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Astrophysics and Astronomy

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2004

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Articles 1 - 30 of 159

Full-Text Articles in Physical Sciences and Mathematics

Evidence For Correlated Titanium And Deuterium Depletion In The Galactic Ism, Jason X. Prochaska, Todd M. Tripp, Christopher Howk Dec 2004

Evidence For Correlated Titanium And Deuterium Depletion In The Galactic Ism, Jason X. Prochaska, Todd M. Tripp, Christopher Howk

Todd M. Tripp

Current measurements indicate that the deuterium abundance in diffuse interstellar gas varies spatially by a factor of ~4 among sightlines extending beyond the Local Bubble. One plausible explanation for the scatter is the variable depletion of D onto dust grains. To test this scenario, we have obtained high signal-to-noise, high resolution profiles of the refractory ion Ti II along seven Galactic sightlines with D/H ranging from 0.65 to 2.1 × 10−5. These measurements, acquired with the recently upgraded Keck/HIRES spectrometer, indicate a correlation between Ti/H and D/H at the > 95% c.l. Therefore, our observations support the interpretation that D/H scatter …

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Evidence For Correlated Titanium And Deuterium Depletion In The Galactic Ism, Jason X. Prochaska, Todd M. Tripp, Christopher Howk Dec 2004

Evidence For Correlated Titanium And Deuterium Depletion In The Galactic Ism, Jason X. Prochaska, Todd M. Tripp, Christopher Howk

Astronomy Department Faculty Publication Series

Current measurements indicate that the deuterium abundance in diffuse interstellar gas varies spatially by a factor of ~4 among sightlines extending beyond the Local Bubble. One plausible explanation for the scatter is the variable depletion of D onto dust grains. To test this scenario, we have obtained high signal-to-noise, high resolution profiles of the refractory ion Ti II along seven Galactic sightlines with D/H ranging from 0.65 to 2.1 × 10−5. These measurements, acquired with the recently upgraded Keck/HIRES spectrometer, indicate a correlation between Ti/H and D/H at the > 95% c.l. Therefore, our observations support the interpretation that D/H scatter …

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Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner Dec 2004

Structural Properties Of Discs And Bulges Of Early-Type Galaxies, Roelof S. De Jong, Luc Simard, Roger L. Davies, R. P. Saglia, David Burstein, Matthew Colless, Robert Mcmahan, Gary Wegner

Dartmouth Scholarship

We have used the EFAR sample of galaxies to investigate the light distributions of early-type galaxies. We decompose the two-dimensional light distribution of the galaxies in a flattened spheroidal component with a Sérsic radial light profile and an inclined disc component with an exponential light profile. We show that if we assume that all galaxies can have a spheroidal and a disc component, then the brightest, bulge-dominated elliptical galaxies have a fairly broad distribution in the Sérsic profile shape parameter nB, with a median of approximately 3.7 and with σ∼ 0.9. Other galaxies have smaller nB values. …

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Signature Of Electron Capture In Iron‐Rich Ejecta Of Sn 2003du, Peter Hoflich, Christopher L. Gerardy, Ken-Ichi Nomoto, Kentaro Motohara, Robert A. Fesen Dec 2004

Signature Of Electron Capture In Iron‐Rich Ejecta Of Sn 2003du, Peter Hoflich, Christopher L. Gerardy, Ken-Ichi Nomoto, Kentaro Motohara, Robert A. Fesen

Dartmouth Scholarship

Late-time near-infrared and optical spectra of the normal-bright Type Ia supernova 2003du about 300 days after the explosion are presented. At this late epoch, the emission profiles of well-isolated [Fe II] lines (in particular that of the strong 1.644 μm feature) trace out the global kinematic distribution of radioactive material in the expanding supernova ejecta. In SN 2003du, the 1.644 μm [Fe II] line seems to show a flat-topped profile, indicative of a thick but hollow-centered expanding shell, rather than a strongly peaked profile that would be expected from a "center-filled" distribution. Based on detailed models for exploding Chandrasekhar-mass white …

