Collective spectra ofthe resonant inverse Compton scattering ofthe assembly of relativistic electrons in an intense magnetic field

• 1、Institute of Nuclear, Particle, Astronomy andCosmology, Department of Physics, Shanghai Jiao Tong University
• 2、 Department of Astronomy, Nanjing University, Nanjing 210093
• 3、 Institute of Cosmic Ray, Department of Physics, College of Science, Tibet University, Lhasa 850000

Abstract：The resonant inverse Compton scattering (RICS) of relativistic electrons inan intense magnetic field of a neutron star is an efficient mechanism forproducing the high-energy $gamma$-rays due to its high efficiency, high frequency,highly beaming behaviour and comparatively good monochromaticity, concentrating mostradiation in the high-frequency band(hard X-ray and $gamma$-ray). In our previous work,we argued that thedominant radiation mechanism responsible for the prompt $gamma$-ray emissionof gamma-ray bursts in the early stage could be the resonant inverse Compton scattering of relativisticelectrons. By using this mechanism, some puzzles in the study of gamma-ray bursts couldbe clarified, e.g., the origin of the Amati relation, the formation of the observedbroken power-law spectra, the related deadline problem, and the polarization property, etc.The simplified analyticalformulae of collective RICS spectra of the resonant inverse Compton scattering forassembly of relativistic electrons in an intense magnetic field are derived in this paper, based on thesimple RICS spectral power of a single fast electron given in our previous paper. By using theseformulae, a series of collective RICS spectra for various typical ambientlow-frequency radiation fields around the central neutron star are calculated, e.g.the black body radiation, the nonthermal field with power law form spectrum, andthe bremsstrahlung field. The collective RICS spectra are all in quite simpleanalytical expressions, which is convenient for comparison with the observed spectra.Our calculations show that the RICS process is really a very efficient radiation mechanismin the hard X-ray and $gamma$-ray bands if the `accommodation condition' (or the `matching condition')is satisfied. Our calculation shows that various collective RICS spectra havecommon broken power-law forms with different power-indices in the low- and high-frequency bands respectively,despite what kind of ambient soft-photon field is related. Finally, we discussthe potential applications of RICS mechanism in high-energy astrophysics, i.e., in the explorations oforigin of radiation in the gamma-ray bursts(GRBs), soft gamma-ray repeaters(SGRs) andgamma-ray pulsars(GRPs), etc.

Keywords： High-energy astrophysics radiation mechanism: non-thermal --- methods:analytical --- gamma-rays: general