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Articles 5491 - 5520 of 8864

Full-Text Articles in Astrophysics and Astronomy

A Deep Search For The Host Galaxies Of Gamma-Ray Bursts With No Detected Optical Afterglow, Andrea Rossi, E E. Gonsalves Jan 2012

A Deep Search For The Host Galaxies Of Gamma-Ray Bursts With No Detected Optical Afterglow, Andrea Rossi, E E. Gonsalves

Aerospace, Physics, and Space Science Faculty Publications

Context. Gamma-ray bursts (GRBs) can provide information about star formation at high redshifts. Even in the absence of a bright optical/near-infrared/radio afterglow, the high detection rate of X-ray afterglows by Swift/XRT and its localization precision of 2–3 arcsec facilitates the identification and the study of GRB host galaxies. Aims. We focus on the search for the host galaxies of 17 bursts with arcsec-sized XRT error circles but no detected long-wavelength afterglow, in spite of their deep and rapid follow-up observations. Three of these events can also be classified as truly dark bursts, i.e., the observed upper limit on the optical …

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Agile Detection Of Cygnus X-3 Γ-Ray Active States During The Period Mid-2009/Mid-2010, A Bulgarelli, Diana C. Hannikainen Jan 2012

Agile Detection Of Cygnus X-3 Γ-Ray Active States During The Period Mid-2009/Mid-2010, A Bulgarelli, Diana C. Hannikainen

Aerospace, Physics, and Space Science Faculty Publications

Context. Cygnus X-3 (Cyg X-3) is a well-known microquasar producing variable emission at all wavelengths. Cyg X-3 is a prominent X-ray binary producing relativistic jets, and studying its high energy emission is crucial for the understanding of the fundamental acceleration processes in accreting compact objects. Aims. Our goal is to study extreme particle acceleration and γ-ray production above 100 MeV during special spectral states of Cyg X-3 usually characterized by a low hard X-ray flux and enhanced soft X-ray states. Methods. We observed Cyg X-3 with the AGILE satellite in extended time intervals from 2009 Jun.–Jul., and 2009 Nov.–2010 Jul. …

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International Observational Campaigns Of The Last Two Eclipses In Ee Cephei: 2003 And 2008/9, Cezary Galan, Peter Németh Jan 2012

International Observational Campaigns Of The Last Two Eclipses In Ee Cephei: 2003 And 2008/9, Cezary Galan, Peter Németh

Aerospace, Physics, and Space Science Faculty Publications

Context. EE Cep is an unusual long-period (5.6 yr) eclipsing binary discovered during the mid-twentieth century. It undergoes almost-grey eclipses that vary in terms of both depth and duration at different epochs. The system consists of a Be type star and a dark dusty disk around an invisible companion. EE Cep together with the widely studied ε Aur are the only two known cases of long-period eclipsing binaries with a dark, dusty disk component responsible for periodic obscurations. Aims. Two observational campaigns were carried out during the eclipses of EE Cep in 2003 and 2008/9 to verify whether the eclipsing …

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Deviation From Quark Number Scaling Of The Anisotropy Parameter V₂ Of Pions, Kaons, And Protons In Au+Au Collisions At √S Nn=200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann, Phenix Collaboration Jan 2012

Deviation From Quark Number Scaling Of The Anisotropy Parameter V₂ Of Pions, Kaons, And Protons In Au+Au Collisions At √S Nn=200 Gev, Andrew Marshall Adare, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann, Phenix Collaboration

Aerospace, Physics, and Space Science Faculty Publications

Measurements of the anisotropy parameter v₂ of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum pT, and transverse kinetic energy KET at midrapidity (|η|<0.35) in Au+Au collisions at √sNN=200 GeV are presented. Pions and protons are identified up to pT= 6 GeV/c, and kaons up to pT= 4 GeV/c, by combining information from time-of-flight and aerogel Čerenkov detectors in the PHENIX Experiment. The scaling of v₂ with the number of valence quarks (nq) has been studied in different centrality bins as a function of transverse momentum and transverse kinetic energy. A deviation from previously observed quark-number scaling is observed at large values of KET/nq in noncentral Au+Au collisions (20-60%), but this scaling remains valid in central collisions (0-10%).

