NOAO >   Observing Info >   Approved Programs >   2010B-0176

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Proposal Information for 2010B-0176


PI: Sergio B. Dieterich, Georgia State University, dieterich@chara.gsu.edu
Address: Physics Department, 29 Peachtree Center Avenue, Atlanta, GA 30303, USA

CoI: Todd J. Henry, Georgia State University

Title: Probing Stellar Physics at the Bottom of the Main Sequence: Continuing to Map the Optical Color Space for Spectral Types M6V to L5V

Abstract: We propose to continue our SOAR Optical Imager (SOI) campaign to obtain VRI photometry for a sample of 116 Very Low Mass (VLM) stars and high mass brown dwarfs. As part of a comprehensive effort involving several observatories we plan to obtain trigonometric parallaxes and to map the orbits of any newly discovered binaries in the sample. Much work has been done in the field of VLM stars and brow dwarfs during the last decade, but the fundamental question of where the exact boundary between stars and sub-stellar objects lies is still largely unanswered. This is due to the lack of reliable observational tests that discriminate between the most massive brown dwarfs and the least massive stars. Characterizing objects near this boundary is the fundamental aspect of the PI's doctoral thesis. We will use optical photometry from SOAR to place these VLM objects in color-magnitude diagrams and to refine existing bolometric corrections. Data collected thus far on 58 objects have resulted in a more precise distance-color relation for late M and early L dwarfs and an extension of the Cousins/Bessell photometric transformation equations into the very red optical regime. This work will also likely pave the path for the solid establishment of an optical photometric system for colors redder than (V-I) ~ 6. Ultimately, these observations are a crucial part of our goal of calibrating the mass-luminosity relation in the stellar/sub-stellar transition region.


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