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Flash Heating of Circumstellar Clouds by Gamma-Ray Bursts
The Astrophysical Journal
|May 17, 2000
Summary
Gamma-ray bursts (GRBs) may have their spectra hardened by plasma interactions in circumstellar clouds. This resolves challenges to the synchrotron shock model and suggests observable pair annihilation radiation from past GRB events.
Area of Science:
- Astrophysics
- High-energy astrophysics
- Plasma physics
Background:
- Observations of gamma-ray bursts (GRBs) show harder spectra than predicted by standard optically thin synchrotron emission models.
- The "line-of-death" objection challenges the viability of synchrotron shock models for GRBs.
- Massive star collapse is a leading hypothesis for the origin of GRBs.
Purpose of the Study:
- To propose a mechanism that explains the observed hard spectra of GRBs.
- To reconcile GRB observations with the synchrotron shock model.
- To identify potential observational signatures of past GRB events.
Main Methods:
- Modeling the interaction of intense gamma radiation from GRBs with circumstellar clouds.
- Investigating electron scattering and photon interactions within relativistic plasmas.
- Analyzing the formation and properties of electron-positron pair plasmas.
Main Results:
- Intense gamma radiation from GRBs can rapidly scatter electrons in circumstellar clouds to high energies (hundreds of keV).
- Subsequent scattering of low-energy photons by these hot electrons hardens the intrinsic GRB spectrum.
- This process creates relativistic electron-positron pair plasmas near GRB sources.
Conclusions:
- The proposed plasma interaction mechanism resolves the "line-of-death" objection to the synchrotron shock model for GRBs.
- Electron-positron pair plasmas formed near GRBs are detectable within 1-2 days post-explosion.
- Localized regions of pair annihilation radiation in the Milky Way could serve as evidence of past GRB explosions.