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Forty-Year Calibrated Record Of Earth-Reflected Radiance From Landsat: A Review, Brian L. Markham, Dennis L. Helder Jan 2012

Forty-Year Calibrated Record Of Earth-Reflected Radiance From Landsat: A Review, Brian L. Markham, Dennis L. Helder

United States National Aeronautics and Space Administration: Publications

Sensors on Landsat satellites have been collecting images of the Earth's surface for nearly 40 years. These images have been invaluable for characterizing and detecting changes in the land cover and land use of the world. Although initially conceived as primarily picture generating sensors, even the early sensors were radiometrically calibrated and spectrally characterized prior to launch and incorporated some capabilities to monitor their radiometric calibration once on orbit. Recently, as the focus of studies has shifted to monitoring Earth surface parameters over significant periods of time, serious attention has been focused toward bringing the data from all these sensors …

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The Venus "Shell-Over-Star" Hieroglyph And Maya Warfare: An Examination Of The Interpretation Of A Mayan Symbol, Claudia Ann Voit Jan 2012

The Venus "Shell-Over-Star" Hieroglyph And Maya Warfare: An Examination Of The Interpretation Of A Mayan Symbol, Claudia Ann Voit

Wayne State University Theses

For decades, Maya scholars have associated the Mayan ―Shell-Star‖ (also referred to as ―Star-War‖) hieroglyph with Maya warfare. Put forward by scholars such as Floyd Lounsbury and David Kelley, and later advanced by Linda Schele, David Freidel, Ian Graham, Peter Matthews, Anthony Aveni and others, there are now dozens of published articles and chapters relating the hieroglyph to Venus and warfare. Venus is one of the most notable celestial objects outside of the Sun and Moon and was highly visible to the inhabitants of the Maya world. The Dresden Codex (an astronomical almanac) contains important information about the planet Venus, …

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The Influence Of Soft Spectral Components On The Structure And Stability Of Warm Absorbers In Active Galactic Nuclei, Susmita Chakravorty, Ranjeev Misra, Martin Elvis, Ajit K. Kembhavi, Gary J. Ferland Jan 2012

The Influence Of Soft Spectral Components On The Structure And Stability Of Warm Absorbers In Active Galactic Nuclei, Susmita Chakravorty, Ranjeev Misra, Martin Elvis, Ajit K. Kembhavi, Gary J. Ferland

Physics and Astronomy Faculty Publications

The radiation from the central regions of active galactic nuclei, including that from the accretion disc surrounding the black hole, is likely to peak in the extreme-ultraviolet ∼13–100 eV. However, due to Galactic absorption, we are limited to constrain the physical properties, i.e. the black hole mass and the accretion rate, from what observations we have below ∼10 eV or above ∼100 eV. In this paper, we predict the thermal and ionization states of warm absorbers as a function of the shape of the unobservable continuum. In particular we model an accretion disc at kTin∼ 10 eV and …

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Herschel Observations Of Extended Atomic Gas In The Core Of The Perseus Cluster, R. Mittal, J. B. R. Oonk, Gary J. Ferland, A. C. Edge, C. P. O'Dea, S. A. Baum, J. T. Whelan, R. M. Johnstone, F. Combes, P. Salomé, A. C. Fabian, G. R. Tremblay, M. Donahue, Russell H. H. Jan 2012

Herschel Observations Of Extended Atomic Gas In The Core Of The Perseus Cluster, R. Mittal, J. B. R. Oonk, Gary J. Ferland, A. C. Edge, C. P. O'Dea, S. A. Baum, J. T. Whelan, R. M. Johnstone, F. Combes, P. Salomé, A. C. Fabian, G. R. Tremblay, M. Donahue, Russell H. H.

Physics and Astronomy Faculty Publications

We present Herschel observations of the core of the Perseus cluster of galaxies. Especially intriguing is the network of filaments that surround the brightest cluster galaxy, NGC 1275, previously imaged extensively in Hα and CO. In this work, we report detections of far-infrared (FIR) lines, in particular, [C II] 158, [O I] 63, [N II] 122, [O IB] 145 and [O III] 88  μm, withHerschel. All lines are spatially extended, except [O III], with the [C II] line emission extending up to 25 kpc from the core. [C II] emission is found to be co-spatial with Hα and …

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Multiphase Signatures Of Active Galactic Nucleus Feedback In Abell 2597, G. R. Tremblay, C. P. O'Dea, S. A. Baum, T. E. Clarke, C. L. Sarazin, J. N. Bregman, F. Combes, M. Donahue, A. C. Edge, A. C. Fabian, Gary J. Ferland, B. R. Mcnamara, R. Mittal, J. B. R. Oonk, A. C. Quillen, H. R. Russell, J. S. Sanders, P. Salomé, G. M. Voit, R. J. Wilman, M. W. Wise Jan 2012

