The Tucana/Horologium, Columba, AB Doradus, and Argus Associations: New Members and Dusty Debris Disks

TL;DR

This paper identifies new members of nearby young stellar groups, analyzes their potential for adaptive optics imaging, and studies the evolution of dusty debris disks over time in relation to stellar age.

Contribution

It reports the discovery of new stellar group members, including the first A- and late-B type stars in certain groups, and examines debris disk evolution across different stellar ages.

Findings

Identification of 35 new stellar group members within 70 pc.

HR 8799 is likely a member of the 30 Myr old Columba group, refining planet mass estimates.

Debris disk occurrence decreases with stellar age, as shown by infrared excess data.

Abstract

We propose 35 star systems within ~70 pc of Earth as newly identified members of nearby young stellar kinematic groups; these identifications include the first A- and late-B type members of the AB Doradus moving group and field Argus Association. All but one of the 35 systems contain a bright solar- or earlier-type star that should make an excellent target for the next generation of adaptive optics (AO) imaging systems on large telescopes. AO imaging has revealed four massive planets in orbit around the {\lambda} Boo star HR 8799. Initially the planets were of uncertain mass due in large part to the uncertain age of the star. We find that HR 8799 is a likely member of the ~30 Myr old Columba Association implying planet masses ~6 times that of Jupiter. We consider Spitzer Space Telescope MIPS photometry of stars in the ~30 Myr old Tucana/Horologium and Columba Associations, the ~40 Myr old field Argus Association, and the ~70 Myr old AB Doradus moving group. The percentage of stars in these young stellar groups that display excess emission above the stellar photosphere at 24 and 70 \mu m wavelengths - indicative of the presence of a dusty debris disk - is compared with corresponding percentages for members of 11 open clusters and stellar associations with ages between 8 and 750 Myr, thus elucidating the decay of debris disks with time.