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Techniques for High-contrast Imaging in Multi-star Systems. II. Multi-star Wavefront Control

2017; IOP Publishing; Volume: 849; Issue: 2 Linguagem: Inglês

10.3847/1538-4357/aa8e02

1538-4357

Dan Sirbu, Sandrine Thomas, Ruslan Belikov, Eduardo Bendek,

Astronomy and Astrophysical Research

Abstract Direct imaging of exoplanets represents a challenge for astronomical instrumentation due to the high-contrast ratio and small angular separation between the host star and the faint planet. Multi-star systems pose additional challenges for coronagraphic instruments due to the diffraction and aberration leakage caused by companion stars. Consequently, many scientifically valuable multi-star systems are excluded from direct imaging target lists for exoplanet surveys and characterization missions. Multi-star Wavefront Control (MSWC) is a technique that uses a coronagraphic instrument’s deformable mirror (DM) to create high-contrast regions in the focal plane in the presence of multiple stars. MSWC uses “non-redundant” modes on the DM to independently control speckles from each star in the dark zone. Our previous paper also introduced the Super-Nyquist wavefront control technique, which uses a diffraction grating to generate high-contrast regions beyond the Nyquist limit (nominal region correctable by the DM). These two techniques can be combined as MSWC-s to generate high-contrast regions for multi-star systems at wide (Super-Nyquist) angular separations, while MSWC-0 refers to close (Sub-Nyquist) angular separations. As a case study, a high-contrast wavefront control simulation that applies these techniques shows that the habitable region of the Alpha Centauri system can be imaged with a small aperture at <?CDATA $8\times {10}^{-9}$?> mean raw contrast in 10% broadband light in one-sided dark holes from 1.6–5.5 λ / D . Another case study using a larger 2.4 m aperture telescope such as the Wide-Field Infrared Survey Telescope uses these techniques to image the habitable zone of Alpha Centauri at <?CDATA $3.2\times {10}^{-9}$?> mean raw contrast in monochromatic light.