Teaching Numerical Methods In The Context Of Galaxy Mergers, 2016 California Polytechnic State University, San Luis Obispo
Teaching Numerical Methods In The Context Of Galaxy Mergers, Maria Kourjanskaia
Methods of teaching numerical methods to solve ordinary differential equations in the context of galaxy mergers were explored. The research published in a paper by Toomre and Toomre in 1972 describing the formation of galactic tails and bridges from close tidal interactions was adapted into a project targeting undergraduate physics students. Typically undergraduate physics students only take one Computational Physics class in which various techniques and algorithms are taught. Although it is important to study computational physics techniques, it is just as important to apply this knowledge to a problem that is representative of what computational physics researchers are investigating ...
The Inner Gaseous Disks Of Herbig Be Stars, 2016 The University of Western Ontario
The Inner Gaseous Disks Of Herbig Be Stars, Parshati Patel
Electronic Thesis and Dissertation Repository
Herbig Ae/Be stars are intermediate mass (~2 to 20Msun) pre-main sequence stars that inherit a circumstellar disk of dust and gas from their formation phase. The region of this disk closest to the star is entirely gaseous because dust evaporates at the high temperatures there, and this gaseous region is currently poorly understood. Using non-LTE circumstellar disk codes to model the optical and near-infrared spectra of five, early-type (B0Ve to B2Ve) Herbig Be stars obtained with the Canada-France-Hawaii telescope ESPaDOnS instrument, the density structure of each inner gaseous disks was determined and estimates of the disk masses and ...
Probing The Fitting Accuracy Of Active Galaxy Spectra, 2016 California Polytechnic State University, San Luis Obispo
Probing The Fitting Accuracy Of Active Galaxy Spectra, Aaron T. Line
Prior to this study, Dr. Vardha N. Bennert and collaborators selected a sample of ~100 local active galaxies to study the relationships between black hole mass and host galaxy properties. The broad Hβ width is necessary to determine black hole mass. This value is determined using a spectral decomposition code was scripted in IDL by Dr. Daeseong Park. The script fit spectral features and collected data for properties such as width of emission lines and continuum contribution percentages. The results were logged for further analysis.
To probe the accuracy of the fitting process, artificial spectra were created and fitted to ...
Reconciling Ag-Star Formation, The Soltan Argument, And Meier's Paradox, 2016 Kennesaw State University
Reconciling Ag-Star Formation, The Soltan Argument, And Meier's Paradox, David Garofalo, Matthew I. Kim, Damian J. Christian, Emily Hollingworth
We provide a theoretical context for understanding the recent work of Kalfountzou et al. showing that star formation is enhanced at lower optical luminosity in radio-loud quasars. Our proposal for coupling the assumption of collimated FRII quasar-jet-induced star formation with lower accretion optical luminosity also explains the observed jet power peak in active galaxies at higher redshift compared to the peak in accretion power, doing so in a way that predicts the existence of a family of radio-quiet active galactic nuclei associated with rapidly spinning supermassive black holes at low redshift, as mounting observations suggest. The relevance of this work ...
Probing Physical Conditions In The Crab Nebula With Emission Line Analysis, 2016 University of Kentucky
Probing Physical Conditions In The Crab Nebula With Emission Line Analysis, Xiang Wang
Theses and Dissertations--Physics and Astronomy
We present a range of steady-state photoionization simulations, corresponding to different assumed shell geometries and compositions, of the unseen postulated rapidly expanding outer shell to the Crab Nebula. The properties of the shell are constrained by the mass that must lie within it, and by limits to the intensities of hydrogen recombination lines. In all cases the photoionization models predict very strong emission from high ionization lines that will not be emitted by the Crab’s filaments, alleviating problems with detecting these lines in the presence of light scattered from brighter parts of the Crab. The NIR [Ne VI] λ ...
Modeling Extrasolar Trojan Asteroids In Gravitational Potentials Of Migrating Jovian-Like Planets To Inform Future Observations, Austin Hinkel
Honors Program Senior Capstone Collection
In this paper, I construct a program to map the evolution of the potential in a planet-star system where a planet with a few Jupiter masses migrates inward. Given a trojan asteroid librating around the fourth or fifth Lagrange point, the asteroid follows the evolving equipotential lines of the slowly changing potential map. As the planet and its trojan asteroids migrate inward towards the host star, the trojan asteroid librations become tighter, providing a denser “cloud” of trojan asteroids. Such a change in the density of trojan asteroids is examined with the intent to deduce the likelihood of detection via ...