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A Neptune-Mass Planet Orbiting The Nearby M Dwarf Gj 436, R. Paul Butler, Steve S. Vogt, Geoffrey W. Marcy, Debra A. Fischer, Jason T. Wright, Gregory W. Henry, Gregory Laughlin, Jack J. Lissauer Dec 2004

A Neptune-Mass Planet Orbiting The Nearby M Dwarf Gj 436, R. Paul Butler, Steve S. Vogt, Geoffrey W. Marcy, Debra A. Fischer, Jason T. Wright, Gregory W. Henry, Gregory Laughlin, Jack J. Lissauer

Information Systems and Engineering Management Research Publications

We report precise Doppler measurements of GJ 436 (M2.5 V) obtained at Keck Observatory. The velocities reveal a planetary companion with orbital period of 2.644 days, eccentricity of 0.12 (consistent with zero), and velocity semiamplitude of K = 18.1 m s-1. The minimum mass (M sin i) for the planet is 0.067MJup = 1.2MNep = 21MEarth, making it the lowest mass exoplanet yet found around a main-sequence star and the first candidate in the Neptune-mass domain. GJ 436 (mass = 0.41 M☉) is only the second M dwarf found to harbor a planet, joining the two-planet system around GJ 876. …

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The Initial-Final Mass Relationship: Spectroscopy Of White Dwarfs In Ngc 2099 (M37), Jasonjot Singh Kalirai, Ted Von Hippel, Et Al. Dec 2004

The Initial-Final Mass Relationship: Spectroscopy Of White Dwarfs In Ngc 2099 (M37), Jasonjot Singh Kalirai, Ted Von Hippel, Et Al.

Publications

We present new observations of very faint white dwarfs (WDs) in the rich open star cluster NGC 2099 (M37). Following deep, wide-field imaging of the cluster using the Canada-France-Hawaii Telescope, we have now obtained spectroscopic observations of candidate WDs using both the Gemini Multi-Object Spectrograph on Gemini North and the Low-Resolution Imaging Spectrometer on Keck. Of our 24 WD candidates (all fainter than V = 22.4), 21 are spectroscopically confirmed to be bona fide WDs, four or five of which are most likely field objects. Fitting 18 of the 21 WD spectra with model atmospheres, we find that most WDs …

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Atomic Force Microscope Conductivity Measurements Of Single Ferritin Molecules, Degao Xu Dec 2004

Atomic Force Microscope Conductivity Measurements Of Single Ferritin Molecules, Degao Xu

Theses and Dissertations

Conductive Atomic Force Microscope (c-AFM) was used to measure the conductivity of single horse spleen ferritin (HoSF) and azotobacter vinelandii bacterial ferritin (AvBF) molecules deposited on flat gold surfaces. A 500 micron diameter gold ball was also used as a contact probe to measure the conductivity of a thin film of ferritin molecules. The average current measured for holo HoSF was 13 and 5 times larger than that measured for apo HoSF as measured by c-AFM at 1V and gold ball at 2V and respectively, which indicates that the core of ferritin is more conductive than the protein shell and …

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Self‐Consistent Diffusive Lifetimes Of Weibel Magnetic Fields In Gamma‐Ray Bursts, C. H. Jaroschek, H. Lesch, R. A. Treumann Dec 2004

Self‐Consistent Diffusive Lifetimes Of Weibel Magnetic Fields In Gamma‐Ray Bursts, C. H. Jaroschek, H. Lesch, R. A. Treumann

Dartmouth Scholarship

Weibel filamentation in relativistic plasma shell collisions has been demonstrated as an efficient and fast mechanism for the generation of near-equipartition magnetic fields in self-consistent particle-in-cell (PIC) simulations. In generic γ-ray burst (GRB) models with kinetically dominated plasma outflow, sufficient strength and lifetime of magnetic fields are essential to validate synchrotron emission as the source of radiative outbursts. In this article we report on self-consistent PIC simulations of pair-plasma shell collisions in the highly relativistic regime with particle ensembles up to 5 × 108. Energy dependence of magnetic field generation in the Weibel process is discussed, and for …

