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Articles 4981 - 5010 of 8860

Full-Text Articles in Astrophysics and Astronomy

Galaxy Cluster Bulk Flows And Collision Velocities In Qumond, Stacy S. Mcgaugh Jun 2013

Galaxy Cluster Bulk Flows And Collision Velocities In Qumond, Stacy S. Mcgaugh

Faculty Scholarship

We examine the formation of clusters of galaxies in numerical simulations of a QUMOND cosmogony with massive sterile neutrinos. Clusters formed in these exploratory simulations develop higher velocities than those found in ΛCDM simulations. The bulk motions of clusters attain ∼1000 km s -1 by low redshift, comparable to observations whereas ΛCDM simulated clusters tend to fall short. Similarly, high pairwise velocities are common in cluster-cluster collisions like the Bullet Cluster. There is also a propensity for the most massive clusters to be larger in QUMOND and to appear earlier than in ΛCDM, potentially providing an explanation for "pink elephants" …

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Data Assimilation For Stratified Convection, Andreas Svedin, Milena C. Cuéllar, Axel Brandenburg Jun 2013

Data Assimilation For Stratified Convection, Andreas Svedin, Milena C. Cuéllar, Axel Brandenburg

Publications and Research

We show how the 3DVAR data assimilation methodology can be used in the astrophysical context of a two-dimensional convection flow. We study the way in which this variational approach finds best estimates of the current state of the flow from a weighted average of model states and observations. We use numerical simulations to generate synthetic observations of a vertical two-dimensional slice of the outer part of the solar convection zone for varying noise levels, and implement 3DVAR when the co-variance matrices are diagonal and proportional to the identity matrix. Our simulation results demonstrate the capability of 3DVAR to produce error …

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Simulation Of 810 Nm Light Propagation Through The Human Finger For Non-Invasive Blood Analysis, Nichole Millward Maughan Jun 2013

Simulation Of 810 Nm Light Propagation Through The Human Finger For Non-Invasive Blood Analysis, Nichole Millward Maughan

Theses and Dissertations

Non-invasive blood analysis devices that can measure characteristics less prominent than the oxygenation of hemoglobin are of interest in the medical community. An important step in creating these devices is to model the interaction of photons with human tissue in increasingly greater physiological detail. We have modeled, using a Monte Carlo technique, the interaction of photons through epidermis, blood and water arranged both in layers and in a homogeneous mixture. We confirm the expected linear relation between photon attenuation and material volumetric percentage in our two-layer models. We discovered that this relationship becomes non-linear in the homogeneously mixed models where …

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Constraints On Porosity And Mass Loss In O-Star Winds From The Modeling Of X-Ray Emission Line Profile Shapes, M. A. Leutenegger, David H. Cohen, J. O. Sundqvist, S. P. Owocki Jun 2013

Constraints On Porosity And Mass Loss In O-Star Winds From The Modeling Of X-Ray Emission Line Profile Shapes, M. A. Leutenegger, David H. Cohen, J. O. Sundqvist, S. P. Owocki

Physics & Astronomy Faculty Works

We fit X-ray emission line profiles in high resolution XMM-Newton and Chandra grating spectra of the early O supergiant zeta Pup with models that include the effects of porosity in the stellar wind. We explore the effects of porosity due to both spherical and flattened clumps. We find that porosity models with flattened clumps oriented parallel to the photosphere provide poor fits to observed line shapes. However, porosity models with isotropic clumps can provide acceptable fits to observed line shapes, but only if the porosity effect is moderate. We quantify the degeneracy between porosity effects from isotropic clumps and the …

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A Spectroscopic Analysis Of The Eclipsing Short-Period Binary V505 Persei And The Origin Of The Lithium Dip, Patrick Baugh, Jeremy R. King, Constantine P. Deliyannis, Ann Merchant Boesgaard Jun 2013

A Spectroscopic Analysis Of The Eclipsing Short-Period Binary V505 Persei And The Origin Of The Lithium Dip, Patrick Baugh, Jeremy R. King, Constantine P. Deliyannis, Ann Merchant Boesgaard