Solar Modulation Of The Cosmic Ray Intensity And The Measurement Of The Cerenkov Reemission In Nova’S Liquid Scintillator, 2015 University of Tennessee - Knoxville
Solar Modulation Of The Cosmic Ray Intensity And The Measurement Of The Cerenkov Reemission In Nova’S Liquid Scintillator, Philip James Mason
The NOνA (NuMI Off-axis electron neutrino Appearance) experiment is a long baseline neutrino oscillation experiment at Fermi National Accelerator Laboratory. Its purpose is to observe the oscillation of νμ (muon neutrino) to νe (electron neutrino) and to investigate the neutrino mass hierarchy and CP violation in the neutrino sector. Two detectors have been built for this purpose, a Near Detector 300 feet underground at Fermilab, and a Far Detector, on the surface at Ash River, Minnesota.
The completion of NOνA’s Far Detector in October 2014 enabled not only the recent measurement of neutrino oscillations, but an array ...
Excess Mid-Infrared Flux: An Indicator Of Mass Loss In Cepheids?, 2015 University of Nebraska-Lincoln
Excess Mid-Infrared Flux: An Indicator Of Mass Loss In Cepheids?, Edward G. Schmidt
Edward Schmidt Publications
Spectral energy distributions for 132 classical and type II Cepheids were searched for evidence of excess flux above the photospheric level in the mid-infrared. Eight of them were found to have unambiguously strong excess emission while a further 13 showed evidence of weak emission. The presence of emission appears to be unrelated to either the pulsational amplitude or the effective temperature while strong emission is limited to stars with periods longer than 11 days, with a single exception. For the stars with strong emission we attempted to fit the energy distribution with a stellar wind model. No acceptable fit could ...
X-Ray Emission From The Giant Magnetosphere Of The Magnetic O-Type Star Ngc 1624-2, 2015 Florida Institute of Technology - Melbourne
X-Ray Emission From The Giant Magnetosphere Of The Magnetic O-Type Star Ngc 1624-2, V. Petit, D. H. Cohen, G. A. Wade, Y. Naze, S. P. Owocki, J. O. Sundqvist, A. Ud-Doula, A. Fullerton, M. Leutenegger, Marc Gagne
Geology & Astronomy Faculty Publications
No abstract provided.
Photometric Study Of The Short-Period Eclipsing Binary V441 Lac, 2015 Butler University
Photometric Study Of The Short-Period Eclipsing Binary V441 Lac, Daimei Wang, Liyun Zhang, Xianming Han, Franz Agerer, Qingfeng Pi, Shuai Wang
We present the first multi-color VRI CCD light curves of a short-period eclipsing binary star v441 Lac in this paper. We obtained our light curves on Oct. 4 and 8, 2013 at Xinglong station of National Astronomical Observatories, China. We updated the ephemeris of V441 Lac based on three new minima derived by our new observational data together with previously available light curve minima. By fitting the O−C (observed minus calculated) values of the minima, we found that the orbital period of V441 Lac exhibits an increasing trend of Ṗ=5.67(0.35)×10^-7 days/year, which ...
The First Multi-Color Photometric Study Of The Short-Period Contact Eclipsing Binary Gk Aqr, 2015 Butler University
The First Multi-Color Photometric Study Of The Short-Period Contact Eclipsing Binary Gk Aqr, Liyun Zhang, Qingfeng Pi, Xianming Han, Tongan Li, Xiliang Zhang, Hongyan Sang, Daimei Wang, Shuai Wang
We made the first VRI CCD light curves of the short-period contact eclipsing binary GK Aqr, which was observed on October 5 and 8, 2013 at Xinglong station of National Astronomical Observatories, China. The ephemeris of GK Aqr was calculated based on our two newly obtained minima and the minima that other observers obtained previously. We discovered that the orbital period of GK Aqr exhibits an increasing trend of Ṗ=2.8(0.1)×10^-7 days/year by means of fitting the O-C values of the minima. This phenomenon might be explained by mass transfer from the primary (less ...
