We study light variability of gravitationally magnified high-redshift star clusters induced by a foreground population of microlenses. This arises as the incoherent superposition of light variations from many source stars traversing the random magnification pattern on the source plane. The light curve resembles a scale-invariant, Gaussian process on time-scales of years to decades, while exhibits rapid and frequent micro-caustic crossing flares of larger amplitudes on time-scales of days to months. For a concrete example, we study a young Lyman-continuum-leaking star cluster in the Sunburst Arc at z = 2.37. We show that one magnified image happens to be intervened by a foreground galaxy, and hence should exhibit a variable flux at the 1–$2{{\ \rm per\ cent}}$ level, which is measurable in space with ∼1–$3\,$ ks exposures on the Hubble Space Telescope and more easily with the James Webb Space Telescope, or even from the ground using a ∼4-m telescope without adaptive optics. Detailed measurement of this variability can help determine the absolute macro magnification and hence the intrinsic mass and length scales of the star cluster, test synthetic stellar population models, and probe multiplicity of massive stars. Furthermore, monitoring the other lensed images of the star cluster, which are free from significant intervention by foreground microlenses, can allow us to probe planetary to stellar mass compact objects constituting as little as a few per cent of the dark matter. Given the typical surface density of intracluster stars, we expect this phenomenon to be relevant for other extragalactic star clusters lensed by galaxy clusters.

中文翻译：

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对放大的高红移星团的统计微透镜

我们研究了由前景微透镜群引起的重力放大的高红移星团的光变化。这是由于许多源星穿过源平面上的随机放大模式的光变化的不相干叠加而出现的。光变曲线在几年到几十年的时间尺度上类似于尺度不变的高斯过程，而在几天到几个月的时间尺度上表现出快速和频繁的大幅度微苛性交叉耀斑。举一个具体的例子，我们在 z = 2.37 的旭日弧中研究了一个年轻的莱曼连续介质泄漏星团。我们展示了一张放大的图像恰好被前景星系干预，因此应该表现出 1-$2{{\ \rm per\cent}}$ 水平的可变通量，这在 ∼1-$3 的空间中是可测量的\, $ ks 在哈勃太空望远镜上曝光，更容易使用詹姆斯韦伯太空望远镜，甚至使用不带自适应光学元件的 ∼4 米望远镜从地面进行曝光。对这种可变性的详细测量可以帮助确定绝对宏观放大率，从而确定星团的固有质量和长度尺度，测试合成恒星种群模型，并探测大质量恒星的多样性。此外，监测星团的其他镜头图像，这些图像不受前景微透镜的显着干预，可以让我们探测到仅占暗物质百分之几的行星到恒星质量的致密天体。鉴于星团内恒星的典型表面密度，我们预计这种现象与其他被星系团透镜化的河外星团有关。