NOAO > Observing Info > Approved Programs > 2011B-0127
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NOAO > Observing Info > Approved Programs > 2011B-0127 |
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PI: John Subasavage, Cerro Tololo Interamerican Observatory, jsubasavage@ctio.noao.edu
Address: Casilla 603, La Serena, Chile
CoI: Jay Farihi, University of Leicester
CoI: Steve Margheim, Gemini Observatory - South
CoI: Boris Gaensicke, University of Warwick
Title: The Hidden Radial Velocity Companion to the Nearby Halo Star and Prototype Carbon Dwarf G77-61
Abstract:
Discovered in 1977, the nearby main-sequence star G77-61 is an extremely
metal-poor visitor from the Galactic halo and prototype of the dwarf carbon
class of stars. Over 30 years later, both its physical parameters and
evolutionary status remain poorly understood, epitomizing the shortcoming
that exists for the entire class of dwarf carbon stars; a notable component
of Galactic chemical and evolutionary history that has been overlooked. As a
low-mass star, G77-61 must be externally polluted by carbon-rich material,
presumably from a giant companion that has since evolved into a white dwarf.
Indeed, radial velocity measurements made 25 years ago seemed to indicate an
unseen companion with a period near 245 days. But this tentative result is
difficult to reconcile with theoretical expectations, as a wide orbit
inhibits significant mass transfer, and periods on 1 yr timescales are absent
among white dwarf - red dwarf binaries in the Galactic disk. We propose to
robustly determine the orbital period of the G77-61, enabling an accurate
reconstruction of its chemical history and orbital evolution, thus
constraining models for Galactic stellar and chemical evolution via the
larger class of dwarf carbon stars.
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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NOAO > Observing Info > Approved Programs > 2011B-0127 |
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