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Discovery Of The Near-Ir Afterglow And Of The Host Of Grb 030528, A. Rau, J. Greiner, S. Klose, M. Salvato, J. M. Castro Cerón, Dieter H. Hartmann, A. Fruchter, A. Levan, N. R. Tanvir, J. Gorosabel Dec 2004

Discovery Of The Near-Ir Afterglow And Of The Host Of Grb 030528, A. Rau, J. Greiner, S. Klose, M. Salvato, J. M. Castro Cerón, Dieter H. Hartmann, A. Fruchter, A. Levan, N. R. Tanvir, J. Gorosabel

Publications

The rapid dissemination of an arcmin-sized HETE-2 localization of the long-duration X-ray flash GRB 030528 led to a ground-based multi-observatory follow-up campaign. We report the discovery of the near-IR afterglow, and also describe the detection of the underlying host galaxy in the optical and near-IR bands. The afterglow is classified as “optically dark” as it was not detected in the optical band. The K-band photometry presented here suggests that the lack of optical detection was simply the result of observational limitations (lack of rapid and deep observations plus high foreground extinction). Simple power law fits to the afterglow in the …

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Discovery Of Co Gas In The Inner Disk Of Tw Hydrae, Terrence W. Rettig, Joe Haywood, Theodore Simon, Sean D. Brittain, Erika Gibb Dec 2004

Discovery Of Co Gas In The Inner Disk Of Tw Hydrae, Terrence W. Rettig, Joe Haywood, Theodore Simon, Sean D. Brittain, Erika Gibb

Publications

We report the detection of rovibrationally excited CO emission from the inner disk of the classical T Tauri star (cTTS) TW Hya. We observe ~6 × 1021 g of CO gas with a rotational temperature of 430 ± 40 K. The linearity of the excitation plot suggests that the CO is optically thin. Atypical for cTTSs, hot CO was not detected, implying that TW Hya has cleared its inner disk region out to a radial distance of ~0.5 AU. We discuss implications for the structure of the disk as it relates to replenishment and planet formation.

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Coordinate Conditions For A Uniformly Accelerated Or Static Plane Symmetric Metric, Preston Jones, Lucas Wanex Dec 2004

Coordinate Conditions For A Uniformly Accelerated Or Static Plane Symmetric Metric, Preston Jones, Lucas Wanex

Publications

The coordinate conditions for three exact solutions for the metric components of a coordinate system with constant acceleration or of a static plane symmetric gravitational field are presented. First, the coordinate condition that the acceleration of light is constant is applied to the field equations to derive the metric of a coordinate system of constant acceleration. Second, the coordinate conditions required to produce the metrics of Rindler and Lass are applied to the field equations to calculate the components of these two metrics and the coordinate velocities and coordinate accelerations for light of these two metrics are compared to the …

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The O Vi Absorbers Toward Pg 0953+415: High-Metallicity, Cosmic-Web Gas Far From Luminous Galaxies, Todd M. Tripp, Bastien Aracil, David V. Bowen, Edward B. Jenkins Nov 2004

The O Vi Absorbers Toward Pg 0953+415: High-Metallicity, Cosmic-Web Gas Far From Luminous Galaxies, Todd M. Tripp, Bastien Aracil, David V. Bowen, Edward B. Jenkins

Todd M. Tripp

The spectrum of the low-redshift QSO PG0953+415 shows two strong, intervening O VI absorption systems. To study the nature of these absorbers, we have used the Gemini Multiobject Spectrograph to conduct a deep spectroscopic galaxy redshift survey in the 5' x 5' field centered on the QSO. This survey is fully complete for r' < 19.7 and is 73% complete for r' < 21.0. We find three galaxies at the redshift of the higher-z O VI system (z = 0.14232) including a galaxy at projected distance rho = 155 kpc. We find no galaxies in the Gemini field at the redshift of the lower-z O VI absorber (z = 0.06807), which indicates that the nearest galaxy is more than 195 kpc away or has L < 0.04 L*. Previous shallower surveys covering a larger field have shown that the z = 0.06807 O VI absorber is affiliated with a group/filament of galaxies, but the nearest known galaxy has rho = 736 kpc. The z = 0.06807 absorber is notable for several reasons. The absorption profiles reveal simple kinematics indicative of quiescent material. The H I line widths and good alignment of the H I and metal lines favor photoionization and, moreover, the column density ratios imply a high metallicity: [M/H] = -0.3 +/- 0.12. The z = 0.14232 O VI system is more complex and less constrained but also indicates a relatively high metallicity. Using galaxy redshifts from SDSS, we show that both of the PG0953+415 O VI absorbers are located in large-scale filaments of the cosmic web. Evidently, some regions of the web filaments are highly metal enriched. We discuss the origin of the high-metallicity gas and suggest that the enrichment might have occurred long ago (at high z).

