46 research outputs found
A Census of White Dwarfs Within 40 Parsecs of the Sun
Our aim is to compile a catalog of white dwarfs within 40 parsecs of the Sun,
in which newly discovered objects would significantly increase the completeness
of the current census. White dwarf candidates are identified from the
SUPERBLINK proper motion database (Lepine & Shara 2005), which allows us to
investigate stars down to a proper motion limit as low as 40 mas yr-1. The
selection criteria and distance estimates are based on a combination of
color-magnitude and reduced proper motion diagrams. Candidates with distances
less than 50 parsecs are selected for spectroscopic follow-up. We present our
preliminary sample of spectroscopically confirmed white dwarfs, as well as
their atmospheric parameters. These parameters are obtained using the
spectroscopic technique developed in Bergeron et al.(1992) for DA stars. DB,
DQ, and DZ stars are also analyzed spectroscopically. For featureless spectra
as well as those showing only Halpha, we perform a detailed photometric
analysis of their energy distribution.Comment: 4 pages, 3 figures, to appear in AIP Conference Proceedings for the
17th European White Dwarf Worksho
Optical BVRI Photometry of Common Proper Motion F/G/K+M Wide Separation Binaries
We present optical (BVRI) photometric measurements of a sample of 76 common
proper motion wide separation main sequence binary pairs. The pairs are
composed of a F-, G-, or K-type primary star and an M-type secondary. The
sample is selected from the revised NLTT catalog and the LSPM catalog. The
photometry is generally precise to 0.03 mag in all bands. We separate our
sample into two groups, dwarf candidates and subdwarf candidates, using the
reduced proper motion (RPM) diagram constructed with our improved photometry.
The M subdwarf candidates in general have larger colors than the M dwarf
candidates at a given color. This is consistent with an average
metallicity difference between the two groups, as predicted by the
PHOENIX/BT-Settl models. The improved photometry will be used as input into a
technique to determine the metallicities of the M-type stars.Comment: 26 pages, 8 figures, accepted for publication in A