A Wolf 359 in sheep's clothing: Hunting for substellar companions in the fifth-closest system using combined high-contrast imaging and radial velocity analysis

TL;DR

This study combines high-contrast imaging and radial velocity data to search for substellar companions around Wolf 359, a nearby low-mass star, ruling out certain types of companions and assessing future direct imaging prospects.

Contribution

It integrates multiple observational techniques to constrain the presence of companions around Wolf 359 and evaluates the potential of JWST for future direct imaging.

Findings

No close stellar or brown dwarf companions detected.

Large gas-giant companions (>4 Mjup) within 10 AU are ruled out for ages under 1 Gyr.

The survey's performance and future JWST imaging capabilities are discussed.

Abstract

Wolf 359 (CN Leo, GJ 406, Gaia DR3 3864972938605115520) is a low-mass star in the fifth-closest neighboring system (2.41 pc). Because of its relative youth and proximity, Wolf 359 offers a unique opportunity to study substellar companions around M stars using infrared high-contrast imaging and radial velocity monitoring. We present the results of Ms-band (4.67 $\mu$m) vector vortex coronagraphic imaging using Keck-NIRC2 and add 12 Keck-HIRES velocities and 68 MAROON-X velocities to the radial velocity baseline. Our analysis incorporates these data alongside literature radial velocities from CARMENES, HARPS, and Keck-HIRES to rule out the existence of a close ($a < 10$ AU) stellar or brown dwarf companion and the majority of large gas-giant companions. Our survey does not refute or confirm the long-period radial velocity candidate Wolf 359 b ($P\sim2900$ d) but rules out the candidate's existence as a large gas-giant ($>4 M_{jup}$) assuming an age of younger than 1 Gyr. We discuss the performance of our high-contrast imaging survey to aid future observers using Keck-NIRC2 in conjunction with the vortex coronagraph in the Ms-band and conclude by exploring the direct imaging capabilities with JWST to observe Jupiter-mass and Neptune-mass planets around Wolf 359.