Substellar Hyades Candidates from the UKIRT Hemisphere Survey

TL;DR

This study used the UKIRT Hemisphere Survey to identify and analyze potential substellar members of the Hyades cluster, discovering new candidates and refining membership probabilities through spectroscopy and kinematic analysis.

Contribution

It reports the discovery of thirteen new substellar Hyades candidates and provides a detailed kinematic and spectroscopic analysis to assess their membership, highlighting the potential for more low-mass members to be found.

Findings

Seven potential Hyades members with spectral types L5 to T4.

Five candidates show strong membership probabilities.

Some candidates could be among the lowest mass free-floating Hyades members.

Abstract

We have used data from the UKIRT Hemisphere Survey (UHS) to search for substellar members of the Hyades cluster. Our search recovered several known substellar Hyades members, and two known brown dwarfs that we suggest may be members based on a new kinematic analysis. We uncovered thirteen new substellar Hyades candidates, and obtained near-infrared follow-up spectroscopy of each with IRTF/SpeX. Six candidates with spectral types between M7 and L0 are ruled out as potential members based on their photometric distances ($\gtrsim$100 pc). The remaining seven candidates, with spectral types between L5 and T4, are all potential Hyades members, with five showing strong membership probabilities based on BANYAN $\Sigma$ and a convergent point analysis. Distances and radial velocities are still needed to confirm Hyades membership. If confirmed, these would be some of the lowest mass free-floating members of the Hyades yet known, with masses as low as $\sim$30 $M_{\rm Jup}$. An analysis of all known substellar Hyades candidates shows evidence that the full extent of the Hyades has yet to be probed for low-mass members, and more would likely be recovered with deeper photometric and astrometric investigations.