Bulletin of the American Physical Society
76th Annual Meeting of the Southeastern Section of APS
Volume 54, Number 16
Wednesday–Saturday, November 11–14, 2009; Atlanta, Georgia
Session HB: Advances in Stellar Astronomy |
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Chair: Russel White, Georgia State University Room: Frankfurt |
Friday, November 13, 2009 10:45AM - 11:15AM |
HB.00001: Evolution of the Outer Galactic Disk via Chemical Abundance Patterns Invited Speaker: I review briefly simple models to explain chemical abundance gradients in the disk of our Milky Way Galaxy, and then discuss the observations of both iron, [Fe/H], where the bracket notation refers a logarithmic scale and 0.0 represents the abundances in our Sun, and other so-called ``$\alpha $'' elements that to be produced primarily in Type II supernovae. I compare the results with the simple models, demonstrating unexpected behavior in the outer Galactic disk, and different behaviors in the old star clusters compared to the much younger Cepheid variables. I conclude that the evidence appears to support a steady growth of the Galactic disk over cosmic time. [Preview Abstract] |
Friday, November 13, 2009 11:15AM - 11:45AM |
HB.00002: Surveying the Neighborhood of the Sun Invited Speaker: In the spirit of the next human census to be carried out on planet Earth in 2010, the RECONS (Research Consortium On Nearby Stars) group at Georgia State University is gearing up to complete a decadal census of the Sun's neighbors. We'll present the latest results on the stars, brown dwarfs, and planets within 10 parsecs (about 33 light years) of the Sun and place the results into context for our Milky Way Galaxy. When compared to what we knew in 2000, our closest 300+ neighbors are significantly cooler, redder and more populated with planets than 10 years ago. [Preview Abstract] |
Friday, November 13, 2009 11:45AM - 12:15PM |
HB.00003: The Evolutionary History of the R Coronae Borealis Stars Invited Speaker: The R Coronae Borealis (RCB) stars are rare hydrogen-deficient carbon-rich supergiants, all apparently single stars which are consistent with being post-AGB stars. RCB stars undergo massive declines of up to 8 mag due to the formation of carbon dust at irregular intervals. The mechanism of dust formation around RCB stars is not well understood but the dust is thought to form in or near the atmosphere of the stars. Their rarity may stem from the fact that they are in an extremely rapid phase of the evolution or in an evolutionary phase that most stars do not undergo. Several evolutionary scenarios have been suggested to account for the RCB stars including, a merger of two white dwarfs (WDs), or a final helium shell flash in a PN central star. The large overabundance of 18O found in most of the RCB stars favors the WD merger scenario while the presence of Li in the atmospheres of four of the RCB stars favors the FF scenario. In particular, the measured isotopic abundances imply that many, if not most, RCB stars are produced by WD mergers, which may be the low-mass counterparts of the more massive mergers thought to produce type Ia supernovae. I will present recent visible and IR observations of various RCB stars obtained with HST, Spitzer and ground-based telescopes. [Preview Abstract] |
Friday, November 13, 2009 12:15PM - 12:45PM |
HB.00004: The First Three Years of Science from the CHARA Array Invited Speaker: Georgia State University's Center for High Angular Resolution Astronomy designed, built and now operates the CHARA Array on the grounds of Mt. Wilson Observatory in southern California. The Array consists of six 1-m aperture telescopes arranged in a Y-shaped configuration to comprise an interferometer operating in the visible and near infrared. With 15 baselines ranging from 34 to 331 meters, the CHARA Array possesses the longest interferometric baselines in the world. The facility achieved routine science operations in 2005 and emphasizes high spatial resolution measurements of stars to measure such parameters as stellar angular and linear diameters, effective temperatures, and limb darkening. More complicated parameters such as stellar shape, mass, and the presence of surface spots, circumstellar gas and dust in shells and in disks can also be detected. In its first three years of observations, the CHARA Array has a number of ``firsts'', most notably including the first images of the surface of a main sequence star other than the sun and the first imagery of an interacting binary star. This paper will provide an overview of selected scientific results obtained to date. [Preview Abstract] |
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