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.

arXiv comment26 pages, 9 figures, to be published in AJ, replacement with updated minor revisions

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• Hunting for Neighboring Open Clusters with Gaia DR3: 101 New Open Clusters within 500 pc
• New Coronae and Stellar Associations Revealed by a Clustering Analysis of the Solar Neighborhood
• Searching for H${}_{\alpha }$-emitting sources in the gaps of five transitional disks. SPHERE/ZIMPOL high-contrast imaging
• The ALMA view of MP Mus (PDS 66): a protoplanetary disk with no visible gaps down to 4 au scales
• The origin of early-type runaway stars from open clusters
• The physical properties of Cluster Chains
• Young nearby open clusters and their luminosity functions
• Exploring Thousands of Nearby Hierarchical Systems with Gaia and Speckle Interferometry
• Confirmation of a ring structure in the disk around MP Mus (PDS 66) with ALMA Band 7 observations
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• Nearby Young Stars and Young Moving Groups
• Is the Young Star Association $\epsilon$Cha Double?
• Investigating 2M1155-7919B: a Nearby, Young, Low-Mass Star Actively Accreting from a Nearly Edge-on, Dusty Disk