THE REALITY OF THE WOLF 630 MOVING GROUP

The concept of relic kinematic assemblages from dispersed stellar clusters has remained contentious since Eggen\u27s initial formulation of moving groups in the 1960\u27s. However, the availability of high quality parallaxes from the Hipparcos space astrometry mission has resulted in distance measurements for thousands of nearby, seemingly isolated stars. With these newly determined distances, a high resolution spectroscopic abundance analysis can be brought to bear on many of the alleged members of these relic associations. If a structure is a relic of an open cluster, the members can be expected to be monolithic in age and abundance inasmuch as homogeneity is observed in young open clusters. In this dissertation I have examined 34 members of the Wolf 630 moving group using high resolution stellar spectroscopy. The stars of the sample have been analyzed through a process known as chemical tagging to determine abundance homogeneity and confirm the existence of a homogeneous subsample of 20 stars. Fitting the homogeneous subsample with Yale-Yonsei isochrones, yields a single evolutionary sequence of ∼ 2.7 ± 0.5 Gyr. Additionally basic N-Body simulations, using the NEMO Stellar Dynamics toolkit, have been used to examine the kinematic evolution of typical star clusters in a model galactic disk potential that has been studded with Giant Molecular clouds. The results of these simulations suggests a high degree of kinematic coherence following spatial dissolution, validating that open clusters can maintain a common kinematic identity following their loss of spatial concordance. It is, therefore, concluded that moving groups can plausibly represent the relics of dissolved open clusters and that a 20 star subsample of the Wolf 630 moving group sample of 34 stars could represent such a dispersed cluster with an [Fe/H]=-0.01 ± 0.02 and an age of 2.7 ± 0.5 Gyr

Alien Registration- Bubar, Lloyd A. (Houlton, Aroostook County)

https://digitalmaine.com/alien_docs/35961/thumbnail.jp

KECK HIRES SPECTROSCOPY OF CANDIDATE POST T TAURI STARS

This work utilizes an age-oriented method to identify isolated post T Tauri stars in a 13-star sample of high resolution spectroscopy from the 10-m Keck telescope. This analysis utilizes qualitative age information derived from lithium abundances, chromospheric emission indices and UVW kinematic motions in analyzing positions in the the H-R diagram. Once qualitatively assigned a ``young\u27\u27 age, pre-main sequence isochrones are utilized to determine stellar mass and age estimates. Through this method, 5 of the 13 stars have been confirmed as being in the post T Tauri class. We also examine irregular photometric variability of PTTs and compare the homology of observed SED\u27s with model atmospheres which reveals a possible near-IR excess. We conclude that our age oriented analysis is a robust means to select samples of nearby, young, isolated post T Tauri stars that otherwise masquerade as normal field stars

Alien Registration- Bubar, Isaac B. (Limestone, Aroostook County)

https://digitalmaine.com/alien_docs/35082/thumbnail.jp

Letter from the Christian Civic League of Maine

Letter from Rev. Benjamin C. Bubar, Jr. of the Christian Civic League of Maine expressing homophobic views and denouncing the University\u27s position regarding the Wilde-Stein Club and gay symposium

Lithium in the Upper Centaurus Lupus and Lower Centaurus Crux Subgroups of Scorpius-Centaurus

We utilize spectroscopically derived model atmosphere parameters and the \ion{Li}{1} $\lambda6104$ subordinate line and the $\lambda6708$ doublet to derive lithium abundances for 12 members of the Upper-Centaurus Lupus (UCL) and Lower-Centaurus Crux (LCC) subgroups of the Scorpius Centaurus OB Association. The results indicate any intrinsic Li scatter in our 0.9-1.4 $M_{\odot}$ stars is limited to ${\sim}0.15$ dex, consistent with the lack of dispersion in ${\ge}1.0$ $M_{\odot}$ 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 $\lambda$6104 line yields abundances with equivalent or less scatter than is found from the $\lambda$6708 doublet as a result of lower uncertainties for the subordinate feature, a result of low sensitivity to broadening in the subordinate feature. Because NLTE corrections are less susceptible to changes in surface gravity and/or metallicity for the 6104 {\AA} line, the subordinate Li feature is preferred for deriving lithium abundances in young Li-rich stellar association stars with $T_{\rm eff}{\ge}5200$ K.Comment: Accepted for publication in Astronomical Journal (abstract shortened for astro-ph submission

Spectroscopic Abundances and Membership in the Wolf 630 Moving Group

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 work, we have examined 34 putative members of the proposed Wolf 630 moving group using high-resolution stellar spectroscopy. The stars of the sample have been chemically tagged to determine abundance homogeneity and confirm the existence of a homogeneous subsample of 19 stars. Fitting the homogeneous subsample with Yale–Yonsei isochrones yields a single evolutionary sequence of ∼2.7 ± 0.5 Gyr. It is concluded that this 19 star subsample of the Wolf 630 moving group sample of 34 stars could represent a dispersed cluster with an [Fe/H]=−0.01 ± 0.02 and an age of 2.7 ± 0.5 Gyr. In addition, chemical abundances of Na and Al in giants are examined for indications of enhancements as observed in field giants of old open clusters; overexcitation/ionization effects are explored in the cooler dwarfs of the sample; and oxygen is derived from the infrared triplet and the forbidden line at λ6300

V474 Car: A Rare Halo RS CVn Binary in Retrograde Galactic Orbit

We report the discovery that the star V474 Car is an extremely active, high velocity halo RS CVn system. The star was originally identified as a possible pre-main sequence star in Carina, given its enhanced stellar activity, rapid rotation (10.3 days), enhanced Li, and absolute magnitude that places it above the main sequence. However, its extreme radial velocity (264 km s$^{-1}$) suggested that this system was unlike any previously known pre-MS system. Our detailed spectroscopic analysis of echelle spectra taken with the CTIO 4-m finds that V474 Car is both a spectroscopic binary with orbital period similar to the photometric rotation period, and metal poor ([Fe/H] $\simeq -$0.99). The star's Galactic orbit is extremely eccentric (e $\simeq$ 0.93) with perigalacticon of only $\sim$0.3 kpc of the Galactic center - and its eccentricity and smallness of its perigalacticon are only surpassed by $\sim$0.05%, of local F/G-type field stars. The observed characteristics are consistent with V474 Car being a high velocity, metal poor, tidally-locked chromospherically active binary (CAB), i.e.\ a halo RS CVn binary, and one of only a few such specimens known.Comment: Accepted to Astronomical Journa