NOAO >   Observing Info >   Approved Programs >   2008A-0095

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Proposal Information for 2008A-0095


PI: Steve B. Howell, NOAO, howell@noao.edu
Address: WIYN, 950 N. Cherry Ave., Tucson, AZ 85726, USA

CoI: Mark Giampapa, NSO
CoI: Thomas Harrison, NMSU
CoI: Suzanne Hawley, Univ. of Washington
CoI: Frank Hill, NSO
CoI: Kent Honeycutt, Indiana University
CoI: Stella Kafka, SSC
CoI: Nicole Silvestri, Univ. of Washington
CoI: Paula Szkody, Univ. of Washington
CoI: Fred Walter, SUNY
CoI: Andrew West, UC Berkeley

Title: Externally Induced or Internally Produced: What is the Source of the \it Extreme Magnetic Activity Observed in Very Low Mass Stars?

Abstract: Recent observations of the very low mass donor stars in short period interacting binaries have revealed the presence of active chromospheres. Our group has obtained initial spectra for five such systems to date and found evidence of stellar activity in all of them, including a brown dwarf mass (0.055 M-sun) donor star. The Washington group has obtained a SDSS sample of a number of close, but non-interacting white dwarf + red dwarf binaries and find H(alpha) emission related to activity. We plan to perform the first detailed phase-resolved spectroscopic study of the active chromospheres in this set of rapidly rotating (<0.3 day), low mass (<0.25 M-sun), fully convective late-type stars and brown dwarfs. Our observational goals are to study the extent, nature and short-term changes of these active chromospheres on the low mass stars of close binaries. Is the extreme activity caused by the low mass star itself or externally driven by tidal or magnetic forces? The long term goals are to complete a large enough sample (~10 systems) to provide statistically useful measurements and to use the extended time allocation to obtain long term ``coverage" spectra of each system to monitor, measure, and understand the solar-type cycles likely to be present.


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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