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Nonlinear Parallel And Perpendicular Diffusion Of Charged Cosmic Rays In Weak Turbulence, Andreas Schalchi, John William Bieber, William H. Matthaeus, Gang Qin Nov 2004

Nonlinear Parallel And Perpendicular Diffusion Of Charged Cosmic Rays In Weak Turbulence, Andreas Schalchi, John William Bieber, William H. Matthaeus, Gang Qin

Aerospace, Physics, and Space Science Faculty Publications

The problem of particle transport perpendicular to a magnetic background field is well known in cosmic-ray astrophysics. Whereas it is widely accepted that quasi-linear theory (QLT) of particle transport does not provide the correct results for perpendicular diffusion, it was assumed for a long time that QLT is the correct theory for parallel diffusion. In the current paper we demonstrate that QLT is in general also incorrect for parallel particle transport if we consider composite turbulence geometry. Motivated through the recent success of the so-called nonlinear guiding center theory of perpendicular diffusion, we present a new theory for parallel and …

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A Million Secondchandraview Of Cassiopeia A, Una Hwang, J. Martin Laming, Carles Badenes, Fred Berendse, John Blondin, Denis Cioffi, Tracey Delaney, Daniel Dewey, Robert Fesen Nov 2004

A Million Secondchandraview Of Cassiopeia A, Una Hwang, J. Martin Laming, Carles Badenes, Fred Berendse, John Blondin, Denis Cioffi, Tracey Delaney, Daniel Dewey, Robert Fesen

Dartmouth Scholarship

We introduce a million second observation of the supernova remnant Cassiopeia A with the Chandra X-Ray Observatory. The bipolar structure of the Si-rich ejecta (northeast jet and southwest counterpart) is clearly evident in the new images, and their chemical similarity is confirmed by their spectra. These are most likely due to jets of ejecta as opposed to cavities in the circumstellar medium, since we can reject simple models for the latter. The properties of these jets and the Fe-rich ejecta will provide clues to the explosion of Cas A.

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The Origin Of Fe Ii Emission In Active Galactic Nuclei, J. A. Baldwin, Gary J. Ferland, K. T. Korista, F. Hamann, A. Lacluyzé Nov 2004

The Origin Of Fe Ii Emission In Active Galactic Nuclei, J. A. Baldwin, Gary J. Ferland, K. T. Korista, F. Hamann, A. Lacluyzé

Physics and Astronomy Faculty Publications

We used a very large set of models of broad emission line region (BELR) clouds in active galactic nuclei to investigate the formation of the observed Fe II emission lines. We show that photoionized BELR clouds cannot produce both the observed shape and observed equivalent width of the 2200-2800 Å Fe II UV bump unless there is considerable velocity structure corresponding to a microturbulent velocity parameter vturb≥100 km s-1 for the locally optimally emitting cloud models used here. This could be either microturbulence in gas that is confined by some phenomenon such as MHD waves or a …

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Geometric Acoustic Modeling Of The Lds Conference Center, Heather Smith Nov 2004

Geometric Acoustic Modeling Of The Lds Conference Center, Heather Smith

Theses and Dissertations

This thesis discusses the process of modeling a 21,000 seat fan-shaped auditorium using methods of geometric acoustics. Two commercial geometric acoustics software packages were used in the research: CATT-Acoustic™ 8.0 and EASE™ 4.1. The process first included creating preliminary models of the hall using published absorption coefficients for its surfaces and approximate scattering coefficients based on current best-known techniques. A detailed analysis determined the minimum numbers of rays needed in both packages to produce reliable results with these coefficient values. It was found that 100,000 rays were needed for CATT™ and 500,000 rays were needed for EASE™. Analysis was also …

