'Late prompt' emission in Gamma Ray Bursts?
| Autor: | Gabriele Ghisellini, Giancarlo Ghirlanda, C. Firmani, Lara Nava |
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| Rok vydání: | 2007 |
| Předmět: |
Physics
Jet (fluid) Lorentz transformation Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) Phase (waves) FOS: Physical sciences Astronomy and Astrophysics Astrophysics Dissipation Light curve Plateau (mathematics) Afterglow symbols.namesake Space and Planetary Science symbols Gamma-ray burst |
| Zdroj: | Scopus-Elsevier |
| DOI: | 10.48550/arxiv.astro-ph/0701430 |
| Popis: | The flat decay phase in the first 1e2-1e4 seconds of the X-ray light curve of Gamma Ray Bursts (GRBs) has not yet found a convincing explanation. The fact that the optical and X-ray lightcurves are often different, with breaks at different times, makes contrived any explanation based on the same origin for both the X-ray and optical fluxes. We here assume that the central engine can be active for a long time, producing shells of decreasing bulk Lorentz factors Gamma. We also assume that the internal dissipation of these late shells produces a continuous and smooth emission (power-law in time), usually dominant in X-rays and sometimes in the optical. When Gamma of the late shells is larger than 1/theta_j, where theta_j is the jet opening angle, we see only a portion of the emitting surface. Eventually, Gamma becomes smaller than 1/theta_j, and the entire emitting surface is visible. Thus there is a break in the light curve when Gamma=1/theta_j, which we associate to the time at which the plateau ends. After the steeply decaying phase which follows the early prompt, we see the sum of two emission components: the "late-prompt" emission (due to late internal dissipation), and the "real afterglow" emission (due to external shocks). A variety of different optical and X-ray light curves are then possible, explaining why the X-ray and the optical light curves often do not track each other (but sometimes do), and often they do not have simultaneous breaks. Comment: Accepted for publication in ApJ Letters |
| Databáze: | OpenAIRE |
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