Artificial incoherent speckles enable precision astrometry and photometry in high-contrast imaging

Description

State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments are constantly improving thecontrast detection limit for companions at ever-closer separations from the host star. In order to constrain theirproperties and, ultimately, compositions, it is important to precisely determine orbital parameters and contrasts withrespect to the stars they orbit. This can be difficult in the post-coronagraphic image plane, as by definition the centralstar has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in theadaptive optics system of the Subaru Coronagraphic Extreme Adaptive Optics system to generate a field of specklesfor the purposes of calibration. Speckles can be placed up to 22.5 λ/D from the star, with any position angle,brightness, and abundance required. Most importantly, we show that a fast modulation of the added speckle phase,between 0 and $\Pi$, during a long science integration renders these speckles effectively incoherent with the underlyinghalo. We quantitatively show for the first time that this incoherence, in turn, increases the robustness and stability ofthe adaptive speckles, which will improve the precision of astrometric and photometric calibration procedures. Thistechnique will be valuable for high-contrast imaging observations with imagers and integral field spectrographs alike.

Abstract

International audience

Additional details