Mapping out the Stellar Populations of IC 2602 and IC 2391

IC 2391 and IC 2602 are important benchmarks for testing early star and planet evolution theories, both structural and dynamical, because they are the nearest open clusters with ages of similar to 50 Myr. We refine membership lists for these clusters by identifying candidate members using Gaia DR2 kinematic and distance information. We identify 451 candidate members of IC 2602 and 350 candidate members of IC 2391. If confirmed, this would increase the known populations of these clusters by 275% and 130%, respectively. We use CHIRON on the CTIO/SMARTS 1.5 m telescope via fiber mode which yields a resolution of 27,400 to acquire high-resolution spectra of 26 new candidate cluster members brighter than G = 13 magnitude, as well as an additional 12 previously known members. Measures of lithium, H alpha, stellar properties (T-eff, log(g), [Fe/H]), radial velocities, and nu sin i values from these spectra are used to confirm cluster membership. We find that 37 of 38 stars we observe are bona fide cluster members, of which four are new candidate photometric binaries and 10 are new candidate spectroscopic binaries.

Automated summary

By using Gaia DR2 data and high-resolution spectroscopy, we have refined the membership lists of the IC 2391 and IC 2602 open clusters and confirmed many new candidate members, which is important for studying the early evolution of stars and planets.