Early Afterglows in Wind Environments Revisited
Early Afterglows in Wind Environments Revisited
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DOI：
10.1111/j.1365-2966.2005.09411.x
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发表时间：
2005-08
影响因子：
4.8
通讯作者：
Y. Zou;X. Wu;Z. Dai
中科院分区：
文献类型：
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作者：
Y. Zou;X. Wu;Z. Dai
当冷壳层扫过周围介质时，将形成正激波和反激波。我们分析了风环境中的反向-正向冲击，包括它们的动力学和排放。早期的余辉从受冲击的壳层发出，例如可能出现闪光。反向激波在两种近似下表现不同：相对论和牛顿情况，这取决于参数，例如喷出物的初始洛伦兹因子。如果初始洛仑兹因子远小于114 E 1/4 53 −1/4 0，12 A −1/4 <$，−1，则早期的反向激波是牛顿的。这可能发生在较宽的双组分喷流、较低的初始洛伦兹因子引起的孤儿余辉等情况下.同步自吸收效应在牛顿反激波情况下尤为显著，因为吸收频率ν a大于冷却频率ν c和典型参数下的最小同步频率ν m.对于光学到X射线波段，通量在早期几乎不随时间变化，这可能是风环境中喷出物的低初始洛伦兹因子的诊断。我们还研究了不同风密度下的早期光变曲线，并与星际介质模型中的光变曲线进行了比较。Ke yw ords：shock waves-stars：winds，outflows-gamma-rays：bursts.
When a cold shell sweeps up the ambient medium, a forward shock and a reverse shock will form. We analyse the reverse-forward shocks in a wind environment, including their dynamics and emission. An early afterglow is emitted from the shocked shell, e.g. an optical flash may emerge. The reverse shock behaves differently in two approximations: the relativistic and Newtonian cases, which depend on the parameters, e.g. the initial Lorentz factor of the ejecta. If the initial Lorentz factor is much less than 114E 1/4 53 � −1/4 0,12 A −1/4 ∗,−1 , the early reverse shock is Newtonian. This may take place for the wider of a two-component jet, an orphan afterglow caused by a low initial Lorentz factor and so on. The synchrotron self-absorption effect is significant especially for the Newtonian reverse shock case, as the absorption frequency ν a is larger than the cooling frequency ν c and the minimum synchrotron frequency ν m for typical parameters. For the optical to X-ray band, the flux is nearly unchanged with time during the early period, which may be a diagnostic for the low initial Lorentz factor of the ejecta in a wind environment. We also investigate the early light curves with different wind densities and compare them with those in the interstellar medium model. Ke yw ords: shock waves ‐ stars: winds, outflows ‐ gamma-rays: bursts.