Publications

As a test of rotationally-induced mixing causing the well-known Li dip in older mid-F dwarfs in the local Galactic disk, we utilize high-resolution and -S/N Keck/HIRES spectroscopy to measure the Li abundance in the components of the ∼1 Gyr, [Fe/H]= −0.15 eclipsing short-period binary V505 Per. We find A(Li) ∼ 2.7 ± 0.1 and 2.4 ± 0.2 in the Teff∼6500 and 6450K primary and sec-ondary components, respectively. Previous Teff determinations and uncertainties suggest that each component is located in the midst of the Li dip. If so, their A(Li) are ≥2–5 times larger than A(Li) detections and upper limits observed …

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Observation Of Asymmetric Transport In Structures With Active Nonlinearities, N. Bender, S. Factor, J. D. Bodyfelt, Hamidreza Ramezani, D. N. Christodoulides, F. M. Ellis, T. Kottos Jun 2013

Observation Of Asymmetric Transport In Structures With Active Nonlinearities, N. Bender, S. Factor, J. D. Bodyfelt, Hamidreza Ramezani, D. N. Christodoulides, F. M. Ellis, T. Kottos

Physics & Astronomy Faculty Publications

A mechanism for asymmetric transport which is based on parity-time- symmetric nonlinearities is presented. We show that in contrast to the case of conservative nonlinearities, an increase of the complementary conductance strength leads to a simultaneous increase of asymmetry and transmittance intensity. We experimentally demonstrate the phenomenon using a pair of coupled Van der Pol oscillators as a reference system, each with complementary anharmonic gain and loss conductances, connected to transmission lines. An equivalent optical setup is also proposed. © 2013 American Physical Society.

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Astronomy Talk, Sherry Wallace Jun 2013

Astronomy Talk, Sherry Wallace

News and Events (Discontinued Series)

No abstract provided.

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70 Da White Dwarfs Identified In Lamost Pilot Survey, J K. Zhao, A L. Luo, Terry D. Oswalt, G Zhao Jun 2013

70 Da White Dwarfs Identified In Lamost Pilot Survey, J K. Zhao, A L. Luo, Terry D. Oswalt, G Zhao

Aerospace, Physics, and Space Science Faculty Publications

We present a spectroscopically identified catalog of 70 DA white dwarfs (WDs) from the LAMOST pilot survey. Thirty-five are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogs. The effective temperature and gravity of these WDs are estimated by Balmer lines fitting. Most of them are hot WDs. The cooling times and masses of these WDs are estimated by interpolation in theoretical evolution tracks. The peak of the mass distribution is found to be ∼0.6 M⊙, which is consistent with prior work in the literature. The distances of these WDs are estimated using the …

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Maximum Likelihood Analysis Of Systematic Errors In Interferometric Observations Of The Cosmic Microwave Background, Le Zhang, Ata Karakci, Paul M. Sutter, Emory F. Bunn, Andrei Korotkov, Peter Timbie, Gregory S. Tucker, Benjamin D. Wandelt Jun 2013

Maximum Likelihood Analysis Of Systematic Errors In Interferometric Observations Of The Cosmic Microwave Background, Le Zhang, Ata Karakci, Paul M. Sutter, Emory F. Bunn, Andrei Korotkov, Peter Timbie, Gregory S. Tucker, Benjamin D. Wandelt

Physics Faculty Publications

We investigate the impact of instrumental systematic errors in interferometric measurements of the cosmic microwave background (CMB) temperature and polarization power spectra. We simulate interferometric CMB observations to generate mock visibilities and estimate power spectra using the statistically optimal maximum likelihood technique. We define a quadratic error measure to determine allowable levels of systematic error that does not induce power spectrum errors beyond a given tolerance. As an example, in this study we focus on differential pointing errors. The effects of other systematics can be simulated by this pipeline in a straightforward manner. We find that, in order to accurately …

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Determining The Location Of The Coronal Line Region Within Local Active Galactic Nuclei Using [Fe Vii] Emission Line Properties, Charles Grant Showley Jun 2013

