文章基本信息

标题：Precision Photometric and Astrometric Calibration Using Alternating Satellite Speckles
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作者：Ananya Sahoo ; Olivier Guyon ; Julien Lozi 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2020
卷号：159
期号：6
页码：3452-3460
DOI：10.3847/1538-3881/ab88cd
语种：English
出版社：American Institute of Physics
摘要：Photometric and astrometric calibration of high-contrast images is essential for the characterization of companions at small angular separation from their stellar host.The main challenge to performing accurate relative photometry and astrometry of high-contrast companions with respect to the host star is that the central starlight cannot be directly used as a reference, as it is either blocked by a coronagraphic mask or saturating the detector.Our approach is to add fiducial incoherent faint copies of the host star in the image plane and alternate the pattern of these copies between exposures.Subtracting two frames with different calibration patterns removes measurement bias due to static and slowly varying incoherent speckle halo components, while ensuring that calibration references are inserted on each frame.Each calibration pattern is achieved by high-speed modulation of a pupil-plane deformable mirror to ensure incoherence.We implemented the technique on-sky on the Subaru Coronagraphic Extreme Adaptive Optics instrument with speckles which were of the order of 103 times fainter than the central host.The achieved relative photometric and astrometric measurement precisions for 10 s exposure were respectively 5% and 20 milliarcsecond.We also demonstrate, over a 540 s measurement span, that residual photometric and astrometric errors are uncorrelated in time, indicating that residual noise averages as the inverse square root of the number of exposures in longer time-series data sets.
关键词：Astronomical instrumentation;Astrometry;Photometry;Coronagraphic imaging;Astronomical techniques;Direct imaging;Artificial satellites