Multiphase Signatures Of Active Galactic Nucleus Feedback In Abell 2597, G. R. Tremblay, C. P. O'Dea, S. A. Baum, T. E. Clarke, C. L. Sarazin, J. N. Bregman, F. Combes, M. Donahue, A. C. Edge, A. C. Fabian, Gary J. Ferland, B. R. Mcnamara, R. Mittal, J. B. R. Oonk, A. C. Quillen, H. R. Russell, J. S. Sanders, P. Salomé, G. M. Voit, R. J. Wilman, M. W. Wise

Physics and Astronomy Faculty Publications

We present new Chandra X-ray observations of the brightest cluster galaxy (BCG) in the cool-core cluster Abell 2597 (z= 0.0821). The data reveal an extensive kpc-scale X-ray cavity network as well as a 15-kpc filament of soft-excess gas exhibiting strong spatial correlation with archival Very Large Array radio data. In addition to several possible scenarios, multiwavelength evidence may suggest that the filament is associated with multiphase (103–107 K) gas that has been entrained and dredged-up by the propagating radio source. Stemming from a full spectral analysis, we also present profiles and 2D spectral maps of …

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A Reverberation Lag For The High-Ionization Component Of The Broad-Line Region In The Narrow-Line Seyfert 1 Mrk 335, C. J. Grier, B. M. Peterson, R. W. Pogge, K. D. Denney, M. C. Bentz, Paul Martini, S. G. Sergeev, S. Kaspi, Y. Zu, C. S. Kochanek, B. J. Shappee, C. Araya Salvo, T G. Beatty, J. C. Bird, D. J. Bord, G. A. Borman, X. Che, C. Chen Jan 2012

A Reverberation Lag For The High-Ionization Component Of The Broad-Line Region In The Narrow-Line Seyfert 1 Mrk 335, C. J. Grier, B. M. Peterson, R. W. Pogge, K. D. Denney, M. C. Bentz, Paul Martini, S. G. Sergeev, S. Kaspi, Y. Zu, C. S. Kochanek, B. J. Shappee, C. Araya Salvo, T G. Beatty, J. C. Bird, D. J. Bord, G. A. Borman, X. Che, C. Chen

Dartmouth Scholarship

We present the first results from a detailed analysis of photometric and spectrophotometric data on the narrow-line Seyfert 1 (NLS1) galaxy Mrk 335, collected over a 120 day span in the fall of 2010. From these data we measure the lag in the He ii λ 4686 broad emission line relative to the optical continuum to be 2.7 °æ 0.6 days and the lag in the Hβλ 4861 broad emission line to be 13.9 °æ 0.9 days. Combined with the line width, the He ii lag yields a black hole mass MBH = (2. 6 °æ 0. 8) °ø 107M …

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Quantization And Discretization At Large Scales, Florentin Smarandache, Victor Christianto, Pavel Pintr Jan 2012

Quantization And Discretization At Large Scales, Florentin Smarandache, Victor Christianto, Pavel Pintr

Branch Mathematics and Statistics Faculty and Staff Publications

The ongoing search of extrasolar planets is one of the most attractive fields of research in astrophysics and astronomy. Up to now, 360 extrasolar planets have been discovered near stars with similar mass as the Sun. There is also discovery related to the so-called Earth-like planets. With regards to these discoveries, one intriguing question is whether there is relationship between orbit distance of the planets and their stars. Various formulas have been suggested since 1990s, and they suggest that there may be reason to accept quantization of distances of those planets both in our solar system and also in extrasolar …

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Vacuum, Space-Time, Matter And The Models Of Smarandache Geometry, Florentin Smarandache, Hu Chang-Wei Jan 2012

Vacuum, Space-Time, Matter And The Models Of Smarandache Geometry, Florentin Smarandache, Hu Chang-Wei

Branch Mathematics and Statistics Faculty and Staff Publications

Many fundamental concepts in physics remain unsolved:  What is time? Is it pure relative?  What is the vacuum? Is it void space or special medium?  What is mass? Can it be created? I believe that physicists have not got definite answers for the above questions. Isaac Newton said: I was like a boy playing on the sea-shore, and diverting myself now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. For instance, we still do not know what the clear definition of time …

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Table Of Contents Jan 2012

Table Of Contents

Journal of the South Carolina Academy of Science

No abstract provided.