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Geocoronal Hydrogen Studies Using Fabry-Perot Interferometers, S. M. Nossal, E. J. Mierkiewicz, F. L. Roesler, J. Bishop, R. J. Reynolds Nov 2004

Geocoronal Hydrogen Studies Using Fabry-Perot Interferometers, S. M. Nossal, E. J. Mierkiewicz, F. L. Roesler, J. Bishop, R. J. Reynolds

Publications

Ground based Fabry-Perot observations of solar excited geocoronal hydrogen fluorescence emissions are one of the primary means of studying the neutral upper atmosphere [Atreya et al., 1975; Meriwether et al., 1980; Yelle and Roesler, 1985; Shih et al., 1985; Kerr et al., 2001a,b; He et al., 1993; Nossal et al., 1993, 1998, 2004; Bishop et al., 2001; Mierkiewicz, 2002; and references therein]. Excellent reviews of early ground-based geocoronal Balmer α observations are found in: Krassovsky et al. [1966], Krassovsky [1971], Donahue [1964, 1966], Tinsley [1974], Fahr and Shizgal [1983] and Kerr et al. [2001a]. Instruments onboard satellites and rockets also …

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Probing A Grb Progenitor At A Redshift Of Z=2: A Comprehensive Observing Campaign Of The Afterglow Of Grb 030226, S. Klose, J. Greiner, A. Rau, A. A. Henden, Dieter H. Hartmann, A. Zeh, C. Reis, N. Masetti, D. Malesani, E. Guenther Nov 2004

Probing A Grb Progenitor At A Redshift Of Z=2: A Comprehensive Observing Campaign Of The Afterglow Of Grb 030226, S. Klose, J. Greiner, A. Rau, A. A. Henden, Dieter H. Hartmann, A. Zeh, C. Reis, N. Masetti, D. Malesani, E. Guenther

Publications

We report results from a comprehensive follow-up observing campaign of the afterglow of GRB 030226, in-cluding VLTspectroscopy, VLT polarimetry, and Chandra X-ray observations. In addition, we present BOOTES-1 wide-field observations at the time of the occurrence of the burst. First observations at ESO started 0.2 days after the event when the gamma ray burst (GRB) afterglow was at a magnitude of R $19 and continued until the afterglow had faded below the detection threshold (R > 26). No underlying host galaxy was found. The optical light curve shows a break around 0.8 days after the burst, which is achromatic within the …

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The White Dwarf Luminosity Function: The Shape Of Things To Come, Ted Von Hippel, M. Kilie, J. Munn, K. Williams, J. Libert, D. E. Winget, T. S. Metcalfe, Et Al. Oct 2004

The White Dwarf Luminosity Function: The Shape Of Things To Come, Ted Von Hippel, M. Kilie, J. Munn, K. Williams, J. Libert, D. E. Winget, T. S. Metcalfe, Et Al.

Publications

We describe a new survey for cool white dwarfs that supplements Sloan Digital Sky Survey photometry with USNO proper motions and followup spectroscopy. To date we have discovered and spectroscopically confirmed 80 new moderate temperature and cool white dwarfs. We have also found a handful of high-velocity white dwarfs and we expect a sizable fraction of these to be thick disk or possibly halo objects. Our survey is designed to find 104 new white dwarfs, although only 60 will be among the faintest white dwarfs (MV 16), where most of the age-sensitivity resides. We discuss an extension of our survey …

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Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer Oct 2004

Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

The m = 1 diocotron mode in non-neutral plasmas has long been thought of as a shifted equilibrium, and its frequency has been approximately calculated in this way by Fine and Driscoll [Phys. Plasmas 5, 601 (1998)]. This article shows that this idea can be coupled with a standard axisymmetric equilibrium calculation on a grid to calculate the frequency of this mode to very high precision including both finite-length and thermal effects, provided that the Debye length is small enough. As the Debye length begins to approach the plasma size not only does the shifted equilibrium calculation fail to predict …

