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THE DISTANCES TO OPEN CLUSTERS FROM MAIN-SEQUENCE FITTING. V. EXTENSION OF COLOR CALIBRATION AND TEST USING COOL AND METAL-RICH STARS IN NGC 6791

Title
THE DISTANCES TO OPEN CLUSTERS FROM MAIN-SEQUENCE FITTING. V. EXTENSION OF COLOR CALIBRATION AND TEST USING COOL AND METAL-RICH STARS IN NGC 6791
Authors
An, DeokkeunTerndrup, Donald M.Pinsonneault, Marc H.Lee, Jae-Woo
Ewha Authors
안덕근
SCOPUS Author ID
안덕근scopus
Issue Date
2015
Journal Title
ASTROPHYSICAL JOURNAL
ISSN
0004-637XJCR Link1538-4357JCR Link
Citation
vol. 811, no. 1
Keywords
Hertzsprung-Russell and C-M diagramsopen clusters and associations: individual (Hyades, Pleiades, Praesepe, NGC 6791)stars: distances
Publisher
IOP PUBLISHING LTD
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
We extend our effort to calibrate stellar isochrones in the Johnson-Cousins (BVIC) and the 2MASS (JHK(s)) filter systems based on observations of well-studied open clusters. Using cool main-sequence (MS) stars in Praesepe, we define empirical corrections to the Lejeune et al. color-effective temperature (T-eff) relations down to T-eff similar to 3600 K, complementing our previous work based on the Hyades and the Pleiades. We apply empirically corrected isochrones to existing optical and near-infrared photometry of cool (T-eff less than or similar to 5500 K) and metal-rich ([Fe/H] = +0.37) MS stars in NGC 6791. The current methodology relies on an assumption that color-T-eff corrections are independent of metallicity, but we find that estimates of color excess and distance from color-magnitude diagrams with different color indices converge on each other at the precisely known metallicity of the cluster. Along with a satisfactory agreement with eclipsing binary data in the cluster, we view the improved internal consistency as a validation of our calibrated isochrones at super-solar metallicities. For very cool stars (T-eff less than or similar to 4800 K), however, we find that B - V colors of our models are systematically redder than the cluster photometry by similar to 0.02 mag. We use color-T-eff transformations from the infrared flux method and alternative photometry to examine a potential color-scale error in the input cluster photometry. After excluding B - V photometry of these cool MS stars, we derive E(B - V) = 0.105 +/- 0.014, [M/H] = +0.42 +/- 0.07, (m - M)(0) = 13.04 +/- 0.08, and the age of 9.5 +/- 0.3 Gyr for NGC 6791.
DOI
10.1088/0004-637X/811/1/46
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사범대학 > 과학교육과 > Journal papers
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