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Scas Officers And Council Members 2011 - 2012 Jan 2012

Scas Officers And Council Members 2011 - 2012

Journal of the South Carolina Academy of Science

No abstract provided.

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Stellar Astrophysics With Undergraduate Students, Saul J. Adelman Jan 2012

Stellar Astrophysics With Undergraduate Students, Saul J. Adelman

Journal of the South Carolina Academy of Science

No abstract provided.

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The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer Jan 2012

The Allen Telescope Array Search For Electrostatic Discharges On Mars, Marin M. Anderson, Andrew P.V. Siemion, William C. Barott, Geoffery C. Bower, Gregory T. Delory, Imke De Pater, Dan Werthimer

Department of Electrical Engineering and Computer Science - Daytona Beach

The Allen Telescope Array was used to monitor Mars between 2010 March 9 and June 2, over a total of approximately 30 hr, for radio emission indicative of electrostatic discharge. The search was motivated by the report from Ruf et al. of the detection of non-thermal microwave radiation from Mars characterized by peaks in the power spectrum of the kurtosis, or kurtstrum, at 10 Hz, coinciding with a large dust storm event on 2006 June 8. For these observations, we developed a wideband signal processor at the Center for Astronomy Signal Processing and Electronics Research. This 1024 channel spectrometer calculates …

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Everything Is Entangled, Roman V. Buniy, Stephen D. H. Hsu Jan 2012

Everything Is Entangled, Roman V. Buniy, Stephen D. H. Hsu

Mathematics, Physics, and Computer Science Faculty Articles and Research

We show that big bang cosmology implies a high degree of entanglement of particles in the universe. In fact, a typical particle is entangled with many particles far outside our horizon. However, the entanglement is spread nearly uniformly so that two randomly chosen particles are unlikely to be directly entangled with each other - the reduced density matrix describing any pair is likely to be separable.

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Toward Solving The Cosmological Constant Problem By Embedding, Roman V. Buniy, Thomas W. Kephart Jan 2012

Toward Solving The Cosmological Constant Problem By Embedding, Roman V. Buniy, Thomas W. Kephart

Mathematics, Physics, and Computer Science Faculty Articles and Research

The typical scalar field theory has a cosmological constant problem. We propose a generic mechanism by which this problem is avoided at tree level by embedding the theory into a larger theory. The metric and the scalar field coupling constants in the original theory do not need to be fine-tuned, while the extra scalar field parameters and the metric associated with the extended theory are fine-tuned dynamically. Hence, no fine-tuning of parameters in the full Lagrangian is needed for the vacuum energy in the new physical system to vanish at tree level. The cosmological constant problem can be solved if …

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Interacting Dark Energy Models And The Cosmic Coincidence Problem, H. Shojaei, C. Smith, D. Waters Jan 2012

Interacting Dark Energy Models And The Cosmic Coincidence Problem, H. Shojaei, C. Smith, D. Waters

Journal of the Arkansas Academy of Science

Interacting dark energy models have been employed to study the behavior of dark energy and matter in the presence of an interaction between the two. One of the successful aspects of these models is how they explain the cosmic coincidence problem. In this work we consider a specific interaction to study the behavior of dark energy and matter through the history of evolution.

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Variability In X-Ray Line Ratios In Helium-Like Ions Of Massive Stars: The Radiation-Driven Case., K. Hole, Richard Ignace Jan 2012

Variability In X-Ray Line Ratios In Helium-Like Ions Of Massive Stars: The Radiation-Driven Case., K. Hole, Richard Ignace

ETSU Faculty Works

Line ratios in "fir" triplets of helium-like ions have proven to be a powerful diagnostic of conditions in X-ray emitting gas surrounding massive stars. Recent observations indicate that these ratios can be variable with time. The possible causes of variation in line ratios are limited: changes in the radiation field or changes in density, and changes in mass-loss or geometry. In this paper, we investigate the ability of changes in the radiation field to induce variability in the ratio R=f/i. To isolate the radiative effect, we use a heuristic model of temperature and radius changes in variable stars in the …

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The Legendre Transform Of The Holst Action, Caixia Gao Jan 2012

The Legendre Transform Of The Holst Action, Caixia Gao

Electronic Theses and Dissertations

I start with a short introduction on 3+1 ADM form and the tetrad form of General Relativity, then I review the Legendre transform of the Einstein-Hilbert action and the Palatini action. The Holst action is a generalization of the Palatini action by including a topological term. I derive Ashtekar's connection form directly from this action by doing the Legendre transformation rather than by a canonical transformation in the usual phase space. This is done in both Remmanian signature with half-flat connection and Lorentz signature with general Barbero-Immirzi parameter.

