NOAO >   Observing Info >   Approved Programs >   2006A-0142

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Proposal Information for 2006A-0142


PI: Beth Biller, Steward Observatory, bbiller@as.arizona.edu
Address: University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85705, USA

CoI: Laird Close, Steward Observatory, University of Arizona
CoI: James Liebert, Steward Observatory, University of Arizona

Title: Direct Distance Determination for an Extrasolar Planet Candidate and Young Brown Dwarfs

Abstract: The distribution of masses, luminosities, and binarities of young substellar objects and planetary mass objects is not well known. Directly measuring distances to young substellar objects using trigonometric parallax will lead to the first accurate determination of young substellar object luminosities. Such luminosities are invaluable for constraining models of young substellar objects. We propose to measure parallaxes for 2 young substellar objects which are tentative TW Hya cluster members. One of our target objects, 2MASS 1207, is thought to be an M8 brown dwarf with a L5-L9 planetary mass companion (Chauvin et al. 2004). However, the photometry and lithium absorption features of this object are consistent with an ensemble of objects with masses of 20-80 M_Jup for the primary and masses of 5-20 M_Jup for the secondary, with ages <200 Myr and at distances of 20-70 pc. Additionally, Reid et al. 2002 found that LP 944-20, a field M9.5 brown dwarf with a \bf measured distance of 5 pc (from trigonometric parallaxes by Tinney 1996) and luminosity consistent with ages of 1-10 Gyr, had very strong lithium absorption (0.5 AEW, nearly identical to that of 2MASS 1207). \bf If 2MASS1207 was a clone of LP 944-20, it would lie 15.5 pc from the Earth and have an easily measured parallax of 65 mas. A direct measurement of the trigonometric parallax for this system would settle once and for all whether the companion to 2MASS 1207 is a planet or a brown dwarf.


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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