Determining The Location Of The Coronal Line Region Within Local Active Galactic Nuclei Using [Fe Vii] Emission Line Properties, Charles Grant Showley

Physics

Given a sample of 99 local AGNs, we study the characteristics of the forbidden [Fe VII] coronal line for the purpose of determining the location of the coronal line region (CLR) within the AGN. We calculate the velocity of the clouds emitting [Fe VII] using the width of the [Fe VII] emission lines compared to [O II] emission lines to establish whether the clouds are inflowing or outflowing. We plot the [Fe VII] and [O II] flux ratios against the AGNs' known black hole masses and stellar velocity dispersions in order to see if there are any correlations between them. …

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Selecting Island Pixels With A Likelihood Ratio, Jordan Tweddale Jun 2013

Selecting Island Pixels With A Likelihood Ratio, Jordan Tweddale

Physics

A new method, called the Log Likelihood Ratio (LLR), was employed in place of a Signal-to-Noise Ratio (SNR) to pick out signal pixels on the VERITAS (Very Energetic Radiation Imaging Telescope Array System ) telescopes. The LLR test was performed on both photoelectrons and timing for VERITAS to select island pixels in Stage 2 cleaning, which is where the camera image is processed to determine which pixels on the camera are signal, and which are background. The two LLRs were combined to form a final LLR, which has a numerical cut, LLR = 11.5, between signal and background pixels. The …

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Finding Rare Agn: X-Ray Number Counts Of Chandra Sources In Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Eilat Glikman, Nico Cappelluti, Francesca Civano Jun 2013

Finding Rare Agn: X-Ray Number Counts Of Chandra Sources In Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Eilat Glikman, Nico Cappelluti, Francesca Civano

Dartmouth Scholarship

We present the first results of a wide area X-ray survey within the Sloan Digital Sky Survey (SDSS) Stripe 82, a 300 deg2 region of the sky with a substantial investment in multi-wavelength coverage. We analyzed archival {\it Chandra} observations that cover 7.5 deg2 within Stripe 82 ("Stripe 82 ACX"), reaching 4.5σ flux limits of 7.9×10−16, 3.4×10−15 and 1.8×10−15 erg s−1 cm−2 in the soft (0.5-2 keV), hard (2-7 keV) and full (0.5-7 keV) bands, to find 774, 239 and 1118 X-ray sources, respectively. Three hundred twenty-one sources are detected only in the full band and 9 sources are detected …

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70 Da White Dwarfs Identified In Lamost Pilot Survey, J. K. Zhao, A. L. Luo, Terry D. Oswalt, G. Zhao Jun 2013

70 Da White Dwarfs Identified In Lamost Pilot Survey, J. K. Zhao, A. L. Luo, Terry D. Oswalt, G. Zhao

Publications

We present a spectroscopically identified catalog of 70 DA white dwarfs (WDs) from the LAMOST pilot survey. Thirty-five are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogs. The effective temperature and gravity of these WDs are estimated by Balmer lines fitting. Most of them are hot WDs. The cooling times and masses of these WDs are estimated by interpolation in theoretical evolution tracks. The peak of the mass distribution is found to be ∼0.6M, which is consistent with prior work in the literature. The distances of these WDs are estimated using the method …

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Vlt/Vimos Observations Of An Occulting Galaxy Pair : Redshifts And Effective Extinction Curve., Benne W. Holwerda, T. Boker, J. J. Dalcanton, W. C. Keel, R. S. De Jong Jun 2013

Vlt/Vimos Observations Of An Occulting Galaxy Pair : Redshifts And Effective Extinction Curve., Benne W. Holwerda, T. Boker, J. J. Dalcanton, W. C. Keel, R. S. De Jong

