The Coherent Differential Imaging on Speckle Area Nulling (CDI-SAN) Method for High-contrast Imaging under Speckle Variation

• Published in: The Astrophysical journal Vol. 930; no. 2; pp. 163 - 172
• Main Author: Nishikawa, Jun
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-05-2022; IOP Publishing
• Subjects: Astrophysics; Coronagraphic imaging; Deformable mirrors; Direct imaging; Exoplanet detection methods; Exoplanets; Extrasolar planets; Formability; Image acquisition; Planet detection; Space telescopes; Telescopes
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac5f44

Differential imaging is a postprocessing method to obtain high contrast, often used for exoplanet searches. The coherent differential imaging on speckle area nulling (CDI-SAN) method was developed to detect a faint exoplanet lying beneath residual speckles of a host star. It utilizes image acquisitions faster than the stellar speckle variation synchronized with five shapes of a deformable mirror repeatedly. By using only the integrated values of each of the five images and square differences for a long interval of observations, the light of the exoplanet could be separated from the stellar light. The achievable contrast would reach almost the photon-noise limit of the residual speckle intensities under appropriate conditions. CDI-SAN can be applied to both ground-based and space telescopes.