NOAO >   Observing Info >   Approved Programs >   2004B-0243

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Proposal Information for 2004B-0243


PI: Mark Giampapa, NSO/NOAO, giampapa@noao.edu
Address: NSO, 950 N. Cherry Ave./PO Box 26732, Tucson, AZ 85726-6732, USA

CoI: John Stauffer, IPAC/Caltech
CoI: Constantine Deliyannis, Indiana Univerity, Dept. of Astronomy
CoI: William Sherry, NOAO/NSO

Title: Chromospheric Activity at Intermediate Ages

Abstract: The calibration of the empirical relation between Ca II chromospheric strength and stellar age between 0.6 Gyr (Hyades) and 4.0 - 5 Gyr (M67 and the Sun) relies on the uncertain determination of ages for individual field stars in the solar neighborhood. We therefore propose to obtain WIYN/Hydra spectra of ~ 100 solar-type dwarf stars in the 1.8 Gyr old open cluster, NGC 752. This cluster contains a sample of solar-type dwarfs that is homogeneous in age and chemical composition. Furthermore, NGC 752 is the nearest-and hence brightest- cluster at an age ~ 2 Gyr. The results will yield an improved calibration of the age-activity relation at intermediate ages. In addition, we will determine if the chromospheric Ca II strengths for the solar-type stars in NGC 752 lie in the so-called "Vaughan-Preston Gap''- an apparent discontinuity in the Ca II H&K strength-(B-V) diagram found for field stars in the solar neighborhood. Our data will yield insight on the two proposed origins for the gap, namely, that it is a result of two different modes of dynamo action or that it is actually an artifact of a discontinuity in the local star formation rate.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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