Faculty and Staff Scholarship

We present Very Large Telescope/Visible Multiobject Spectrograph Integral Field Unit observations of an occulting galaxy pair previously discovered in Hubble Space Telescope (HST) observations. The foreground galaxy is a low-inclination spiral disc, which causes clear attenuation features seen against the bright bulge and disc of the background galaxy. We find redshifts of z = 0.064 ± 0.003 and 0.065 for the foreground and background galaxy, respectively. This relatively small difference does not rule out gravitational interaction between the two galaxies. Emission line ratios point to a star-forming, not active galactic nuclei dominated foreground galaxy. We fit the Cardelli, Clayton and …

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Discovering Exoplanets Through Hidden Markov Model Analysis, Jon Drobny May 2013

Discovering Exoplanets Through Hidden Markov Model Analysis, Jon Drobny

Rose-Hulman Undergraduate Research Publications

The goal for the project is to develop a Hidden Markov Model for the detection and characterization of extrasolar planets through the analysis of light curves.

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An Imaging Neutron/Gamma-Ray Spectrometer, Amanda C. Madden, Peter F. Bloser, Dominique Fourguette, Liane Larocque, Matt Lewis, Jason S. Legere, Mark L. Mcconnell, Marissa Rouseau, James M. Ryan May 2013

An Imaging Neutron/Gamma-Ray Spectrometer, Amanda C. Madden, Peter F. Bloser, Dominique Fourguette, Liane Larocque, Matt Lewis, Jason S. Legere, Mark L. Mcconnell, Marissa Rouseau, James M. Ryan

Space Science Center

We present the test results of a neutron/gamma-ray imaging spectrometer for the identification and location of radioactive and special nuclear materials. Radioactive materials that could be fashioned into a radiation dispersal device typically emit gamma rays, while fissile materials such as uranium and plutonium emit both neutrons and gamma rays via spontaneous or induced fission. The simultaneous detection of neutrons and gamma rays is a clear indication of the presence of fissile material. The instrument works as a double-scatter telescope, requiring a neutron or gamma ray to undergo an interaction in two detectors to be considered a valid event. While …

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Spectro-Astrometry Of Water In Dr Tauri, Logan Brown, Matthew Troutman, Erika Gibb May 2013

Spectro-Astrometry Of Water In Dr Tauri, Logan Brown, Matthew Troutman, Erika Gibb

Physics Faculty Works

We present high-resolution, near-infrared spectro-astrometric (SA) data for the T Tauri star DR Tau using NIRSPEC at the Keck II telescope. Spectro-astrometry obtains sub-seeing spatial information from emission lines originating in a non-point source object, such as a circumstellar disk. We report the first detection of water SA signatures in a protoplanetary disk. Three water features near 3 μm were averaged together to produce the total signal analyzed. Using a disk model, we constrained the position angle of the disk (~140°), the inclination of the disk (~13°), and the emitting region of the emission lines (~0.056-0.38 AU).

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Narrow-Line Region Gas Kinematics Of 24 264 Optically Selected Agn: The Radio Connection, J. R. Mullaney, D. M. Alexander, S. Fine, A. D. Goulding, C. M. Harrison, R. C. Hickox May 2013

Narrow-Line Region Gas Kinematics Of 24 264 Optically Selected Agn: The Radio Connection, J. R. Mullaney, D. M. Alexander, S. Fine, A. D. Goulding, C. M. Harrison, R. C. Hickox

Dartmouth Scholarship

Using a sample of 24 264 optically selected active galactic nuclei (AGNs) from the SDSS DR7 data base, we characterize how the profile of the [O iii] λ5007 emission line relates to bolometric luminosity (LAGN), Eddington ratio, radio loudness, radio luminosity (L1.4 GHz) and optical class (i.e. broad/narrow-line Seyfert 1, type 2) to determine what drives the kinematics of this kpc-scale line emitting gas. First, we use spectral stacking to characterize how the average [O iii] λ5007 profile changes as a function of these five variables. After accounting for the known correlation between L …

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Discontinuities And Alfvenic Fluctuations In The Solar Wind, G. Paschmann, S. Haaland, B. Sonnerup, T. Knetter May 2013

Discontinuities And Alfvenic Fluctuations In The Solar Wind, G. Paschmann, S. Haaland, B. Sonnerup, T. Knetter

