Polarization light curves and position angle variation of beamed gamma-ray bursts
Polarization light curves and position angle variation of beamed gamma-ray bursts
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DOI：
10.1046/j.1365-8711.1999.03025.x
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发表时间：
1999-06
影响因子：
4.8
通讯作者：
G. Ghisellini;D. Lazzati
中科院分区：
文献类型：
--
作者：
G. Ghisellini;D. Lazzati
最近在GRB 990510的光学光变曲线中检测到的线性偏振重新引起了人们对伽马射线暴火球中如何产生偏振的兴趣。在这里，我们提出了一个模型的基础上的假设，我们看到一个准直火球，观察稍微离轴。这引入了一定程度的各向异性，并且使得即使磁场在与视线正交的平面中完全纠缠，也可以观察到线性偏振通量。我们构造了偏振通量的光变曲线，表明偏振位置角变化90 °时，它总是具有两个极大值的特征。在第一和第二最大值之间。这里假设的几何形状完全相同，这意味着总通量最初随时间按幂律衰减，但随着火球的体洛仑兹因子减小而逐渐变陡。
The recently detected linear polarization in the optical lightcurve of GRB 990510 renewed the interest on how polarization can be produced in gamma-ray burst fireballs. Here we present a model based on the assumption that we are seeing a collimated fireball, observed slightly off-axis. This introduces some degree of anisotropy, and makes it possible to observe a linearly polarized flux even if the magnetic field is completely tangled in the plane orthogonal to the line of sight. We construct the lightcurve of the polarization flux, showing that it is always characterized by two maxima, with the polarization position angle changing by 90 deg. between the first and the second maximum. The very same geometry here assumed implies that the total flux initially decays in time as a power law, but gradually steepens as the bulk Lorentz factor of the fireball decreases.