# Astrophysics and Astronomy Commons™

## All Articles in Astrophysics and Astronomy

2,540 full-text articles. Page 1 of 51.

2015 The University of Western Ontario

#### Rationality Of The Spectral Action For Robertson-Walker Metrics And The Geometry Of The Determinant Line Bundle For The Noncommutative Two Torus, Asghar Ghorbanpour

##### University of Western Ontario - Electronic Thesis and Dissertation Repository

In noncommutative geometry, the geometry of a space is given via a spectral triple $(\mathcal{A,H},D)$. Geometric information, in this approach, is encoded in the spectrum of $D$ and to extract them, one should study spectral functions such as the heat trace $\Tr (e^{-tD^2})$, the spectral zeta function $\Tr(|D|^{-s})$ and the spectral action functional, $\Tr f(D/\Lambda)$.

The main focus of this thesis is on the methods and tools that can be used to extract the spectral information. Applying the pseudodifferential calculus and the heat trace techniques, in addition to computing the newer ...

2015 Cleveland State University

#### On The Detection Of Exoplanets Via Radial Velocity Doppler Spectroscopy, Joseph P. Glaser

##### The Downtown Review

Since the discovery of the first exoplanet occurred in the late 1980s, physicists and astronomers have confirmed the existence of over 1783 planets orbiting other stars. Over the years, several methods have been developed for detecting these celestial systems, but none has thus far been more successful than the use of Radial Velocity Doppler Spectroscopy. As such, this paper attempts to break down the barriers placed before new entries into the field by detailing the theoretical premise and experimental process of this most successful technique. The content enclosed is geared for the senior undergraduate student with some knowledge of vector-based ...

The Formation Of The Trajectories Of The Planets Of The Solar System, 2015 Yanbikov Vildyan Shavkyatovich

#### The Formation Of The Trajectories Of The Planets Of The Solar System, Vildyan Yanbikov

##### Vildyan Yanbikov

Процесс превращения круговой орбите планеты по эллиптической. Процесс превращения эллиптической орбите вокруг Солнца (прецессия перигелия планеты).

Alignment Of The Western And Eastern Passage Tombs At Knowth Tomb 1, 2015 Dublin Institute of Technology

#### Alignment Of The Western And Eastern Passage Tombs At Knowth Tomb 1, Frank Prendergast, Tom Ray

##### Book/Book Chapter

This report presents a summary account of two surveys undertaken by the authors to determine and interpret the alignments of the western and eastern passage tombs at Knowth, Co. Meath. The findings indicate that contrary to earlier suggestions, the eastern passage and the western passage (inner and outer) are not aligned towards sunrise and sunset respectively at the period of the vernal and autumnal equinoxes.

Geometrization Conditions For Perfect Fluids, Scalar Fields, And Electromagnetic Fields, 2015 Department of Physics, Utah State University

#### Geometrization Conditions For Perfect Fluids, Scalar Fields, And Electromagnetic Fields, Charles G. Torre, Dionisios Krongos

##### Charles G. Torre

Rainich-type conditions giving a spacetime “geometrization” of matter fields in general relativity are reviewed and extended. Three types of matter are considered: perfect fluids, scalar fields, and elec- tromagnetic fields. Necessary and sufficient conditions on a spacetime metric for it to be part of a perfect fluid solution of the Einstein equa- tions are given. Formulas for constructing the fluid from the metric are obtained. All fluid results hold for any spacetime dimension. Ge- ometric conditions on a metric which are necessary and sufficient for it to define a solution of the Einstein-scalar field equations and for- mulas for constructing ...

Rainich-Type Conditions For Perfect Fluid Spacetimes, 2014 Utah State University

#### Rainich-Type Conditions For Perfect Fluid Spacetimes, Dionisios Krongos, Charles G. Torre

##### Research Vignettes

In this worksheet we describe and illustrate a relatively simple set of new Rainich-type conditions on an n-dimensional spacetime which are necessary and sufficient for it to define a perfect fluid solution of the Einstein field equations. Procedures are provided which implement these Rainich-type conditions and which reconstruct the perfect fluid from the metric. These results provide an example of the idea of geometrization of matter fields in general relativity, which is a purely geometrical characterization of matter fields via the Einstein field equations.

