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The Problem Of Hipparcos Distances To Open Clusters. I. Constraints From Multicolor Main-Sequence Fitting, Marc H. Pinsonneault, John Stauffer, David Soderblom, Jeremy R. King, Robert B. Hanson
The Problem Of Hipparcos Distances To Open Clusters. I. Constraints From Multicolor Main-Sequence Fitting, Marc H. Pinsonneault, John Stauffer, David Soderblom, Jeremy R. King, Robert B. Hanson
Publications
Parallax data from the Hipparcos mission allow the direct distance to open clusters to be compared with the distance inferred from main-sequence (MS) Ðtting. There are surprising differences between the two distance measurements, indicating either the need for changes in the cluster compositions or reddening, underlying problems with the technique of MS Ðtting, or systematic errors in the Hipparcos parallaxes at the 1 mas level. We examine the di†erent possibilities, focusing on MS fitting in both metallicity-sensitive B[V and metallicity-insensitive V [I for five well-studied systems (the Hyades, Pleiades, a Per, Praesepe, and Coma Ber). The Hipparcos distances to the …
Lithium In The Young Cluster Ngc 2264, Jeremy R. King
Lithium In The Young Cluster Ngc 2264, Jeremy R. King
Publications
We use moderate-resolution, moderate signal-to-noise ratio spectroscopy to derive Li abundances for six F and G stars in the young (few Myr) cluster NGC 2264. These are combined with consistently determined abundances of five NGC 2264 G and K stars having published Li data. The mean non-LTE abundance, calculated with photometric temperatures, is log N(Li) = 3.27 ± 0.05. This is essentially identical to the meteoritic value, providing no evidence of Galactic Li enrichment over the past 4.6 Gyr—at least to the extent that the meteoritic value represents a typical "cosmic" value at that time. The scatter of 0.16 dex …