Poster Open Access

A Lithium Depletion Boundary age of 40-50 Myr in NGC2232: Implications for tests of pre-main sequence stellar evolution

Alex Binks; Rob Jeffries; Richard Jackson

We identify a lithium depletion boundary (LDB) in the open cluster NGC2232, using spectroscopy obtained for high-probability
cluster members observed in the Gaia ESO Surveya. Using 2 “flavours” of evolutionary models: ones that adopt standard stellar physics (SMs) and models that incorporate some form of radius inflation either using starspots or large surface magnetic fields (MMs), we find that:
(1) LDB ages from SMs strongly agree (38±2 Myr), and those from MMs are 10–20% older, where spot-covering fraction (fsp) scales with age.
(2) The isochronal ages are 2-3 times younger using the SMs, and get closer to a 1:1 agreement for heavily-spotted models.

These results show that ages determined from CMD fits are highly sensitive to the choice of model inputs, radius inflation plays a key role for young low-mass stars, and that additional “ingredients” for models are vital to provide a full, quantitative predictive theory of pre-MS evolution.

To be presented at the Cool Stars 20.5 virtual conference.
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