Young Stars Near Earth: The Octans-Near Association and Castor Moving Group

TL;DR

This paper identifies a nearby group of young stars called Octans-Near with similar space motions to the distant Octans Association, discusses their ages, and explores their relation to other stellar groups like Castor.

Contribution

It presents a new list of 14 nearby stars with similar UVW velocities to the distant Octans Association, suggesting a potential nearby young stellar group.

Findings

Octans-Near stars are 30-100 Myr old and within 100 pc.

Six additional stars likely younger than 200 Myr with similar UVW.

The Castor group, if real, is older than 200 Myr and distinguishable from Octans-Near.

Abstract

All cataloged stellar moving groups and associations with ages <100 Myr and within 100 pc of Earth have Galactic space motions (UVW) situated in a "good box" with dimensions ~20 km/s on a side. Torres et al. defined the Octans Association as a group of 15 stars with age "20 Myr?" and located ~140 pc from Earth, but with average V space velocity -3.6 km/s that is well outside of the good box. We present a list of 14 Hipparcos star systems within 100 pc of Earth that we call "Octans-Near"; these systems have UVW similar to those of the much more distant Octans Association. The Octans-Near stars have apparent ages between about 30 and 100 Myr and their relationship to the Octans Association stars is unclear. Six additional star systems have UVW similar to those of Octans-Near stars and likely ages <200 Myr. These six systems include the late-type binary star EQ Peg -- 6.2 pc from Earth with likely age <100 Myr and thus likely to be the nearest known pre-main sequence star system. The UVW of stars in a previously proposed ~200 Myr old Castor moving group are not too dissimilar from the UVW of Octans-Near stars. However, stars in the Castor group -- if it exists at all -- are mostly substantially older than 200 Myr and thus generally can readily be distinguished from the much younger Octans-Near stars.