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arXiv 0709.1855astro-ph
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GRB 060218:光学-UV组分的性质

GRB 060218: The nature of the optical-UV component

C. -I. Björnsson

摘要:

GRB 060218中的光学紫外分量被认为是由于光学厚回旋辐射。这个模型的关键是吸收电子的高温。热量输入来自于在半相对论性内部冲击中加速的原子核,就像普通的伽马射线暴一样。库仑碰撞将部分能量转移给电子。X射线光子的逆康普顿冷却导致电子温度约为100 keV。光学-UV发射的这种高亮度温度意味着发射面积大致等于热X射线分量的发射面积。这表明了一个模型,其中无线电,光紫外和热X射线发射是密切相关的:虽然光紫外和热X射线发射是两个独立的光谱分量,但有人认为它们都来自一个准球形的光球,连续流出,其与星周介质的相互作用引起了无线电发射。GRB 060218的性质,在同动坐标系中测量,与普通的伽马射线暴相似;即,主要区别是GRB 060218中的体洛伦兹因子的值低得多。回旋吸收意味着一个磁场与流出物中的物质能量密度大致均分。因此,磁场可能在动力学上扮演重要角色,可能是磁星作为中心引擎。

英文摘要:

The optical-UV component in GRB 060218 is assumed to be due to optically thick cyclotron emission. The key aspect of this model is the high temperature of the absorbing electrons. The heat input derives from nuclei accelerated in semi-relativistic internal shocks, like in ordinary gamma-ray bursts. Coulomb collisions transfer part of that energy to electrons. Inverse Compton cooling on the X-ray photons leads to electron temperatures around 100 keV. Such a high brightness temperature for the optical-UV emission implies an emitting area roughly equal to that of the thermal X-ray component. This suggests a model in which the radio, optical-UV and thermal X-ray emission are closely related: Although the optical-UV and thermal X-ray emission are two separate spectral components, it is argued that they both come from the photosphere of a quasi-spherical, continuous outflow, whose interaction with the circumstellar medium gives rise to the radio emission. The properties of GRB 060218, as measured in the co-moving frame, are similar to those of ordinary gamma-ray burst; i.e., the main difference is the much lower value of the bulk Lorentz factor in GRB 060218. The cyclotron absorption implies a magnetic field in rough equipartition with the matter energy density in the outflow. Hence, the magnetic field could have a dynamically important role, possibly with a magnetar as the central engine.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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