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Ages of Young Stars

Soderblom, David R. and Hillenbrand, Lynne A. and Jeffries, Rob D. and Mamajek, Eric E. and Naylor, Tim (2014) Ages of Young Stars. In: Protostars and Planets VI. University of Arizona Press , Tucson, AZ, pp. 219-241. ISBN 9780816531240.

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Determining the sequence of events in the formation of stars and planetary systems and their timescales is essential for understanding those processes, yet establishing ages is fundamentally difficult because we lack direct indicators. In this review we discuss the age challenge for young stars, specifically those less than ~ 100 m.y. old. Most age determination methods that we discuss are primarily applicable to groups of stars but can be used to estimate the age of individual objects. A reliable age scale is established above 20 m.y. from measurement of the lithium depletion boundary (LDB) in young clusters, and consistency is shown between these ages and those from the upper-main-sequence (UMS) and main-sequence (MS) tum-off - if modest core convection and rotation is included in the models of higher-mass stars. Other available methods for age estimation include the kinematics of young groups, placing stars in Hertzsprung-Russell diagrams (HRDs), pulsations and seismology, surface gravity measurement, rotation and activity, and Li abundance. We review each of these methods and present known strengths and weaknesses. Below ~20 m.y., both model-dependent and observational uncertainties grow, the situation is confused by the possibility of age spreads, and no reliable absolute ages yet exist. The lack of absolute age calibration below 20 m.y. should be born in mind when considering the lifetimes of protostellar phases and circumstellar material.

Item Type:Book Section
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Soderblom, David R.0000-0002-0322-8161
Mamajek, Eric E.0000-0003-2008-1488
Naylor, Tim0000-0002-0506-8501
Additional Information:© 2014 University of Arizona Press. E.E.M. acknowledges support from NSF grant AST-1008908. The careful reading by the referee was appreciated.
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Record Number:CaltechAUTHORS:20150128-144734095
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54198
Deposited By: Tony Diaz
Deposited On:28 Jan 2015 23:15
Last Modified:01 Nov 2019 22:52

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