High resolution spectroscopy of directly imaged exoplanets with KPIC

Abstract

The Keck Planet Imager and Characterizer (KPIC) is a novel instrument that combines high-contrast imaging with high-resolution spectroscopy to enable high-dispersion coronagraphy (HDC) techniques that allow us to characterize directly imaged exoplanets at a spectral resolution of R~35,000. At this resolution, individual absorption lines in planetary atmospheres are spectrally resolved, allowing for measurements of molecular abundances to constrain chemical composition, planetary radial velocities to constrain orbital configurations, and planetary spin to constrain angular momentum evolution. I will provide an overview of the instrument, with a focus on its novel fiber injection unit (FIU) and the use of single mode fibers. I will discuss new HDC techniques we are developing that take advantage of the single-mode fibers of KPIC to both spatially and spectrally filter out the bright glare of the host stars to study the faint exoplanets. In particular, we have demonstrated the ability to forward model the high-resolution spectrum of diffracted stellar speckles, allowing us to directly fit our data without the need for cross-correlation functions. I will present some early science observations from KPIC that successfully demonstrate its technical capabilities, with the highlight being the first detection of all four HR 8799 planets at high spectral resolution. I will conclude with future avenues to push the sensitivity of HDC techniques and discuss possible synergies with other exoplanet characterization techniques such as long-baseline interferometry.