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Location Of The Optical Reverse Shock In The Cassiopeia A Supernova Remnant, Jon A. Morse, Robert A. Fesen, Roger A. Chevalier, Kazimierz J. Borkowski Oct 2004

Location Of The Optical Reverse Shock In The Cassiopeia A Supernova Remnant, Jon A. Morse, Robert A. Fesen, Roger A. Chevalier, Kazimierz J. Borkowski

Dartmouth Scholarship

We use two epochs of Hubble Space Telescope WFPC2 images separated by 2 yr to determine the location and propagation of the reverse shock (RS) in the young supernova remnant Cassiopeia A (Cas A). The images trace optical line emission from fast-moving knots and filaments of highly processed ejecta as they cross the RS, become heated and compressed, and radiatively cool. At numerous positions around the optical shell, new emission features are seen in the 2002 images that were not yet visible in the 2000 exposures. In a few instances emission features seen in the first epoch have completely disappeared …

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Optical Properties And Application Of Uranium-Based Thin Films For The Extreme Ultraviolet And Soft X-Ray Region, Richard L. Sandberg, David D. Allred, Shannon Lunt, Marie K. Urry, R. Steven Turley Oct 2004

Optical Properties And Application Of Uranium-Based Thin Films For The Extreme Ultraviolet And Soft X-Ray Region, Richard L. Sandberg, David D. Allred, Shannon Lunt, Marie K. Urry, R. Steven Turley

Faculty Publications

Uranium oxide and uranium nitride thin films reflect significantly more than all previously known/standard reflectors (e.g., nickel, gold, and iridium) for most of the 4-10 nm range at low angles of incidence. This work includes measurements of the EUV/soft x-ray (2-20 nm) reflectance of uranium-based thin films (~20 nm thick) and extraction of their optical constants (d and ?). We report the reflectances at 5, 10, and 15 degrees grazing incidence of air-oxidized sputtered uranium, reactively sputtered (O2) uranium oxide, and reactively sputtered (N2) uranium nitride thin films measured at Beamline 6.3.2 at the Advanced Light Source (ALS) at Lawrence …

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Spectroscopic Orbits Of Potential Interferometric Binaries, Francis C. Fekel, Jocelyn Tomkin Oct 2004

Spectroscopic Orbits Of Potential Interferometric Binaries, Francis C. Fekel, Jocelyn Tomkin

Information Systems and Engineering Management Research Publications

We are obtaining high-resolution, red-wavelength spectra at McDonald and Kitt Peak National Observatory to improve the orbits of known spectroscopic binaries that are potential targets for ground-based optical interferometers. The combination of such observations will produce three-dimensional orbits from which very accurate masses and orbital parallaxes can be obtained for double-lined systems. This spectroscopic program will be expanded and placed on the menu of the 2 meter Automatic Spectroscopic Telescope of Tennessee State University once it commences routine operation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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Managing The Operations Of The Tsu 2-M Automatic Spectroscopic Telescope, Joel A. Eaton, Michael Williamson Oct 2004

Managing The Operations Of The Tsu 2-M Automatic Spectroscopic Telescope, Joel A. Eaton, Michael Williamson

Information Systems and Engineering Management Research Publications

Tennessee State University has built and is now operating a completely automatic 2-m telescope for highdispersion spectroscopy. This system consists of an alt-azimuth f/8 Cassegrain telescope, housed in an enclosure with a roll-off roof, coupled to a white-pupil echelle spectrograph through a fiber-optic cable. We discuss managing this facility over the Internet with emphasis on 1) the configuration of the control system, 2) logging, 3) troubleshooting and quality control, 4) updating the target lists, and 5) archiving and handling the data.