Dartmouth Scholarship

We examine the Alfvenicity of a set of 188 solar wind directional discontinuities (DDs) identified in the Cluster data from 2003 by Knetter (2005), with the objective of separating rotational discontinuities (RDs) from tangential ones (TDs). The DDs occurred over the full range of solar wind velocities and magnetic shear angles. By performing the Walen test in the de Hoffmann–Teller (HT) frame, we show that 77 of the 127 crossings for which a good HT frame was found had plasma flow speeds exceeding 80 % of the Alfven speed at an average angular deviation of 7.7◦; 33 cases had speeds …

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Infrared Spectroscopy Of Symbiotic Stars. Ix. D-Type Symbiotic Novae, Kenneth H. Hinkle, Francis C. Fekel, Richard R. Joyce, Peter R. Wood May 2013

Infrared Spectroscopy Of Symbiotic Stars. Ix. D-Type Symbiotic Novae, Kenneth H. Hinkle, Francis C. Fekel, Richard R. Joyce, Peter R. Wood

Information Systems and Engineering Management Research Publications

Time-series spectra of the near-infrared 1.6 μm region have been obtained for five of the six known D-type symbiotic novae. The spectra map the pulsation kinematics of the Mira component in the Mira–white dwarf binary system and provide the center-of-mass velocity for the Mira. No orbital motion is detected in agreement with previous estimates of orbital periods ≳100 yr and semimajor axes ∼50 AU. The 1–5 μm spectra of the Miras show line weakening during dust obscuration events. This results from scattering and continuum emission by 1000 K dust. In the heavily obscured HM Sge system the 4.6 μm CO …

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Estimations Of The Magnetic Field Strength In The Torus Of Ic 5063 Using Near-Infrared Polarimetry, E. Lopez-Rodriguez, C. Packham, S. Young, Moshe Elitzur, N. A. Levenson, R. E. Mason, C. Ramos Almeida, A. Alonso-Herrero, T. J. Jones, E. Perlman May 2013

Estimations Of The Magnetic Field Strength In The Torus Of Ic 5063 Using Near-Infrared Polarimetry, E. Lopez-Rodriguez, C. Packham, S. Young, Moshe Elitzur, N. A. Levenson, R. E. Mason, C. Ramos Almeida, A. Alonso-Herrero, T. J. Jones, E. Perlman

Physics and Astronomy Faculty Publications

An optically and geometrically thick torus obscures the central engine of active galactic nuclei (AGN) from some lines of sight. From a magnetohydrodynamical framework, the torus can be considered to be a particular region of clouds surrounding the central engine where the clouds are dusty and optically thick. In this framework, the magnetic field plays an important role in the creation, morphology and evolution of the torus. If the dust grains within the clouds are assumed to be aligned by paramagnetic alignment, then the ratio of the intrinsic polarization and visual extinction, P(per cent)/Av, is a …

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The X-Ray Properties Of Optically Selected Clusters Of Galaxies, A. K. Hicks, G. W. Pratt, M. Donahue, E. Ellingson, M. Gladders, H. Böhringer, H. K. C. Yee, Renbin Yan, J. H. Croston, D. G. Gilbank May 2013

The X-Ray Properties Of Optically Selected Clusters Of Galaxies, A. K. Hicks, G. W. Pratt, M. Donahue, E. Ellingson, M. Gladders, H. Böhringer, H. K. C. Yee, Renbin Yan, J. H. Croston, D. G. Gilbank

Physics and Astronomy Faculty Publications

We present the results of Chandra and Suzaku X-ray observations of nine moderate-redshift (0.16 < z < 0.42) clusters discovered via the Red-sequence Cluster Survey (RCS). Surface brightness profiles are fitted to β-models, gas masses are determined, integrated spectra are extracted within R2500, and X-ray temperatures and luminosities are inferred. TheLX–TX relationship expected from self-similar evolution is tested by comparing this sample to our previous X-ray investigation of nine high-redshift (0.6 < z < 1.0) optically selected clusters. We find that optically selected clusters are systematically less luminous than X-ray selected clusters of similar X-ray temperature at both moderate and high z. We are unable to constrain evolution in the LX–TX relation with these data, but find it consistent with no evolution, within relatively large uncertainties. To investigate selection effects, we compare the X-ray properties of our sample to those of clusters in the …

