The Distances to Open Clusters from Main-Sequence Fitting. III. Improved Accuracy with Empirically Calibrated Isochrones

We continue our series of papers on open cluster distances with a critical assessment of the accuracy of main-sequence fitting using isochrones that employ empirical corrections to the color-temperature relations. We use four nearby open clusters with multicolor photometry and accurate metallicities...

Full description

Saved in:
Bibliographic Details
Published in:The Astrophysical journal 2007-01, Vol.655 (1), p.233-260
Main Authors: An, Deokkeun, Terndrup, Donald M, Pinsonneault, Marc H, Paulson, Diane B, Hanson, Robert B, Stauffer, John R
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We continue our series of papers on open cluster distances with a critical assessment of the accuracy of main-sequence fitting using isochrones that employ empirical corrections to the color-temperature relations. We use four nearby open clusters with multicolor photometry and accurate metallicities and present a new metallicity for Praesepe ([Fe/H] = +0.11 c 0.03) from high-resolution spectra. The internal precision of distance estimates is about a factor of 5 better than the case without the color calibrations. After taking into account all major systematic errors, we obtain distances accurate to about 2%-3% when there exists a good metallicity estimate. Metallicities accurate to better than 0.1 dex may be obtained from BVI sub(C)K sub(s) photometry alone. We also derive a helium abundance for the Pleiades of Y= 0.279 c 0.015, which is equal within the errors to the Sun's initial helium abundance and that of the Hyades. Our best estimates of distances are (m - M) sub(0) = 6.33 c 0.04, 8.03 c 0.04, and 9.61 c 0.03 to Praesepe, NGC 2516, and M67, respectively. Our Pleiades distance at the spectroscopic metallicity, (m - M) sub(0) = 5.66 c 0.01 (internal) c 0.05(systematic), is in excellent agreement with several geometric distance measurements. We have made calibrated isochrones for -0.3 , [Fe/H] , +0.2 available online.
ISSN:0004-637X
1538-4357
DOI:10.1086/509653