Bulletin of the American Physical Society
Joint Fall 2009 Meeting of the Texas Sections of the APS, AAPT, and SPS
Volume 54, Number 13
Thursday–Saturday, October 22–24, 2009; San Marcos, Texas
Session B4: Astronomy and Astrophysics |
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Chair: Mario Diaz, University of Texas at Brownsville Room: LBJ Student Center 3-9.1 |
Friday, October 23, 2009 10:00AM - 10:12AM |
B4.00001: Three-body recombination in ultracold plasmas: small energy transfer with large consequences D. Vrinceanu, T. Pohl, H.R. Sadeghpour Extensive Monte Carlo calculations of electron-impact induced transitions rates between highly excited Rydberg states, and ionization rate, and particle-in-cell simulation of ultracold neutral plasma evolution and cooling, are presented. While for large energy transfer, our calculations confirm the well known Mansbach and Keck's rate formulae (P. Mansbach and J. Keck, Phys. Rev. 181, 275(1969)), significant deviations for small energy transfer are found. Comparison of plasma expansion velocity in an strontium Ultracold Neutral Plasma experiment and Rydberg atom recombination in a xenon Ultracold Neutral Plasma are made, illustrating the applicability of such differences. The effects of the corrections introduced to the Mansbach and Keck rates are more pronounced for short time dynamics and almost insignificant for steady state and equilibrium quantities. [Preview Abstract] |
Friday, October 23, 2009 10:12AM - 10:24AM |
B4.00002: Quasar Jet Acceleration Nicholas Polito, David Hough We observed radio jets in six lobe-dominated quasars (LDQs) from 1995 to 2008 using the NRAO VLBA at 8.4 and 15 GHz. These observations have tracked jet component positions and velocities over that time period. There is a correlation between apparent jet speed and projected core distance in these LDQs at greater than 99 per cent confidence levels (Hough 2008, Extragalactic Jets, eds: Rector and DeYoung, ASP, p. 274). Four of our sources show this effect particularly strongly. We only tracked single jet components over relatively short distances, but the assumption of a unique velocity profile allows us to study component motion on an effective timescale of approximately 20-50 years. Results for 3C207 and 3C263 show a good fit using a constant acceleration model. The cause of such acceleration is still unknown, though ``magnetic acceleration'' by a gradient in magnetic field pressure is one possibility. [Preview Abstract] |
Friday, October 23, 2009 10:24AM - 10:36AM |
B4.00003: Investigation of Carbon Abundance in the Crab Nebula Andrea Katz, Timothy Satterfield, Gordon MacAlpine As part of a larger program to map elemental distributions in the Crab Nebula supernova remnant, we have carefully investigated the [CI] 9850 emission line as a means for measuring the gaseous carbon mass fraction.~~ Knowledge of the amount of carbon is necessary for understanding the progress of nucleosynthesis in the gas.~ Whereas this near-infrared line is very weak and not used for abundance determinations in most astronomical nebulae, it is ``anomalously'' strong in the Crab Nebula.~~ In order to determine whether or not [CI] 9850 is a reliable indicator of carbon abundance, we employed a numerical photoionization code to examine the dependence of [CI] 9850 emission on various factors, including carbon, helium, nitrogen, and oxygen abundances.~~ We also varied the ionization parameter and hydrogen density to gain insight regarding the huge difference in strength of this line in other types of objects.~ Our calculations show that [CI] 9850 is a robust indicator of carbon abundance in the Crab Nebula, where it is visible because of a high helium mass fraction and a low ionization parameter, which are not found in other nebulae. [Preview Abstract] |
Friday, October 23, 2009 10:36AM - 10:48AM |
B4.00004: Elemental Distributions in a Supernova Remnant Timothy Satterfield, Andrea Katz, Gordon MacAlpine Numerical photoionization models, created to match numerous observed spectra, are allowing us to study consistent elemental abundances and associated nuclear processing stages for gas in the Crab Nebula supernova remnant. In order to provide a better understanding of nucleosynthesis in the star that exploded, and also to provide insights into the explosive event, we are mapping spatial distributions for the important elements helium, nitrogen, oxygen, and sulfur over the observed nebular structure. We obtained and calibrated new emission-line images from the McDonald Observatory, and we developed accurate procedures involving grids of photoionization models to map the element mass fractions. These maps illustrate widely distributed and localized evidence of nuclear processing stages, such as the CNO cycle, helium burning, and oxygen burning. Each element map is uniquely different and contains important information about stellar nucleosynthesis and the explosive distribution of elements. [Preview Abstract] |
Friday, October 23, 2009 10:48AM - 11:00AM |
