nishina regime. This does not necessarily imply a strong IC component in the Fermi/LAT range because scatterings are only moderately efficient. Steep slopes require that a large fraction (10-30%) of the dissipated energy is given to a small fraction (<~ 1%) of the electrons and that the magnetic field energy density fraction remains low (<~ 0.1%). Values of alpha up to -2/3 can be obtained with relatively high radiative efficiencies (>50%) when adiabatic cooling is comparable with radiative cooling (marginally fast cooling). This requires collisions at small radii and/or with low magnetic fields. Amending the standard fast cooling scenario to account for IC cooling naturally leads to alpha up to -1. Marginally fast cooling may also account for alpha up to -2/3, although the conditions required are more difficult to reach. Still, the majority of observed GRB prompt spectra can be reconciled with a synchrotron origin, constraining the microphysics of mildly relativistic internal shocks.
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