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Full-Text Articles in Physical Sciences and Mathematics
Lithium In The Upper Centaurus Lupus And Lower Centaurus Crux Subgroups Of Scorpius-Centaurus, Eric J. Bubar, Marc Schaeuble, Jeremy R. King, Eric E. Mamajek, John R. Stauffer
Lithium In The Upper Centaurus Lupus And Lower Centaurus Crux Subgroups Of Scorpius-Centaurus, Eric J. Bubar, Marc Schaeuble, Jeremy R. King, Eric E. Mamajek, John R. Stauffer
Publications
We utilize spectroscopically derived model atmosphere parameters and the Li i λ6104 subordinate line and the λ6708 doublet to derive lithium abundances for 12 members of the Upper Centaurus Lupus and Lower Centaurus Crux subgroups of the Scorpius–Centaurus OB Association. The results indicate any intrinsic Li scatter in our 0.9–1.4 M stars is limited to ∼0.15 dex, consistent with the lack of dispersion in 1.0 M stars in the 100 Myr Pleiades and 30–50 Myr IC 2391 and 2602 clusters. Both ab initio uncertainty estimates and the derived abundances themselves indicate that the λ6104 line yields abundances with equivalent or …
Spectroscopic Abundances And Membership In The Wolf 630 Moving Group, Eric J. Bubar, Jeremy R. King
Spectroscopic Abundances And Membership In The Wolf 630 Moving Group, Eric J. Bubar, Jeremy R. King
Publications
The concept of kinematic assemblages evolving from dispersed stellar clusters has remained contentious since Eggen’s initial formulation of moving groups in the 1960s. With high-quality parallaxes from the Hipparcos space astrometry mission, distance measurements for thousands of nearby, seemingly isolated stars are currently available. With these distances, a high-resolution spectroscopic abundance analysis can be brought to bear on the alleged members of these moving groups. If a structure is a relic of an open cluster, the members can be expected to be monolithic in age and abundance in as much as homogeneity is observed in young open clusters. In this …
Fe I And Fe Ii Abundances Of Solar-Type Dwarfs In The Pleiades Open Cluster, Simon C. Schuler, Adele L. Plunkett, Jeremy R. King, Marc H. Pinsonneault
Fe I And Fe Ii Abundances Of Solar-Type Dwarfs In The Pleiades Open Cluster, Simon C. Schuler, Adele L. Plunkett, Jeremy R. King, Marc H. Pinsonneault
Publications
We have derived Fe abundances of 16 solar-type Pleiades dwarfs by means of an equivalent width analysis of Fe I and Fe II lines in high-resolution spectra obtained with the Hobby - Eberly Telescope and High Resolution Spectrograph. Abundances derived from Fe II lines are larger than those derived from Fe I lines (herein referred to as over-ionization) for stars with Teff < 5400 K, and the dis-crepancy (∆Fe = [Fe II/H] - [Fe I/H]) increases dramatically with decreasing Teff, reaching over 0.8 dex for the coolest stars of our sample. The Pleiades joins the open clusters M34, the Hyades, IC2602, and IC2391, and the Ursa Major moving group, demonstrating ostensible over-ionization trends. The Pleiades ∆Fe abun-dances are correlated with Ca II infrared triplet and Hα chromospheric emission indicators and relative differences therein. Oxygen abundances of our Pleiades sample derived from the high-excitation O I triplet have been previously shown to increase with decreasing Teff, and a comparison with the ∆Fe abundances sug-gests that the over-excitation (larger abundances derived from high excitation lines relative to low excitation lines) and over-ionization effects that have been observed in cool open cluster and disk field main sequence (MS) dwarfs share a common origin. Curiously, a correlation between the Pleiades O I abundances and chromospheric emission indicators does not exist. Star-to-star Fe I abun-dances have low internal scatter (< 0.11 dex), but the abundances of stars with Teff< 5400 K are systematically higher compared to the warmer stars. The cool star [Fe I/H] abundances cannot be connected directly to over-excitation effects, but similarities with the ∆Fe and O I triplet trends suggest the abundances are dubious. Using the [Fe I/H] abundances of five stars with Teff > 5400 K, we derive a mean Pleiades cluster metallicity of [Fe/H] = +0.01 ± 0.02.
Possible Identification Of A Metal-Rich Old Moving Group: High-Resolution Spectroscopy Of Candidate Members, Abigail R. Daane, Jeremy R. King, Simon C. Schuler
Possible Identification Of A Metal-Rich Old Moving Group: High-Resolution Spectroscopy Of Candidate Members, Abigail R. Daane, Jeremy R. King, Simon C. Schuler
Publications
Using new high-resolution spectroscopic observations from both the McDonald Observatory 2.7 m and Kitt Peak National Observatory 4 m telescopes, we observed four candidate members of the Ursa Major moving group previously suggested to instead belong to a significantly older kinematic assemblage. The Fe abundances we measure strongly suggest that these stars are not UMa members but form a more metal-rich group of stars (+0.10 ≤ [Fe/H] ≤ +0.18) with an age near 3 Gyr. Our [Ca/H] determinations corroborate this result. The apparent similarities in metallicity and previously discovered UVW space motions lend credence to prior suggestions that these stars …
Oxygen In Open Cluster Dwarfs: Pleiades And M34, Simon C. Schuler, Jeremy R. King, L M. Hobbs, Marc H. Pinsonneault
Oxygen In Open Cluster Dwarfs: Pleiades And M34, Simon C. Schuler, Jeremy R. King, L M. Hobbs, Marc H. Pinsonneault
Publications
We analyze the high-excitation O I lambda7774 triplet in high-resolution, moderate signal-to-noise ratio spectra of 15 Pleiades and eight M34 open cluster dwarfs over the effective temperature range of 5048-6172 K. Relative O abundances have been derived using model atmospheres interpolated from four different sets of ATLAS9 grids. In contrast to existing non-LTE (NLTE) predictions, a dramatic increase in the O I triplet abundance with decreasing temperature is seen for both clusters, regardless of the atmospheric model. S I abundances of three Pleiades stars derived from the high-excitation lambda6053 feature mimic the O I abundance behavior. O abundances have also …