Gaia-based Isochronal, Kinematic, and Spatial Analysis of the $\epsilon$ Cha Association

Abstract

The precise parallax, proper motion, and photometric measurements contained in Gaia Data Release 2 (DR2) offer the opportunity to re-examine the membership and ages of Nearby Young Moving Groups (NYMGs), i.e., loose groups of stars of age $\lesssim 100$ Myr in the solar vicinity. Here, we analyze the available DR2 data for members and candidate members of the $\epsilon$ Cha Association ($\epsilon$CA) which, at an estimated age of $\sim$3--5 Myr, has previously been identified as among the youngest NYMGs. The several dozen confirmed members of $\epsilon$CA include MP Mus and T Cha, two of the nearest stars of roughly solar mass that are known to host primordial protoplanetary disks, and the Herbig Ae/Be star HD 104237A. We have used Gaia DR2 data to ascertain the Galactic positions and kinematics and color-magnitude diagram positions of $\epsilon$CA members and candidates, so as to reassess their membership status and thereby refine estimates of the distance, age, multiplicity, and disk fraction of the group. Our analysis yields 36 \textit{bona fide} $\epsilon$CA members, as well as 20 provisional members, including 3 new members identified here as comoving companions to previously known $\epsilon$CA stars. We determine a mean distance to $\epsilon$CA of 101.0$\pm$4.6 pc and confirm that, at an age of $5_{-2}^{+3}$ Myr, $\epsilon$CA represents the youngest stellar group within $\sim$100 pc of Earth. We identify several new photometric binary candidates, bringing the overall multiplicity fraction (MF) of $\epsilon$CA to 40\%, intermediate between the MFs of young T associations and the field.

26 pages, 9 figures, to be published in AJ, replacement with updated minor revisions

References in corpus (16)

• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• Pulkovo Compilation of Radial Velocities for 35495 Hipparcos Stars in a Common System
• Search for Associations Containing Young stars (SACY): I. Sample & Searching Method
• Pre-main sequence spectroscopic binaries suitable for VLTI observations
• The VLT/NaCo Large program to probe the occurrence of exoplanets and brown dwarfs in wide orbits: I- Sample definition and characterization
• ACRONYM III: Radial Velocities for 336 Candidate Young Low-Mass Stars in the Solar Neighborhood, Including 78 Newly Confirmed Young Moving Group Members
• A CO survey in planet-forming disks: characterizing the gas content in the epoch of planet formation
• New Parallaxes and a Convergence Analysis for the TW Hya Association
• Proper motions of young stars in Chamaeleon. I. A Virtual Observatory study of spectroscopically confirmed members
• X-ray Emission from Young Stellar Objects in the εChamaeleontis Group: the Herbig Ae Star HD 104237 and Associated Low-Mass Stars
• Jet Kinematics of the Quasar 4C +21.35 from Observations with the KaVA Very Long Baseline Interferometry Array
• The Nearby, Young, Chi1 Fornacis Cluster: Membership, Age, and an Extraordinary Ensemble of Dusty Debris Disks
• Development of models for nearby young stellar moving groups: creation, revision, and finalisation of the models
• New binaries in the epsilon Cha association
• 2MASS J04435686+3723033 B: A Young Companion at the Substellar Boundary with Potential Membership in the $\beta$ Pictoris Moving Group

Cited by in corpus (3)

• The ALMA view of MP Mus (PDS 66): a protoplanetary disk with no visible gaps down to 4 au scales
• Exploring Thousands of Nearby Hierarchical Systems with Gaia and Speckle Interferometry
• Investigating 2M1155-7919B: a Nearby, Young, Low-Mass Star Actively Accreting from a Nearly Edge-on, Dusty Disk