Star Cluster Populations In Compact Groups Of Galaxies, 2014 The University of Western Ontario

#### Star Cluster Populations In Compact Groups Of Galaxies, Konstantin Fedotov

##### University of Western Ontario - Electronic Thesis and Dissertation Repository

In this thesis, I have explored the star cluster populations of several compact groups of galaxies, based on observations with the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope. Low velocity dispersions and high galaxy number densities, the conditions of compact groups (in particular Hickson Compact Groups), represent an environment with frequent and prolonged interactions. Such environment can trigger the formation of star cluster populations associated with specific events. The BVI study has shown that star clusters can be used as a powerful tool for studying such events triggered by mergers and tidal ...

2014 The University of Western Ontario

#### Scale-Up Methodology For Bench-Scale Slurry Photocatalytic Reactors Using Combined Irradiation And Kinetic Modelling, Patricio J. Valades Pelayo

##### University of Western Ontario - Electronic Thesis and Dissertation Repository

The present study focuses on developing a predictive methodology to scale-up a slurry annular photoreactor using a TiO2 Degussa P25 from the bench-scale to a pilot-plant scale. The bench-scale photoreactor is a Photo-CREC-Water II, a 2.65 L internally-irradiated slurry annular photocatalytic reactor. The pilot-plant scale photoreactor is a Photo-CREC Water Solar Simulator, a 9.8 L pilot-plant photoreactor, externally irradiated by eight lamps.

The adopted methodology allows the independent validation of radiative and kinetic models avoiding cross-correlation issues. The proposed approach involves two Monte Carlo methods, to model the Radiative Transfer Equation (RTE) inside each photoreactor. With this ...

Should We Love Or Hate Big Data? The Good, The Bad, And The Ugly, 2014 La Salle University

#### Should We Love Or Hate Big Data? The Good, The Bad, And The Ugly, Dennis Crossen M.Sc., Mba, Karti Puranam Phd, Madjid Tavana Phd

##### Explorer Café

No abstract provided.

The Optical Luminosity Function Of Gamma-Ray Bursts Deduced From Rotse-Iii Observations, 2014 College of Saint Benedict/Saint John's University

#### The Optical Luminosity Function Of Gamma-Ray Bursts Deduced From Rotse-Iii Observations, X. H. Cui, X. F. Wu, J. J. Wei, F. Yuan, W. K. Zheng, E. W. Liang, C. W. Akerlof, M. C. B. Ashley, H A. Flewelling, E. Göǧüş, T. Güver, Ü. Kızıloǧlu, T. A. Mckay, S. B. Pandey, E. S. Rykoff, W. Rujopakarn, B. E. Schaefer, J. C. Wheeler, Sarah A. Yost

##### Physics Faculty Publications

We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs) and those with upper limits (40 GRBs). We derive R-band fluxes for these two sub-samples 100 s after the onset of the burst. The optical LFs at 100 s are fitted by assuming that the co-moving GRB rate traces the star formation rate. While fitting the optical LFs using Monte Carlo simulations, we take into account the ...

Nasa's Search For Life Beyond The Earth, 2014 UAlbany

#### Nasa's Search For Life Beyond The Earth, John W. Delano Prof

##### Department of Atmospheric and Environmental Science Faculty Scholarship

Invited presentation (November 3, 2014 for the 119th Annual Conference of the Science Teachers Association of New York State) provides an overview of NASA's search for worlds orbiting other nearby stars on the Milky Way galaxy.

Two Stellar Populations In The Distant Milky Way Globular Cluster Ngc2419, 2014 IPFW

#### Two Stellar Populations In The Distant Milky Way Globular Cluster Ngc2419, Stephen D. Gillam Dr, Sydnee Hamrick, Christian Keating

##### Physics Faculty Presentations

The distant Milky Way globular cluster NGC2419 holds the fossil record of dark matter in the early universe. NGC2419 is 13 GYr old. It is thought that globular clusters are the remnants of giant spheroidal stars systems that formed under the gravitational influence of dark matter 13 GYr ago. Winds from supernovae and/or rotating asymptotic giant branch stars removed, in less than 1 Gyr, most of their stars and much of the gas from which new stellar generations form. These winds enriched the primordial gas in carbon+nitrogen+oxygen and helium. The amount of gas that remained de-termined how ...

2014 Washington University in St Louis

#### Tracing The Origin Of Presolar Grains: Algorithms To Parametrize Supernovae, Justin M. Finkel

##### Undergraduate Research Symposium Posters & Abstracts

Certain meteorites contain grains of stardust with isotopic compositions that suggest supernova origins. Furthermore, individual grains often contain signatures from different zones of the star, from the iron-rich core to the hydrogen- and helium-rich envelope. This implies large-scale mixing between layers, and a grain’s specific combination of isotopic ratios can be used to constrain these mixing mechanisms. To this end we have developed an algorithm which, given a grain’s set of measured isotopic ratios and a theoretical supernova model, assigns ‘mixing fractions’ to various zones of the supernova, indicating what fraction of the grain comes from each zone ...