B4.00005: Testing a New Detection Method for RR Lyrae Variable Stars Talitha Muehlbrad, W. Lee Powell Jr., Ronald Wilhelm, Dylan Ginn, Andrew Jastram We have tested a new means of identifying RR Lyrae variable stars using large survey single-epoch, out-of-phase photometric and spectroscopic observations. The technique utilizes the marked discrepancy between (g -- r) color and Balmer-line strengths that are taken out of phase with each other. Using data collected from the 0.8-meter telescope at the McDonald Observatory for 13 halo-field stars this summer (two of which were previously confirmed RR Lyrae stars), we showed a discovery efficiency of $\sim $92{\%}. There is an overall discovery efficiency of $\sim $85{\%} using data collected from SDSS Stripe 82. The long-term goal for discovery of halo-field RR Lyrae stars is to probe the galaxy's halo substructure, and the properties of halo-field RR Lyrae stars in general. [Preview Abstract] |
Friday, October 23, 2009 11:00AM - 11:12AM |
B4.00006: Rediscovering Kepler's Third Law using NASA data Jason Keith, Paul Springsteen Kepler's three laws of planetary motion were discovered around four hundred years ago using data that was meticulously gathered by Tycho Brahe through naked eye observations. Here we will show that the same Kepler's result illustrated in his third planetary law still holds today, by using modern data from NASA. In addition, we discuss how all three of Kepler's laws of planetary motion can be derived directly from Newton's Gravitational law. [Preview Abstract] |
Friday, October 23, 2009 11:12AM - 11:24AM |
B4.00007: Chaos and the 3-Body Problem Billy Quarles, Manfred Cuntz The Circular Restricted 3-Body Problem (CR3BP) has been studied for many years. Classically it has been shown to potentially lead to chaos. However, instability and chaos are not synonymous. In exploring numerically the orbits in the CR3BP, we seek to establish criteria by determining which initial conditions will produce stable orbits, stable chaotic orbits, or unstable orbits. Using Java programming, we produced software based on computational algorithms to calculate and visually animate the orbit of the 3rd smaller body. Our software operates in a rotating reference frame allowing a clear visual representation of the planetary orbit. After establishing criteria for the short term, we look to further establish the long term stability by the use of Lyapunov exponents. By finding long term stable orbits in the CR3BP, we may be able to predict more exotic extra-solar planetary orbital configurations than what has already been observationally established. [Preview Abstract] |
Friday, October 23, 2009 11:24AM - 11:36AM |
B4.00008: Astronomical Dating of Edvard Munch's Summer Sky Paintings Ava Pope, Donald Olson Norwegian painter Edvard Munch, most famous for \emph{The Scream}, created many spectacular works depicting the skies of Norway. Our Texas State group used astronomical methods to analyze three of these paintings: \emph{Starry Night, The Storm, and Sunrise in Asgardstrand}. Astronomical dating of these paintings has some importance because the precise days when Munch visited Asgardstrand are unknown. Our research group traveled to Norway in August 2008 to find the locations from which Munch painted these three works. We then used astronomical calculations, topographical analysis, historical photographs, and weather records to determine the precise dates and times for the scenes depicted in these paintings. [Preview Abstract] |
Friday, October 23, 2009 11:36AM - 11:48AM |
B4.00009: Analyzing broadband electromagnetic pulses to geo-locate lightning Thomas Remmert Lightning discharges are taking place globally on average of 100 times per second. Systems exist to detect the location of cloud-to-ground and cloud-to-cloud discharges, but have disadvantages. Commercial units are generally expensive, have short range, and are densely packed in a small geographic location. When the strike occurs, a large electromagnetic pulse is generated. This pulse encompasses a large portion of the electromagnetic spectrum, including ELF (extremely low frequencies) and VLF (very low frequencies). Because of the low signal attenuation in these bands, the pulse is able to travel between the earth and the ionosphere great distances. By using a minimum of two stations globally, we are able to geographically locate the strike and plot it on a map in real- time. Both stations are equipped with a ELF/VLF magnetic directional antenna, a pre-amp, and computer software to perform the calculations. When a strike occurs, a voltage is induced in the antenna due to Faraday's law. This voltage is sent to a pre-amp, which filters unwanted interference, amplifies the signal, and sends it to the sound card of a computer. Complex algorithms have been designed to remove unwanted emi, including the 60Hz hum from the power lines. The software is responsible for determining the direction of the strike and the time of the strike. Once these values are calculated, this information can be shared with your partner station, and a location can be determined. [Preview Abstract] |
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