Astrophysics of Single and Binary Star Formation

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The dynamical determination of the masses of young stars and brown dwarfs will becontinued through an extensive observational program using a variety of tools andtechniques. The work is motivated by substantial uncertainties in theoretical massrelations for substellar masses, the lack of empirical calibrations (temperature,luminosity, etc.) for very low mass/young stars, and uncertainties the distribution of massratios in clusters. The goal is to obtain dynamical masses to within 10% for stars of mass1 to 0.5 that of the Sun, and to within 20% for those of even less mass. Four specificprojects will be undertaken: 1) The orbits of young visual binaries, including low masspre-main sequence stars, will be improved using Keck and Gemini Observatory laserguidestar Adaptive Optics systems and Hubble Space telescope Fine Guidance Sensorobservations. 2) The mass ratio distribution in the Hyades will be explored using theInfrared Telescope Facility and the Cryogenic Echelle Spectrograph to observespectroscopic binaries. 3) Masses of two pre-main sequence stars will be improved byobserving the rotation of circumstellar disks in the 13CO line where the ambient cloudbrightness should be lower (extended emission from the cloud was a source ofuncertainty in previous 12CO measurements). 4) The dynamical masses of brown dwarfswill be determined from observations of brown dwarf binaries, which will be used to testtheoretical mass-luminosity relations.This work will directly support the training of graduate students in contemporaryinstrumentation and collaborative investigations. Both students in the NSF supportedResearch Experiences for Undergraduates program at Stony Brook and Stony Brookundergraduates will also participate through independent research projects. Results of thework will be disseminated to the public through an ongoing monthly "Open Nights inAstronomy" program and talks to local amateur astronomy groups.