A Kinematically Unbiased Search for Nearby Young Stars in the Northern Hemisphere Selected Using SuperWASP Rotation Periods

TL;DR

This study introduces a kinematically unbiased method to identify young, nearby low-mass stars in the northern hemisphere by combining rotation period data from SuperWASP with X-ray activity, leading to the discovery of potential members of young stellar groups.

Contribution

It presents a novel approach that uses rotation periods and X-ray activity to find young stars without relying on kinematic bias, and identifies potential members of young moving groups.

Findings

26 stars have lithium levels indicating age <=200 Myr.

11 stars are potential members of known moving groups.

7 stars may belong to the newly proposed Octans-Near group.

Abstract

We present a kinematically-unbiased search to identify young, nearby low-mass members of kinematic moving groups (MGs). Objects with both rotation periods shorter than 5 days in the SuperWASP All-Sky Survey and X-ray counterparts in the ROSAT All-Sky Survey were chosen to create a catalog of several thousand rapidly-rotating, X-ray active FGK stars. These objects are expected to be either young single stars or tidally-locked spectroscopic binaries. We obtained optical spectra for a sub-sample of 146 stars to determine their ages and kinematics, and in some cases repeat radial velocity (RV) measurements were used to identify binarity. Twenty-six stars are found to have lithium abundances consistent with an age of <=200 Myr, and show no evidence for binarity and in most cases measurements of H-alpha and v\sin i support their youthful status. Based on their youth, their radial velocities and estimates of their 3-dimensional kinematics, we find 11 objects that may be members of known MGs, 8 that do not appear associated with any young MG and a further 7 that are close to the kinematics of the recently proposed "Octans-Near" MG, and which may be the first members of this MG found in the northern hemisphere. The initial search mechanism was ~18 per cent efficient at identifying likely-single stars younger than 200 Myr, of which 80 per cent were early-K spectral types.