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Multi-Color Observations Of Short Grb Afterglows: 20 Events Observed Between 2007 And 2010, A. Nicuesa Guelbenzu, S. Klose, J. Greiner, D.A. Kann, T. Krühler, A. Rossi, S. Schulze, P.M.J. Afonso, J. Elliott, R. Filgas, D.H. Hartmann, A. Küpcü Yoldas, S. Mcbreen, M. Nardini, F. Olivares E., A. Rau, S. Schmidl, P. Schady, V. Sudilovsky, Adria Updike, A. Yoldas Jan 2012

Multi-Color Observations Of Short Grb Afterglows: 20 Events Observed Between 2007 And 2010, A. Nicuesa Guelbenzu, S. Klose, J. Greiner, D.A. Kann, T. Krühler, A. Rossi, S. Schulze, P.M.J. Afonso, J. Elliott, R. Filgas, D.H. Hartmann, A. Küpcü Yoldas, S. Mcbreen, M. Nardini, F. Olivares E., A. Rau, S. Schmidl, P. Schady, V. Sudilovsky, Adria Updike, A. Yoldas

Arts & Sciences Faculty Publications

No abstract provided.

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A Deep Search For The Host Galaxies Of Gamma-Ray Bursts With No Detected Optical Afterglow, A. Rossi, S. Klose, P. Ferrero, J. Greiner, L.A. Arnold, E. Gonsalves, D.H. Hartmann, Adria Updike, D.A. Kann, T. Krühler, E. Palazzi, S. Savaglio, S. Schulze, P.M.J. Afonso, L. Amati, A.J. Castro-Tirado, C. Clemens, R. Filgas, J. Gorosabel, L.K. Hunt, A. Küpcü Yoldas, N. Masetti, M. Nardini, A. Nicuesa Guelbenzu, F.E. Olivares, E. Pian, A. Rau, P. Schady, S. Schmidl, A. Yoldas, A. De Ugarte Postigo Jan 2012

A Deep Search For The Host Galaxies Of Gamma-Ray Bursts With No Detected Optical Afterglow, A. Rossi, S. Klose, P. Ferrero, J. Greiner, L.A. Arnold, E. Gonsalves, D.H. Hartmann, Adria Updike, D.A. Kann, T. Krühler, E. Palazzi, S. Savaglio, S. Schulze, P.M.J. Afonso, L. Amati, A.J. Castro-Tirado, C. Clemens, R. Filgas, J. Gorosabel, L.K. Hunt, A. Küpcü Yoldas, N. Masetti, M. Nardini, A. Nicuesa Guelbenzu, F.E. Olivares, E. Pian, A. Rau, P. Schady, S. Schmidl, A. Yoldas, A. De Ugarte Postigo

Arts & Sciences Faculty Publications

No abstract provided.

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Supersolar Metal Abundances In Two Galaxies At Z ∼ 3.57 Revealed By The Grb 090323 Afterglow Spectrum, S. Savaglio, A. Rau, J. Greiner, T. Kruhler, S. Mcbreen, D.H. Hartmann, Adria Updike, R. Filgas, S. Klose, P. Afonso, C. Clemens, A. Kupcu Yoldas, F. Olivares E., V. Sudilovsky, G. Szokoly Jan 2012

Supersolar Metal Abundances In Two Galaxies At Z ∼ 3.57 Revealed By The Grb 090323 Afterglow Spectrum, S. Savaglio, A. Rau, J. Greiner, T. Kruhler, S. Mcbreen, D.H. Hartmann, Adria Updike, R. Filgas, S. Klose, P. Afonso, C. Clemens, A. Kupcu Yoldas, F. Olivares E., V. Sudilovsky, G. Szokoly

Arts & Sciences Faculty Publications

No abstract provided.

