First High-Contrast Imaging Using a Gaussian Aperture Pupil Mask

Placing a pupil mask with a Gaussian aperture into the optical train of current telescopes represents a way to attain high-contrast imaging that potentially improves contrast by orders of magnitude compared to current techniques. We present here the first observations ever using a Gaussian aperture pupil mask (GAPM) on the Penn State near-IR Imager and Spectrograph at the Mount Wilson 100'' telescope. Two nearby stars were observed, Eridani and μ Her A. A faint companion was detected around μ Her A, confirming it as a proper-motion companion. Furthermore, the observed H and K magnitudes of the companion were used to constrain its nature. No companions or faint structure were observed for Eri. We found that our observations with the GAPM achieved contrast levels similar to our coronagraphic images, without blocking light from the central star. The mask's performance also nearly reached sensitivities reported for other ground-based adaptive optics coronagraphs and deep Hubble Space Telescope images but did not reach theoretically predicted contrast levels. We outline ways that could improve the performance of the GAPM by an order of magnitude or more.