A kinematically unbiased search for nearby young stars in the Northern hemisphere selected using SuperWASP rotation periods

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 Hα 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.

LACEwING: A New Moving Group Analysis Code

“…This general behavior has been noted before, particularly in surveys that did not filter by kinematic match before following up stars for further observations (Shkolnik et al 2009(Shkolnik et al , 2012Riedel et al 2014Riedel et al , 2016bBinks et al 2015). These results have suggested that there is an unidentifiable population of young stars.…”

“…They calculated photometric distances where parallaxes were not available; all targets had γ. Binks et al (2015) studied 10 groups with individualized dispersions and set a χ 2 cutoff of 3.78, and had a maximum velocity difference of 5 km s −1 . Riedel et al (2014) studied 13 groups with individualized dispersions, and accepted a maximum χ 2 (there, called γ) value of 4.0.…”

“…The kinematic moving group identification technique in the SACY papers (e.g., Torres et al 2008, p. 757) is similar to, but simpler than the Shkolnik et al (2012), Riedel et al (2014), and Binks et al (2015) …”

“…There are also other prominent but less widely available codes, including ones used in Montes et al (2001b) and subsequent papers; Torres et al (2008, p. 757) and subsequent papers, Kraus et al (2014a), Lépine & Simon (2009) and follow-up papers (Schlieder et al 2010(Schlieder et al , 2012b(Schlieder et al , 2012c, Shkolnik et al (2012), Klutsch et al (2014), Riedel et al (2014), and Binks et al (2015). All require varying amounts of the six kinematic elements to identify objects by their kinematics, but none include all the moving groups and open clusters currently believed to exist within 100 parsecs of the Sun.…”

WEIRD: Wide-orbit Exoplanet Search with InfraRed Direct Imaging

“…A moving group is composed of stars that were formed together less than a few hundreds of Myr ago, and therefore still share similar UVW galactic velocities, enabling their identification. In recent years, a significant effort has been made to identify a large number of low-mass stars, brown dwarfs, and isolated planetary-mass objects that are members of known young moving groups (Lépine & Simon 2009;Shkolnik et al 2009Shkolnik et al , 2012Schlieder et al 2010Schlieder et al , 2012aSchlieder et al , 2012bKiss et al 2011;Rodriguez et al 2011;Liu et al 2013;Malo et al 2013Malo et al , 2014Moór et al 2013;Rodriguez et al 2013;Kraus et al 2014;Riedel et al 2014;Gagné et al 2014;Binks et al 2015;Gagné et al 2015b).…”