NOAO >   Observing Info >   Approved Programs >   2016B-0132

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Program Information for 2016B-0132


PI: Donald B Lee-Brown, U. of Kansas, donald@ku.edu
Address: Physics Department, 1251 Wescoe Hall Drive, Lawrence, KS 66045-7582 USA

CoI: Bruce A Twarog, U. of Kansas
CoI: Barbara Anthony-Twarog, U. of Kansas

Title: Measuring Lithium in (gamma) Doradus Variables

Abstract: The lithium dip, observed in main sequence F-dwarfs with surface temperatures $T_{eff}$=6600$pm$200 K, is a consequence of Li transport from stellar surfaces to interior layers where the element is destroyed. By 650 Myr, stars in the dip have Li abundances $sim$2 dex below initial values, at odds with canonical stellar structure models predicting no depletion. Our extensive open cluster work indicates the extra mixing required to create the Li-dip may be connected to rotational spindown of the stellar surface. To test for a possible spindown/Li-dip connection, we propose to measure Li in $gamma$ Dor variable stars with Li-dip temperatures. $gamma$ Dor variables are an ideal test since pulsation models indicate they have convective zones insufficiently deep to deplete surface Li. Thus, assuming Li-dip formation is driven by rotational spindown, if $gamma$ Dor stars exhibit significant Li depletion, their convective zones must have extended more deeply into the interior in the past, implying lower average rotational velocities at present. If $gamma$ Dor stars show no evidence for depletion, then we expect them either to be very young and still have their initial higher rotational velocities or, if older, to have retained their initial rotational velocities.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2016B):  WIYN/HYDR -- 4n on Sep 22 - Sep 24 2016, Jan 13 - Jan 14 2017
Run 1 (2017A):  WIYN/HYDR -- 1.5n on Feb 06 - Feb 07 2017


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