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arXiv 2208.03332astro-ph.HEastro-ph.CO
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等离子体散射中的引力透镜及其在快速射电暴中的应用

Gravitational lensing in the presence of plasma scattering with application to Fast Radio Bursts

Pawan Kumar, Paz Beniamini

摘要:

我们描述了快速射电暴(FRB)的引力透镜是如何受到透镜附近或源和观测者之间某处等离子体屏的影响。通过湍流介质的波影响引力图像放大率,透镜概率(特别是对于强放大事件)和图像之间的时间延迟。放大率被抑制,因为由等离子体散射的源的角尺寸的加宽。图像之间的时间延迟被修改为不同的色散措施(DM)的结果沿光子轨迹为不同的图像。每个图像的光变曲线也由于波散射而加宽,使得图像可以具有不同的时间轮廓。前两种效应对于恒星和亚恒星质量透镜最为严重,最后一种效应(散射增宽)对于距离源/观测者宇宙学距离的透镜和等离子体屏最为严重。这可能会限制使用FRB来测量它们的宇宙丰度。另一方面,当图像之间的时间延迟很大,这样的瞬态源的光变曲线有两个或多个分离的峰值,沿着不同的图像的波路径的不同的DM可以探测密度波动的IGM上的尺度$\lesssim 10^{-6}$ rad和探索宇宙的补丁再电离历史,在高红移使用透镜FRB。沿两个像路的不同旋转测度(RM)可以将来自源的线偏振辐射转换为部分圆偏振。

英文摘要:

We describe how gravitational lensing of fast radio bursts (FRBs) is affected by a plasma screen in the vicinity of the lens or somewhere between the source and the observer. Wave passage through a turbulent medium affects gravitational image magnification, lensing probability (particularly for strong magnification events), and the time delay between images. The magnification is suppressed because of the broadening of the angular size of the source due to scattering by the plasma. The time delay between images is modified as the result of different dispersion measure (DM) along photon trajectories for different images. Each of the image lightcurve is also broadened due to wave scattering so that the images could have distinct temporal profiles. The first two effects are most severe for stellar and sub-stellar mass lens, and the last one (scatter broadening) for lenses and plasma screens at cosmological distances from the source/observer. This could limit the use of FRBs to measure their cosmic abundance. On the other hand, when the time delay between images is large, such that the lightcurve of a transient source has two or more well separated peaks, the different DMs along the wave paths of different images can probe density fluctuations in the IGM on scales $\lesssim 10^{-6}$ rad and explore the patchy reionization history of the universe using lensed FRBs at high redshifts. Different rotation measure (RM) along two image paths can convert linearly polarized radiation from a source to partial circular polarization.

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