The W. M. Keck Observatory infrared vortex coronagraph and a first image of HIP79124 B

TL;DR

This paper reports the implementation of an optical vortex coronagraph at the Keck Observatory, enabling direct imaging of a close-in low-mass companion to HIP79124 and promising improved high-contrast observations of exoplanets.

Contribution

The development and on-sky demonstration of a new L'-band vortex coronagraph mode on Keck II, achieving direct imaging of a close stellar companion previously detected only by interferometry.

Findings

Resolved image of HIP79124 B at 186.5 mas separation

Enhanced imaging capabilities in L' band due to higher Strehl ratios

Potential for high-contrast small-angle exoplanet observations

Abstract

An optical vortex coronagraph has been implemented within the NIRC2 camera on the Keck II telescope and used to carry out on-sky tests and observations. The development of this new L'-band observational mode is described, and an initial demonstration of the new capability is presented: a resolved image of the low-mass companion to HIP79124, which had previously been detected by means of interferometry. With HIP79124 B at a projected separation of 186.5 mas, both the small inner working angle of the vortex coronagraph and the related imaging improvements were crucial in imaging this close companion directly. Due to higher Strehl ratios and more relaxed contrasts in L' band versus H band, this new coronagraphic capability will enable high-contrast small-angle observations of nearby young exoplanets and disks on a par with those of shorter-wavelength extreme adaptive optics coronagraphs.