Planet search with the Keck/NIRC2 vortex coronagraph in the M_s band for Vega

Abstract

Context. Gaps in circumstellar disks can signal the existence of planetary perturbers, making such systems preferred targets for direct imaging observations of exoplanets. Aims. Being one of the brightest and closest stars to the Sun, the photometric standard star Vega hosts a two-belt debris disk structure. Together with the fact that its planetary system is being viewed nearly face-on, Vega has been one of the prime targets for planet imaging efforts. Methods. Using the vector vortex coronagraph on Keck/NIRC2 in the Ms band at 4.67 μm, we report the planet detection limits from 1 au to 22 au for Vega with an on-target time of 1.8 h. Results. We reach a 3 MJupiter limit outward of 12 au, which is nearly an order of magnitude deeper than for other existing studies. Combining our observations with existing radial velocity studies, we can confidently rule out the existence of companions more than ~8 MJupiter from 22 au down to 0.1 au for Vega. Interior and exterior to ~4 au, this combined approach reaches planet detection limits down to ~2–3 MJupiter using radial velocity and direct imaging, respectively. Conclusions. By reaching multi-Jupiter mass detection limits, our results are expected to be complemented by the planet imaging of Vega in the upcoming observations using the James Webb Space Telescope to obtain a more holistic understanding of the planetary system configuration around Vega.

Vortex fiber nulling for exoplanet observations: implementation and first light

“…When used in unison with conventional coronagraphs following up on Gaia-Hipparcos accelerators, VFN can improve the separation coverage and bridge the gap between direct imaging and RV and transit surveys. 41,42 VFN also has direct application to the Habitable Worlds Observatory mission recommended by the Astro2020 Decadal Review. The stringent pointing and wavefront control requirements set by the mission's coronagraph instrument, which are on the order of tens of picometers, 43,44 far exceed the requirements for VFN.…”

“…It builds on the heritage of previous fiber nulling techniques 40 that utilize the spatial and modal filtering properties of a single-mode fiber (SMF) to simplify the optical design of classical nullers. When used in unison with conventional coronagraphs following up on Gaia-Hipparcos accelerators, VFN can improve the separation coverage and bridge the gap between direct imaging and RV and transit surveys 41 , 42 . VFN also has direct application to the Habitable Worlds Observatory mission recommended by the Astro2020 Decadal Review.…”