The Role Of Subsurface Flows In Solar Surface Convection: Modeling The Spectrum Of Supergranular And Larger Scale Flows, 2014 University of Colorado, Boulder

#### The Role Of Subsurface Flows In Solar Surface Convection: Modeling The Spectrum Of Supergranular And Larger Scale Flows, J. W. Lord, R. H. Cameron, M. P. Rast, M. Rempel, T. Roudier

##### Astrophysical & Planetary Sciences Faculty Contributions

We model the solar horizontal velocity power spectrum at scales larger than granulation using a two-component approximation to the mass continuity equation. The model takes four times the density scale height as the integral (driving) scale of the vertical motions at each depth. Scales larger than this decay with height from the deeper layers. Those smaller are assumed to follow a Kolmogorov turbulent cascade, with the total power in the vertical convective motions matching that required to transport the solar luminosity in a mixing length formulation. These model components are validated using large-scale radiative hydrodynamic simulations. We reach two primary ...

2014 University of South Carolina

#### 2014 Scas Annual Meeting Program

##### Journal of the South Carolina Academy of Science

No abstract provided.

2014 University of South Carolina

#### Scas Officers And Council Members 2014-2015

##### Journal of the South Carolina Academy of Science

No abstract provided.

2014 University of South Carolina

##### Journal of the South Carolina Academy of Science

No abstract provided.

Intensities, Broadening And Narrowing Parameters In The Ν3 Band Of Methane, 2014 KAUST

#### Intensities, Broadening And Narrowing Parameters In The Ν3 Band Of Methane, Et-Touhami Es-Sebbar, Aamir Farooq

##### Dr. Et-touhami Es-sebbar

The P-branch of methane׳s ν3 band is probed to carry out an extensive study of the 2905–2908 cm−1 infrared spectral region. Absolute line intensities as well as N2-, O2-, H2-, He-, Ar- and CO2-broadening coefficients are determined for nine transitions at room temperature. Narrowing parameters due to the Dicke effect have also been investigated. A narrow emission line-width (~0.0001 cm−1) difference-frequency-generation (DFG) laser system is used as the tunable light source. To retrieve the CH4 spectroscopic parameters, Voigt and Galatry profiles were used to simulate the measured line shape of the individual transitions.

The Meaning Of Wise Colours – I. The Galaxy And Its Satellites, 2014 University of Kentucky

#### The Meaning Of Wise Colours – I. The Galaxy And Its Satellites, Robert Nikutta, Nicholas Hunt-Walker, Maia M. Nenkova, Željko Ivezić, Moshe Elitzur

##### Physics and Astronomy Faculty Publications

Through matches with the Sloan Digital Sky Survey (SDSS) catalogue we identify the location of various families of astronomical objects in WISE colour space. We identify reliable indicators that separate Galactic/local from extragalactic sources and concentrate here on the objects in our Galaxy and its closest satellites. We develop colour and magnitude criteria that are based only on WISE data to select asymptotic giant branch (AGB) stars with circumstellar dust shells, and separate them into O-rich and C-rich classes. With these criteria we produce an all-sky map for the count ratio of the two populations. The map reveals differences ...

Anomalous Organic Magnetoresistance From Competing Carrier-Spin-Dependent Interactions With Localized Electronic And Nuclear Spins, 2014 University of Iowa

#### Anomalous Organic Magnetoresistance From Competing Carrier-Spin-Dependent Interactions With Localized Electronic And Nuclear Spins, Y. Wang, N. J. Harmon, K. Sahin-Tiras, M. Wohlgenannt, M. E. Flatté

##### Department of Physics & Astronomy Publications

We describe a regime for low-field magnetoresistance in organic semiconductors, in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere. The regime is studied by the controlled addition of localized electronic spins to a material that exhibits substantial room-temperature magnetoresistance (∼20% ). Although initially the magnetoresistance is suppressed by the doping, at intermediate doping there is a regime where the magnetoresistance is insensitive to the doping level. For much greater doping concentrations the magnetoresistance is fully suppressed. The behavior is described within a theoretical model describing the effect of carrier spin dynamics on the current.