Reverse Shock Emission in an Off-axis Top-hat Jet Model for Gamma-Ray Bursts
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arXiv
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| Format: | Preprint |
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2024
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| author | Pang, Sen-Lin Dai, Zi-Gao |
| author_facet | Pang, Sen-Lin Dai, Zi-Gao |
| contents | The afterglow of a gamma-ray burst (GRB) has been widely argued to arise from the interaction of a relativistic outflow with its ambient medium. During such an interaction, a pair of shocks are generated: a forward shock that propagates into the medium, and a reverse shock that propagates into the outflow. Extensive studies have been conducted on the emission from the forward shock viewed off-axis. Furthermore, the observation of a reverse shock in an on-axis short GRB suggests that the reverse shock can produce an electromagnetic counterpart to a gravitational wave-detected merger. In this paper, we investigate the contribution of the reverse shock to the afterglow from a top-hat jet viewed off-axis, and apply our model to some short GRBs previously modeled by an off-axis emission. We employ the Markov Chain Monte Carlo (MCMC) method to get the model parameters (i.e., the jet's half-opening angle $θ_j$, the viewing angle $θ_\text{obs}$, the initial Lorentz factor $Γ_0$, and the isotropic energy $E_\mathrm{iso}$). Our model successfully reproduces off-axis afterglow emission without a structured jet. In addition, our calculations suggest that the reverse shock may produce a prominent feature in an early afterglow, which can be potentially observed in an orphan optical afterglow. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_17224 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Reverse Shock Emission in an Off-axis Top-hat Jet Model for Gamma-Ray Bursts Pang, Sen-Lin Dai, Zi-Gao High Energy Astrophysical Phenomena The afterglow of a gamma-ray burst (GRB) has been widely argued to arise from the interaction of a relativistic outflow with its ambient medium. During such an interaction, a pair of shocks are generated: a forward shock that propagates into the medium, and a reverse shock that propagates into the outflow. Extensive studies have been conducted on the emission from the forward shock viewed off-axis. Furthermore, the observation of a reverse shock in an on-axis short GRB suggests that the reverse shock can produce an electromagnetic counterpart to a gravitational wave-detected merger. In this paper, we investigate the contribution of the reverse shock to the afterglow from a top-hat jet viewed off-axis, and apply our model to some short GRBs previously modeled by an off-axis emission. We employ the Markov Chain Monte Carlo (MCMC) method to get the model parameters (i.e., the jet's half-opening angle $θ_j$, the viewing angle $θ_\text{obs}$, the initial Lorentz factor $Γ_0$, and the isotropic energy $E_\mathrm{iso}$). Our model successfully reproduces off-axis afterglow emission without a structured jet. In addition, our calculations suggest that the reverse shock may produce a prominent feature in an early afterglow, which can be potentially observed in an orphan optical afterglow. |
| title | Reverse Shock Emission in an Off-axis Top-hat Jet Model for Gamma-Ray Bursts |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2402.17224 |