A Coronagraph with a Sub-$\lambda /D$ IWA and a Moderate Spectral Bandwidth

Abstract

Future high-contrast imaging spectroscopy with a large segmented telescope will be able to detect atmospheric molecules of Earth-like planets around G- or K-type main-sequence stars. Increasing the number of target planets will require a coronagraph with a small inner working angle (IWA), and wide spectral bandwidth is required if we enhance a variety of detectable atmospheric molecules. To satisfy these requirements, in this paper, we present a coronagraphic system that provides an IWA less than 1${\lambda }_0/D$ over a moderate wavelength band, where ${\lambda }_0$ is the design-center wavelength and $D$ denotes the full width of the rectangular aperture included in the telescope aperture. A performance simulation shows that the proposed system approximately achieves a contrast below $10^{-10}$ at 1${\lambda }_0/D$ over the wavelengths of 650--750nm. In addition, this system has a core throughput $\ge$ 10\% at input separation angles of $\sim$ 0.7--1.4${\lambda }_0/D$; to reduce telescope time, we need prior information on the target's orbit by other observational methods to a precision higher than the width of the field of view. For some types of aberration including tilt aberration, the proposed system has a sensitivity less than ever-proposed coronagraphs that have IWAs of approximately $1{\lambda }_0/D$. In future observations of Earth-like planets, the proposed coronagraphic system may serve as a supplementary coronagraphic system dedicated to achieving an extremely small IWA.

arXiv commentAccepted for publication in the Astronomical Journal

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Cited by in corpus (3)

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• Interferometric apodization by homothety -- II. Experimental validation