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Improved Orbital Parameters And Transit Monitoring For Hd 156846b, S. R. Kane, A. W. Howard, G. Pilyavsky, S. Mahadevan, G. W. Henry, K. Von Braun, D. R. Ciardi, D. Dragomir, D. A. Fischer, Eric L.N. Jensen, G. Laughlin, S. V. Ramirez, J. T. Wright May 2013

Improved Orbital Parameters And Transit Monitoring For Hd 156846b, S. R. Kane, A. W. Howard, G. Pilyavsky, S. Mahadevan, G. W. Henry, K. Von Braun, D. R. Ciardi, D. Dragomir, D. A. Fischer, Eric L.N. Jensen, G. Laughlin, S. V. Ramirez, J. T. Wright

Physics & Astronomy Faculty Works

HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a period of 359.55 days. The pericenter passage at a distance of 0.16 AU is nearly aligned to our line of sight, offering an enhanced transit probability of 5.4% and a potentially rich probe of the dynamics of a cool planetary atmosphere impulsively heated during close approach to a bright star (V = 6.5). We present new radial velocity (RV) and photometric measurements of this star as part of the Transit Ephemeris Refinement and Monitoring Survey. The RV measurements from the Keck-High Resolution Echelle Spectrometer …

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Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Iii. Tangential Motions Using Astrodrizzle Images, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert May 2013

Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Iii. Tangential Motions Using Astrodrizzle Images, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert

Physics and Astronomy Faculty Publications

We have been able to compare with astrometric precision AstroDrizzle processed images of NGC 6720 (the Ring Nebula) made using two cameras on the Hubble Space Telescope. The time difference of the observations was 12.925 yr. This large time base allowed the determination of tangential velocities of features within this classic planetary nebula. Individual features were measured in [N II] images as were the dark knots seen in silhouette against background nebular [O III] emission. An image magnification and matching technique was also used to test the accuracy of the usual assumption of homologous expansion. We found that homologous …

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The Prevalence Of Dust On The Exoplanet Hd 189733b From Hubble And Spitzer Observations, Frederic Pont, David K. Sing, Neale P. Gibson, Suzanne Aigrain, Gregory W. Henry, Nawal Husnoo May 2013

The Prevalence Of Dust On The Exoplanet Hd 189733b From Hubble And Spitzer Observations, Frederic Pont, David K. Sing, Neale P. Gibson, Suzanne Aigrain, Gregory W. Henry, Nawal Husnoo

Information Systems and Engineering Management Research Publications

The hot Jupiter HD 189733b is the most extensively observed exoplanet. Its atmosphere has been detected and characterized in transmission and eclipse spectroscopy, and its phase curve measured at several wavelengths. This paper brings together the results of our campaign to obtain the complete transmission spectrum of the atmosphere of this planet from UV to infrared with the Hubble Space Telescope, using the STIS, ACS and WFC3 instruments. We provide a new tabulation of the transmission spectrum across the entire visible and infrared range. The radius ratio in each wavelength band was re-derived, where necessary, to ensure a consistent treatment …

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Reactive Intermediates In Hypoxia-Selective Dna Damage., Olivia Miller May 2013

Reactive Intermediates In Hypoxia-Selective Dna Damage., Olivia Miller

Undergraduate Honors Theses

A group of prospective drugs with the aromatic di-N-oxide (ANO) functionality as the common feature are currently undergoing testing for the ability to selectively target tumors surrounded by normal tissues. It has been long recognized that the mechanism of biological activity of these drugs involves DNA damage by free radical species generated through one-electron reduction, although the exact nature of the reactive intermediate responsible for DNA damage remains uncertain. It is believed, however, that one of the key factors defining, in particular, hypoxic selectivity of these drugs is the rate of N-O bond scission in the one-electron reduced intermediate. In …

