NOAO >   Observing Info >   Approved Programs >   2009A-0084

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Proposal Information for 2009A-0084


PI: Edo Berger, Harvard University, eberger@cfa.harvard.edu
Address: Astronomy Department, 60 Garden St., MS-19, Cambridge, MA 02138, USA

CoI: Mark Giampapa, NOAO
CoI: William Sherry, NOAO

Title: The Lifetime of Magnetic Fields in Fully Convective Brown Dwarfs

Abstract: Until recently theoretical expectation was that magnetic activity would disappear in fully convective ultracool dwarfs (very low mass stars and brown dwarfs). We now know that magnetic activity in fact exists, but the origin, configuration, and lifetime of the field and dynamo remain largely unconstrained. Numerical simulations cannot presently accommodate the relevant conditions in the lowest mass objects, and progress mainly relies on observational clues. Recently, we uncovered the first examples of periodic and sinusoidal H(alpha) emission from two ultracool dwarfs (with a period of 2 hours). The H(alpha) emission is due to a large-scale magnetic hot spot that rigidly rotates with the stars. Here we propose observations separated by 1 and 2 years from the original discovery in order to assess the stability timescale of the magnetic field, a crucial constraint on the nature of the dynamo mechanism.


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NOAO >   Observing Info >   Approved Programs >   2009A-0084

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