GRB jet structure and the jet break
| Autor: | Lamb, Gavin P, Kann, D. Alexander, Fernández, Joseph John, Mandel, Ilya, Levan, Andrew J., Tanvir, Nial R. |
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| Rok vydání: | 2021 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/mnras/stab2071 |
| Popis: | We investigate the shape of the jet break in within-beam gamma-ray burst (GRB) optical afterglows for various lateral jet structure profiles. We consider cases with and without lateral spreading and a range of inclinations within the jet core half-opening angle, $\theta_c$. We fit model and observed afterglow lightcurves with a smoothly-broken power-law function with a free-parameter $\kappa$ that describes the sharpness of the break. We find that the jet break is sharper ($\kappa$ is greater) when lateral spreading is included than in the absence of lateral spreading. For profiles with a sharp-edged core, the sharpness parameter has a broad range of $0.1\lesssim\kappa\lesssim4.6$, whereas profiles with a smooth-edged core have a narrower range of $0.1\lesssim\kappa\lesssim2.2$ when models both with and without lateral spreading are included. For sharp-edged jets, the jet break sharpness depends strongly on the inclination of the system within $\theta_c$, whereas for smooth-edged jets, $\kappa$ is more strongly dependent on the size of $\theta_c$. Using a sample of 20 GRBs we find nine candidate smooth-edged jet structures and eight candidate sharp-edged jet structures, while the remaining three are consistent with either. The shape of the jet break, as measured by the sharpness parameter $\kappa$, can be used as an initial check for the presence of lateral structure in within-beam GRBs where the afterglow is well-sampled at and around the jet-break time. Comment: 13 pages, 5 figures, accepted for publication in MNRAS 15/07/21 |
| Databáze: | arXiv |
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