University Scholar Series: Michael Kaufman, 2015 San Jose State University
University Scholar Series: Michael Kaufman, Michael Kaufman
University Scholar Series
On October 28, 2015, Dr. Michael Kaufman spoke in the University Scholar Series hosted by Provost Andy Feinstein at the Dr. Martin Luther King, Jr. Library. His talk was titled “H2O in Interstellar Space: How the Universe Conspires to Make Water, Water Everywhere.” Dr. Kaufman's astrophysics research focuses on the interactions and feedback between newly formed stars and the interstellar medium—the raw material from which stars form. He constructs computational models of the radiative transfer, dynamics and chemistry that occur in regions of active star formation, and uses these models to interpret observations with ground-based, airborne ...
Nitrogen Abundances In Early-Type Be Stars, 2015 The University of Western Ontario
Nitrogen Abundances In Early-Type Be Stars, Ahmed Ahmed
Electronic Thesis and Dissertation Repository
A sample of 26 Be stars from the Magnetism in Massive Stars (MiMeS) spectroscopic survey are analyzed for their photospheric nitrogen abundances in an effort to detect rotational mixing in the Be stars. Be stars are massive stars, between 3 and 20 times the mass of the Sun, that are surrounded by a thin, equatorial disk of gas that produces emission lines in their optical and near-infrared spectra. Be stars are the most rapidly-rotating stellar population on the main sequence, where stars produce energy by core hydrogen burning. New, non-LTE line transfer calculations are performed for the Nii ion, the ...
Dr. Linda French: Don’T Limit Yourself (Interview With Kelsi Singer), 2015 Illinois Wesleyan University
Dr. Linda French: Don’T Limit Yourself (Interview With Kelsi Singer), Linda French
Dr. Linda French is Professor of Physics and past Chair of the Physics Department at Illinois Wesleyan University, where she has been a professor since 2002. She received her A.B. in astronomy from Indiana University and a Ph. D. in planetary astronomy from Cornell University. Her scientific research, funded by the National Science Foundation, concerns the study of the shapes and surfaces of asteroids and comets. She is a frequent guest observer at Lowell Observatory in Arizona and at Cerro Tololo Interamerican Observatory in Chile, and is often accompanied by students on these research trips.
The V471 Tauri System: A Multi-Data-Type Probe, 2015 St. Cloud State University
The V471 Tauri System: A Multi-Data-Type Probe, Todd R. Vaccaro, Robert E. Wilson, W. Van Hamme, Dirk Terrell
Physics and Astronomy Faculty Publications
V471 Tauri, a white dwarf–red dwarf eclipsing binary ( EB) in the Hyades, is well known for stimulating development of common envelope theory, whereby novae and other cataclysmic variables form from much wider binaries by catastrophic orbit shrinkage. Our evaluation of a recent imaging search that reported negative results for a much postulated third body shows that the object could have escaped detection or may have actually been seen. The balance of evidence continues to favor a brown dwarf companion about 12 AU from the EB. A recently developed algorithm finds unified solutions from three data types. New radial velocities ...
A Coordinated X-Ray And Optical Campaign Of The Nearest Massive Eclipsing Binary, Δ Ori Aa: I. Overview Of The X-Ray Spectrum., 2015 Harvard-Smithsonian Center for Astrophysics
A Coordinated X-Ray And Optical Campaign Of The Nearest Massive Eclipsing Binary, Δ Ori Aa: I. Overview Of The X-Ray Spectrum., M. Corcoran, J. Nichols, H. Pablo, T. Shenar, A. Pollock, W. Waldron, A. Moffat, N. Richardson, C. Russell, K. Hamaguchi, D. Huenemoerder, L. Oskinova, W.-R. Hamann, Y. Nazé, R. Ignace, N. Evans, J. Lomax, J. Hoffman, K. Gayley, S. Owocki, M. Leutenegger, T. Gull, K. Hole, J. Lauer, R. Iping
We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of δ Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, δ Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, δ Ori Aa2, has a much lower X-ray luminosity than the brighter primary (δ Ori Aa1), δ Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around δ Ori Aa1 via occultation by the photosphere of, and ...
