The age rank of the nearest pre-main-sequence groups

Authors

  • Warrick A. Lawson,

    Corresponding author
    1. School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia
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  • A-Ran Lyo,

    Corresponding author
    1. Korea Astronomy and Space Science Institute, 61-1, Hwaam-dong, Yuseong-gu, Daejeon 305-348, Korea
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  • M. S. Bessell

    Corresponding author
    1. Research School of Astronomy and Astrophysics, Institute of Advanced Studies, The Australian National University, Cotter Road, Weston Creek ACT 2611, Australia
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E-mail: w.lawson@adfa.edu.au (WAL); arl@kasi.re.kr (A-RL); bessell@mso.anu.edu.au (MSB)

ABSTRACT

We address the age rank of the nearest pre-main-sequence (PMS) associations, using low-resolution spectrophotometry to measure gravity-sensitive indices in these stars. We compare spectral index-colour sequences for the PMS populations and rank them according to the strength of their gravity-sensitive features. The age rank using the gravity method is in general agreement with the ranking of these groups suggested by colour–magnitude (CM) diagram placement. Several of the groups have a kinematic origin in the Oph-Sco-Cen OB association. For three of them, their age rank is also in agreement with epochs resulting from a formation scenario for the OB association.

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