We present evidence that spots imaged using astronomical CCDs do not exactly scale with flux: bright spots tend to be broader than faint ones, using the same illumination pattern. We measure that the linear size of spots or stars, of typical size 3 to 4 pixels FWHM, increase linearly with their flux by up to $2\%$ over the full CCD dynamic range. This brighter-fatter effect affects both deep-depleted and thinned CCD sensors. We propose that this effect is a direct consequence of the distortions of the drift electric field sourced by charges accumulated within the CCD during the exposure and experienced by forthcoming light-induced charges in the same exposure. The pixel boundaries then become slightly dynamical: overfilled pixels become increasingly smaller than their neighbors, so that bright star sizes, measured in number of pixels, appear larger than those of faint stars. This interpretation of the brighter-fatter effect implies that pixels in flat-fields should exhibit statistical correlations, sourced by Poisson fluctuations, that we indeed directly detect. We propose to use the measured correlations in flat-fields to derive how pixel boundaries shift under the influence of a given charge pattern, which allows us to quantitatively predict how star shapes evolve with flux. This physical model of the brighter-fatter effect also explains the commonly observed phenomenon that the spatial variance of CCD flat-fields increases less rapidly than their average.
The shape of the Photon Transfer Curve of CCD sensors
CCD的光子传输曲线（PTC）描述了均匀图像的方差作为其平均值的函数。现在已经很好地确定，方差与平均值不成比例，正如泊松统计所表明的那样，而是在高通量下不成比例。这种与较亮-较胖效应相关的“方差赤字”提供了附近像素之间的相关性，这些相关性随通量增加而增加，并随距离衰减。我们提出了一个解析表达式的PTC形状，并与强度的相关性的依赖关系，并涉及到一些更基本的量与传感器的静电，这是常用的校正科学图像的亮度，脂肪的效果。我们从一个大的一组与CCD E2 V 250获得的平场图像的静电约束，并最终质疑普遍承认的假设，CCD像素的边界移位量成正比的源电荷。我们的结果表明，从泊松定律的平场统计的偏离是完全兼容的漂移过程中的传感器中的电荷重新分布。
The nonlinear photon transfer curve of CCDs and its effects on photometry
光子传输曲线（PTC，方差与信号电平）是表征CCD性能的常用且有效的工具。在光子散粒噪声占主导地位的范围内，它在理论上是线性的，并且它的斜率被用来导出CCD的增益。然而，最近对不同CCD的研究表明，在高信号水平下，方差逐渐下降，而信号与曝光时间的线性关系仍然很好，不受影响。另一方面，亮星表现出较胖的点扩散函数（PSF）。非线性PTC和亮胖效应都被认为是像素之间电荷扩散的结果，这种相互作用随着信号电平的增加而增加。在这项工作中，我们研究了非线性PTC的基础上的图像与STA 1600 FT CCD相机，其PTC开始成为非线性约1/3满阱。为了解释这一现象，我们提出了一个模型来表征电荷共享PSF。这种信号依赖的PSF可以从平场框架中导出，并允许我们量化测光和测量的恒星形状的影响。这种效应对于需要精确光度和形状参数的项目至关重要。
The Nancy Grace Roman Space Telescope Wide Field Instrument: Characterization of the Brighter-Fatter Effect in a Roman H4RG-10 Detector using the Talbot Effect
University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；Center for Research and Exploration in Space Science and Technology（空间科学与技术研究探索中心）；Space Telescope Science Institute（太空望远镜科学研究所）
Charge migration characterization in the METIS H2RG detectors
Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；European Southern Observatory（欧洲南方天文台）；Institute of Astronomy, KU Leuven（荷语鲁汶大学天文学研究所）；UK Astronomy Technology Centre（英国天文学技术中心）
