NOAO > Observing Info > Approved Programs > 2008B-0449
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NOAO > Observing Info > Approved Programs > 2008B-0449 |
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PI: Sebastien Lepine, American Museum of Natural History, lepine@amnh.org
Address: Astrophysics, Central Park West at 79th street, New York, NY 10024, USA
Title: M subdwarf halo binaries and a calibration of the metallicity scale for low-mass stars.
Abstract:
We propose to obtain spectra of common proper motion doubles,
kinematically identified as local low-mass subdwarfs from the Galactic
halo (sdM+sdM). Based on their spectral subtypes and on accurate
measurements of the TiO and CaH molecular bandstrengths, we will (1)
obtain confirmation that the pairs are physical binaries, and (2) use
them to refine and calibrate the metallicity scale in low-mass, metal-
poor stars. The metal-poor, M subdwarfs show significant variations in
the absolute and relative strengths of their TiO and CaH molecular
bands, which are believed to be a function of both effective temperature
and metallicity. Spectral analysis of the sdM+sdM pairs will isolate
the effects of a variation in effective temperature, effectively tracing
iso-metallicity contours in the CaH/TiO bandstrength diagram. These
results will provide a test to the current classification scheme of M
subdwarfs. Absolute metallicity measurements of earlier-type subdwarfs,
now determined in separate programs, will be combined to the results of
this proposed program to obtain the first reliable metallicity
calibration in M subdwarfs over the full subtype range. The new
calibration will be used to determine the metallicity of over 3,500
(single star) halo M subdwarfs identified in the Sloan Digital Sky
Survey spectroscopic database, clearing the the way to a comprehensive
study of the chemical evolution of the Galaxy from the point of view of
low-mass 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 > 2008B-0449 |
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