Infrared study of the eta Chamaeleontis cluster and the longevity of circumstellar discs

Abstract

We have analyzed JHKL observations of the stellar population of the ~9 Myr-old eta Chamaeleontis cluster. Using infrared (IR) colour-colour and colour-excess diagrams, we find the fraction of stellar systems with near-IR excess emission is 0.60 pm 0.13 (2_sigma). This results implies considerably longer disc lifetimes than found in some recent studies of other young stellar clusters. For the classical T Tauri (CTT) and weak-lined T Tauri (WTT) star population, we also find a strong correlation between the IR excess and H_alpha emission. The IR excesses of these stars indicate a wide range of star-disc activity; from a CTT star showing high levels of accretion, to CTT - WTT transition objects with evidence for some on-going accretion, and WTT stars with weak or absent IR excesses. Of the 15 known cluster members, 4 stars with IR excesses delta(K-L) > 0.4 mag are likely experiencing on-going accretion owing to strong or variable optical emission. The resulting accretion fraction (0.27 pm 0.13; 2_sigma) shows that the accretion phase, in addition to the discs themselves, can endure for at least ~10 Myr.

arXiv comment7 pages, 4 figures, accepted for MNRAS

References in corpus (11)

• Disk Frequencies and Lifetimes in Young Clusters
• Post-T Tauri Stars in the Nearest OB Association
• Infrared L Band Observations of the Trapezium Cluster: A Census of Circumstellar Disks and Candidate Protostars
• A Near-Infrared L Band Survey of the Young Embedded Cluster NGC 2024
• Deep 10 and 18 micron Imaging of the HR 4796A Circumstellar Disk: Transient Dust Particles & Tentative Evidence for a Brightness Asymmetry
• The Eta Chamaeleontis Cluster: Origin in the Sco-Cen OB Association
• Line profile variations in $\gamma$ Doradus
• Disk-locking and the presence of slow rotators among solar-type stars in young star clusters
• ECHA J0843.3-7905: Discovery of an 'old' classical T Tauri star in the eta Chamaeleontis cluster
• A Three Micron Survey of the Chamaeleon I Dark Cloud
• Angular Momentum Evolution of Stars in the Orion Nebula Cluster

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