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Comparative Study Of High-Order Positivity-Preserving Weno Schemes, D. V. Kotov, Helen C. Yee, Bjorn Sjögreen Jan 2012

Comparative Study Of High-Order Positivity-Preserving Weno Schemes, D. V. Kotov, Helen C. Yee, Bjorn Sjögreen

United States National Aeronautics and Space Administration: Publications

In gas dynamics and magnetohydrodynamics flows, physically, the density ρ and the pressure p should both be positive. In a standard conservative numerical scheme, however, the computed internal energy is obtained by subtracting the kinetic energy from the total energy, resulting in a computed p that may be negative. Examples are problems in which the dominant energy is kinetic. Negative ρ may often emerge in computing blast waves. In such situations the computed eigenvalues of the Jacobian will become imaginary. Consequently, the initial value problem for the linearized system will be ill posed. This explains why failure of preserving positivity …

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Controlling Calibration Errors In Gravitational-Wave Detectors By Precise Location Of Calibration Forces, Hernan P. Daveloza, M Afrin Badhan, Mario C. Diaz, K. Kawabe, P. N. Konverski, M. Landry, R. L. Savage Jan 2012

Controlling Calibration Errors In Gravitational-Wave Detectors By Precise Location Of Calibration Forces, Hernan P. Daveloza, M Afrin Badhan, Mario C. Diaz, K. Kawabe, P. N. Konverski, M. Landry, R. L. Savage

Physics & Astronomy Faculty Publications

We present results of finite element analysis simulations which could lead to more accurate calibration of interferometric gravitational wave detectors. Calibration and actuation forces applied to the interferometer test masses cause elastic deformation, inducing errors in the calibration. These errors increase with actuation frequency, and can be greater than 50% at frequencies above a few kilohertz. We show that they can be reduced significantly by optimizing the position at which the forces are applied. The Advanced LIGO [1] photon calibrators use a two-beam configuration to reduce the impact of local deformations of the test mass surface. The position of the …

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On The Synthesis And Physical Properties Of Iron Doped Sno2 Nanoparticles, X. Wei, R. Georgescu, N. Ali, I. Morjan, T. A. George, F. Dumitrache, R. Birjega, Mircea Chipara Jan 2012

On The Synthesis And Physical Properties Of Iron Doped Sno2 Nanoparticles, X. Wei, R. Georgescu, N. Ali, I. Morjan, T. A. George, F. Dumitrache, R. Birjega, Mircea Chipara

Physics & Astronomy Faculty Publications

The synthesis of iron doped tin oxide by pulsed laser pyrolysis is reported. The as obtained nanoparticles have a dominant SnO2 phase (as revealed by Wide Angle X-ray Scattering), with particles of the order of 10 nm. The doping with iron or iron oxide triggers magnetic properties as confirmed by SQUID experiments. EDX measurements supported the presence of Fe while Wide Angle X-ray Scattering failed to sense any iron or iron-oxide phase. It is concluded that Fe is well dispersed within the tin-oxide nanoparticles. The coercitive field has a complex dependence on the Fe/Sn content suggesting that the magnetization is …

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High-Speed Acousto-Optic Shutter With No Optical Frequency Shift, W J. Schwenger, James M. Higbie Jan 2012

High-Speed Acousto-Optic Shutter With No Optical Frequency Shift, W J. Schwenger, James M. Higbie

Faculty Journal Articles

Acousto-optic modulators are widely used for rapid switching and shuttering of laser beams. In many applications, the concomitant frequency shift is undesirable and must be compensated for elsewhere in the system. Here we present a simple method of achieving rapid laser power switching without an accompanying laser frequency shift. The demonstrated acousto-optic shutter achieves a switching time of around 25 ns, an extinction ratio of 46 dB, and efficiency comparable to a conventional double-pass acousto-optical modulator configuration. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746292]

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Phase Estimation With Two-Mode Squeezed Vacuum And Parity Detection: Bayesian Analysis, Keith Motes Jan 2012

Phase Estimation With Two-Mode Squeezed Vacuum And Parity Detection: Bayesian Analysis, Keith Motes

Honors Capstones

No abstract provided.

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Detecting And Characterizing Exoplanets: The Gj 436 And Hd 149026 Systems, Kevin Stevenson Jan 2012

Detecting And Characterizing Exoplanets: The Gj 436 And Hd 149026 Systems, Kevin Stevenson

Electronic Theses and Dissertations

This dissertation investigates two stellar systems known to contain extrasolar planets. It is comprised of five chapters that are readily divided into three independent but related analyses. Chapter 1 reports on the analysis of low signal-to-noise secondary-eclipse observations of the Neptune-sized exoplanet GJ 436b using the Spitzer Space Telescope in multiple infrared channels. The measured wavelength-dependent eclipse depths provide constraints on the planet’s dayside atmospheric composition and thermal profile. The analysis indicates that GJ 436b’s atmosphere is abundant in carbon monoxide and deficient in methane relative to thermochemical equilibrium models for the predicted hydrogen-dominated atmosphere. Chapter 2 discusses the techniques …

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