NOAO >   Observing Info >   Approved Programs >   2017B-0281

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Program Information for 2017B-0281


PI: Robin Jeffries, Keele University, r.d.jeffries@keele.ac.uk
Address: Astrophysics, Keele, Stoke-on-Trent, Staffordshire ST5 5BG UK

CoI: Constantine Deliyannis, Indiana U.
CoI: Richard Jackson, Keele University
CoI: Dianne Harmer, NOAO
CoI: Qinghui Sun, Indiana U.

Title: The Lithium Rotation Radius-Inflation Connection in Messier 35

Abstract: The radius of a star is a basic output from a stellar model. Yet observations of low-mass binaries and pre-main-sequence (PMS) stars show that standard evolutionary calculations underpredict their radii. This ``radius inflation'' is not yet fully explained -- it may be due to magnetic activity and rapid rotation, or it could be indicating some other deficiency in low-mass models. Lithium can provide a critically important clue: rapidly rotating G/K-dwarfs in the Pleiades have higher Li abundances at a given $T_{rm eff}$. According to some ``magnetic'' models, young, rapidly rotating stars with strong magnetic dynamos would be inflated, have cooler interiors, and undergo less PMS Li depletion than their slowly rotating siblings. These models also predict that stellar ages and masses are underestimated significantly. Accurate knowledge of stellar radii therefore directly affects estimates of the ages, radii and densities of any exoplanets that might be orbiting the stars, so {it testing these models is extremely important for exoplanetary science.} The G/K-dwarf Li/rotation/radius-inflation relations from the Pleiades represents the state-of-the-art. But these relations are scattered and defined by only a few tens of stars, and nearly all the G/K-dwarf Pleiads have already been observed. To provide a far more robust test of these relations we propose to observe over 200 G/K-dwarfs in the similarly aged (but much richer) M35, that have rotation periods from Kepler K2, thereby increasing the statistical significance of any possible relations by a large factor. We will observe Li, chromospheric activity (via H$alpha$), and $v sin i$, which, together with periods, will allow estimates of average radii for the fast rotating stars.

Program Type: Standard/NASA WIYN

Scheduled Nights:
Run 1 (2017B):  WIYN/HYDR -- 6n on Nov 20 - Nov 25 2017


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NOAO >   Observing Info >   Approved Programs >   2017B-0281

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