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Accurate Hyperfine Coupling Calculations Of Radiation Induced Dna Constituent Radicals Using Density Functional Theory., Xiqiao Wang May 2013

Accurate Hyperfine Coupling Calculations Of Radiation Induced Dna Constituent Radicals Using Density Functional Theory., Xiqiao Wang

Undergraduate Honors Theses

Previous density functional theory (DFT) calculations of hyperfine coupling constants (HFCC) on single nucleic acid base radicals agree well with the EPR/ENDOR experiments’ values on radiation induced nucleic acid constituents radicals, except for four problem cases,1 namely the N1-deprotonated cytosine cation radical, the native guanine cation radical, the N3-deprotonated 5’-dCMP cation radical and the N7-H, O6-H protonated 5’-GMP anion. The main effort of the present work is to address these four discrepancies by using the highly parameterized density functional M05/6-2X and by including the crystalline environment’s H-bonding effects in the calculations. The geometries of the four model radicals are optimized …

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Host Star Properties And Transit Exclusion For The Hd 38529 Planetary System, G. W. Henry, S. R. Kane, S. X. Wang, T. S. Boyajian, K. Von Braun, D. R. Ciardi, D. Dragomir, C. Farrington, D. A. Fischer, N. R. Hinkel, A. W. Howard, Eric L.N. Jensen, G. Laughlin, S. Mahadevan, G. Pilyavsky May 2013

Host Star Properties And Transit Exclusion For The Hd 38529 Planetary System, G. W. Henry, S. R. Kane, S. X. Wang, T. S. Boyajian, K. Von Braun, D. R. Ciardi, D. Dragomir, C. Farrington, D. A. Fischer, N. R. Hinkel, A. W. Howard, Eric L.N. Jensen, G. Laughlin, S. Mahadevan, G. Pilyavsky

Physics & Astronomy Faculty Works

The transit signature of exoplanets provides an avenue through which characterization of exoplanetary properties may be undertaken, such as studies of mean density, structure, and atmospheric composition. The Transit Ephemeris Refinement and Monitoring Survey is a program to expand the catalog of transiting planets around bright host stars by refining the orbits of known planets discovered with the radial velocity technique. Here we present results for the HD 38529 system. We determine fundamental properties of the host star through direct interferometric measurements of the radius and through spectroscopic analysis. We provide new radial velocity measurements that are used to improve …

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Planet Hunters: A Transiting Circumbinary Planet In A Quadruple Star System, Megan E. Schwamb, William C. Keel May 2013

Planet Hunters: A Transiting Circumbinary Planet In A Quadruple Star System, Megan E. Schwamb, William C. Keel

Aerospace, Physics, and Space Science Faculty Publications

We report the discovery and confirmation of a transiting circumbinary planet (PH1b) around KIC 4862625, an eclipsing binary in the Kepler field. The planet was discovered by volunteers searching the first six Quarters of publicly available Kepler data as part of the Planet Hunters citizen science project. Transits of the planet across the larger and brighter of the eclipsing stars are detectable by visual inspection every ∼137 days, with seven transits identified in Quarters 1–11. The physical and orbital parameters of both the host stars and planet were obtained via a photometric-dynamical model, simultaneously fitting both the measured radial velocities …

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Cluster Expansion Models Via Bayesian Compressive Sensing, Lance Jacob Nelson May 2013

Cluster Expansion Models Via Bayesian Compressive Sensing, Lance Jacob Nelson

Theses and Dissertations

The steady march of new technology depends crucially on our ability to discover and design new, advanced materials. Partially due to increases in computing power, computational methods are now having an increased role in this discovery process. Advances in this area speed the discovery and development of advanced materials by guiding experimental work down fruitful paths. Density functional theory (DFT)has proven to be a highly accurate tool for computing material properties. However, due to its computational cost and complexity, DFT is unsuited to performing exhaustive searches over many candidate materials or for extracting thermodynamic information. To perform these types of …

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