A Coordinated X-Ray And Optical Campaign Of The Nearest Massive Eclipsing Binary, Δ Orionis Aa. Iii. Analysis Of Optical Photometric (Most) And Spectroscopic (Ground Based) Variations., 2015 Université de Montréal
A Coordinated X-Ray And Optical Campaign Of The Nearest Massive Eclipsing Binary, Δ Orionis Aa. Iii. Analysis Of Optical Photometric (Most) And Spectroscopic (Ground Based) Variations., Herbert Pablo, Noel Richardson, Anthony Moffat, Michael Corcoran, Tomer Shenar, Omar Benvenuto, Jim Fuller, Yaël Nazé, Jennifer Hoffman, Anatoly Miroshnichenko, Jesús Apellániz, Nancy Evans, Thomas Eversberg, Ken Gayley, Ted Gull, Kenji Hamaguchi, Wolf-Rainer Hamann, Huib Henrichs, Tabetha Hole, Richard Ignace, Rosina Iping, Jennifer Lauer, Maurice Leutenegger, Jamie Lomax, Joy Nichols, Lida Oskinova, Stan Owocki, Andy Pollock, Christopher Russell, Wayne Waldron, Christian Buil, Thierry Garrel, Keith Graham, Bernard Heathcote, Thierry Lemoult, Dong Li, Benjamin Mauclaire, Mike Potter, Jose Ribeiro, Jaymie Matthews, Chris Cameron, David Guenther, Rainer Kuschnig, Jason Rowe, Slavek Rucinski, Dimitar Sasselov, Werner Weiss
We report on both high-precision photometry from the Microvariability and Oscillations of Stars (MOST) space telescope and ground-based spectroscopy of the triple system δ Ori A, consisting of a binary O9.5II+early-B(Aa1 and Aa2) with P=5.7 days, and a more distant tertiary(O9 IV P 400 years). This data was collected in concert with X-ray spectroscopy from the Chandra X-ray Observatory. Thanks to continuous coverage for three weeks, the MOST light curve reveals clear eclipses between Aa1 and Aa2 for the first time in non-phased data. From the spectroscopy, we have a well-constrained radial velocity (RV ...
A Coordinated X-Ray And Optical Campaign Of The Nearest Massive Eclipsing Binary, Δ Orionis Aa: Ii. X-Ray Variability., 2015 Harvard-Smithsonian Center for Astrophysics
A Coordinated X-Ray And Optical Campaign Of The Nearest Massive Eclipsing Binary, Δ Orionis Aa: Ii. X-Ray Variability., J. Nichols, D. Huenemoerder, M. Corcoran, W. Waldron, Y. Nazé, A. Pollock, A. Moffat, J. Lauer, T. Shenar, C. Russell, N. Richardson, H. Pablo, N. Evans, K. Hamaguchi, T. Gull, W.-R. Hamann, L. Oskinova, R. Ignace, Jennifer Hoffman, K. Hole, J. Lomax
We present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral data set of the δ Ori Aa binary system. The four observations, obtained with Chandra ACIS HETGS, have a total exposure time of ≈ 479 ks and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range of 5–25 Å is confirmed, with a maximum amplitude of about ±15% within a single ≈ 125 ks observation. Periods of 4.76 and 2.04 days are found in the total X-ray flux, as well as an apparent overall increase in the flux level throughout ...
Population Gradients In Globular Clusters, 2015 Indiana University - Purdue University Fort Wayne
Population Gradients In Globular Clusters, Catherine A. Pilachowski, Stephen D. Gillam, Brian J. Brondel
Physics Faculty Presentations
We report preliminary observations with the WIYN 3.5-m telescope to detect color and composition gradients in globular clusters using the red CN system at 8150 A. Globular clusters in the Milky Way are not simple stellar populations, but rather contain the products of multiple epochs of star formation. In dynamically young clusters, later generations of stars are more centrally concentrated in the clusters and are polluted with elements produced in first generation stars, showing enhanced CN band strengths. These differences suggest that multiple populations can be detected from photometric observations of the red CN system at 8100 A. The ...
Nucleosynthesis In Self-Consistent Core-Collapse Supernova Models Using Multidimensional Chimera Simulations, 2015 University of Tennessee - Knoxville
Nucleosynthesis In Self-Consistent Core-Collapse Supernova Models Using Multidimensional Chimera Simulations, James Austin Harris
Observations of nuclear abundances in core-collapse supernova (CCSN) ejecta, highlighted by γ-ray [gamma-ray] observations of the 44Ti [titanium-44] spatial distribution in the nearby supernova remnants Cassiopeia A and SN 1987A, allow nucleosynthesis calculations to place powerful constraints on conditions deep in the interiors of supernovae and their progenitor stars. This ability to probe where direct observations cannot makes such calculations an invaluable tool for understanding the CCSN mechanism. Unfortunately, despite knowing for two decades that supernovae are intrinsically multi-dimensional events, discussions of CCSN nucleosynthesis have been predominantly based on spherically symmetric (1D) models, which employ a contrived energy source ...