40 research outputs found
WIYN Open Cluster Study. XIX. Main Sequence Fitting Distances to Open Clusters Using V-K Color-Magnitude Diagrams
We have combined existing optical magnitudes for stars in seven open clusters
and 54 field stars with the corresponding JHKs photometry from the Two Micron
All Sky Survey (2MASS). Combining optical with near-IR photometry broadens the
color baseline minimizing the influence of photometric errors and allows better
discrimination between cluster stars and contaminating foreground and
background populations. The open clusters in this study include NGC 2516, M35,
M34, NGC 3532, M37, M67, and NGC 188. The field stars we are using possess high
quality Hipparcos parallaxes and well-determined metal abundances allowing us
to empirically determine the dependence of (V-K) color on metal abundance in
the range -0.45<=[Fe/H]<=+0.35. Using this relation along with the parallaxes
of the field stars, we are able to construct an unevolved main sequence in the
[Mv,(V-K)o] diagram for a specific abundance. These diagrams are then used to
fit to the cluster main sequences in the [V,V-K] color-magnitude diagram in
order to estimate a distance for each open cluster. We find that the resultant
distances are within the range of distances found in the literature via the
main sequence fitting technique. It is hoped that this will spur an expansion
of the current (limited) database of star clusters with high quality (V-K)
photometry down to the unevolved main sequence.Comment: 17 pages, 7 figures, to appear in The Astronomical Journal - February
200