通过用于K2、TESS及更高级别的光束整形漫射器，从地面实现极高精度photometry
Extreme precision photometry from the ground with beam-shaping diffusers for K2, TESS and beyond
摘要：
凌日系外行星调查卫星（TESS，2018年初发射）预计将在最近和最亮的恒星周围发现大量新的凌日系外行星候选者。从地面进行及时的高精度后续观测对于确认和进一步描述TESS将发现的行星候选者至关重要。然而，从地面实现极端的测光精度是具有挑战性的，因为地基望远镜受到许多有害的大气影响。光束整形漫射器作为一种低成本技术正在兴起，以实现迄今为止无法实现的地面差分测光精度。这些扩散器将恒星的焦平面图像塑造成一个广泛而稳定的礼帽形状，最大限度地减少由于不均匀的像素响应，大气视宁度效应，不完善的指导，以及望远镜引起的散焦可变像差造成的光度误差。在本文中，我们扩展了我们以前的工作（Stefansson et al. 2017; Stefansson et al. 2018 [已提交]），进一步详细讨论了在望远镜上使用漫射器时的关键准则。此外，我们提出了我们的开源Python包iDiffuse，它可以计算望远镜系统中漫射器的预期PSF大小，以及给定星等的主星的预期天空漫射器辅助光度精度。我们使用iDiffuse表明，大多数（$\sim$ 80\%）的行星主机，TESS将发现将闪烁有限的过境观测从地面。虽然iDiffuse的开发主要是为了计划使用Apache Point天文台ARC 3.5米望远镜上的ARCTIC成像仪上的漫射器进行具有挑战性的凌日观测，但iDiffuse是模块化的，可以很容易地扩展到计算其他望远镜上预期的漫射器辅助光度精度。
英文摘要：
The Transiting Exoplanet Survey Satellite (TESS, launched early 2018) is expected to find a multitude of new transiting planet candidates around the nearest and brightest stars. Timely high-precision follow-up observations from the ground are essential in confirming and further characterizing the planet candidates that TESS will find. However, achieving extreme photometric precisions from the ground is challenging, as ground-based telescopes are subject to numerous deleterious atmospheric effects. Beam-shaping diffusers are emerging as a low-cost technology to achieve hitherto unachievable differential photometric precisions from the ground. These diffusers mold the focal plane image of a star into a broad and stable top-hat shape, minimizing photometric errors due to non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and telescope-induced variable aberrations seen in defocusing. In this paper, we expand on our previous work (Stefansson et al. 2017; Stefansson et al. 2018 [submitted]), providing a further detailed discussion of key guidelines when sizing a diffuser for use on a telescope. Furthermore, we present our open source Python package iDiffuse which can calculate the expected PSF size of a diffuser in a telescope system, along with its expected on-sky diffuser-assisted photometric precision for a host star of a given magnitude. We use iDiffuse to show that most ($\sim$80\%) of the planet hosts that TESS will find will be scintillation limited in transit observations from the ground. Although iDiffuse has primarily been developed to plan challenging transit observations using the diffuser on the ARCTIC imager on the ARC 3.5m Telescope at Apache Point observatory, iDiffuse is modular and can be easily extended to calculate the expected diffuser-assisted photometric precisions on other telescopes.
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