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Mega: The Next Generation Medium Energy Gamma-Ray Telescope, James M. Ryan, R Andritsche, Peter F. Bloser, J Cravens, M L. Cherry, G Dicocco, T G. Guzik, Dieter H. Hartman, Stanley D. Hunter, G Kanbach, R M. Kippen, J Kurfess, John R. Macri, Mark L. Mcconnell, R S. Miller, W Paciesas, B F. Phlips, V Reglero, J G. Stacy, Mark Strickman, W T. Vestrand, J P. Wefel, Eric Wulf, A Zoglauer, Allen Zych Oct 2004

Mega: The Next Generation Medium Energy Gamma-Ray Telescope, James M. Ryan, R Andritsche, Peter F. Bloser, J Cravens, M L. Cherry, G Dicocco, T G. Guzik, Dieter H. Hartman, Stanley D. Hunter, G Kanbach, R M. Kippen, J Kurfess, John R. Macri, Mark L. Mcconnell, R S. Miller, W Paciesas, B F. Phlips, V Reglero, J G. Stacy, Mark Strickman, W T. Vestrand, J P. Wefel, Eric Wulf, A Zoglauer, Allen Zych

Space Science Center

The MEGA mission would enable a sensitive all-sky survey of the medium-energy ?-ray sky (0.3-50 MeV). This mission will bridge the huge sensitivity gap between the COMPTEL and OSSE experiments on the Compton Gamma Ray Observatory, the SPI and IBIS instruments on INTEGRAL and the visionary ACT mission. It will, among other things, serve to compile a much larger catalog of sources in this energy range, perform far deeper searches for supernovae, better measure the galactic continuum emission as well as identify the components of the cosmic diffuse emission. The large field of view will allow MEGA to continuously monitor …

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Caster: A Scintillator-Based Black Hole Finder Probe, Mark L. Mcconnell, M L. Cherry, T G. Guzik, R M. Kippen, James M. Ryan, John R. Macri, R S. Miller, W Paciesas, B Schaefer, J G. Stacy, J P. Wefel, W T. Vestrand Oct 2004

Caster: A Scintillator-Based Black Hole Finder Probe, Mark L. Mcconnell, M L. Cherry, T G. Guzik, R M. Kippen, James M. Ryan, John R. Macri, R S. Miller, W Paciesas, B Schaefer, J G. Stacy, J P. Wefel, W T. Vestrand

Space Science Center

The primary scientific mission of the Black Hole Finder Probe (BHFP), part of the NASA Beyond Einstein program, is to survey the local Universe for black holes over a wide range of mass and accretion rate. One approach to such a survey is a hard X-ray coded-aperture imaging mission operating in the 10-600 keV energy band, a spectral range that is considered to be especially useful in the detection of black hole sources. The development of new inorganic scintillator materials provides improved performance (for example, with regards to energy resolution and timing) that is well suited to the BHFP science …

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Globular Cluster And Galaxy Formation: M31 The Milky Way And Implications For Globular Cluster Systems Of Spiral Galaxies, David Burstein, Yong Li, Kenneth C. Freeman, John E. Norris, Michael S. Bessell, Joss Bland-Hawthorn, Brad K. Gibson, Mlchael A. Beasley, Hyun Chul Lee, Beatriz Barbuy, John P. Huchra, Jean P. Brodif, Duncan A. Forbes Oct 2004

Globular Cluster And Galaxy Formation: M31 The Milky Way And Implications For Globular Cluster Systems Of Spiral Galaxies, David Burstein, Yong Li, Kenneth C. Freeman, John E. Norris, Michael S. Bessell, Joss Bland-Hawthorn, Brad K. Gibson, Mlchael A. Beasley, Hyun Chul Lee, Beatriz Barbuy, John P. Huchra, Jean P. Brodif, Duncan A. Forbes

Physics and Astronomy Faculty Publications and Presentations

We find that the globular cluster (GC) systems of the Milky Way and of our neighboring spiral galaxy, M31, comprise two distinct entities, differing in three respects. First, M31 has a set of young GCs, ranging in age from a few times 10 2 Myr to 5 Gyr old, as well as old GCs. No such very young GCs are known in the Milky Way. Second, we confirm that the oldest M31 GCs have much higher nitrogen abundances than do Galactic GCs at equivalent metallicities, while carbon abundances appear normal for the GCs in both galaxies. Third, Morrison and coworkers …

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Dark-Matter Electric And Magnetic Dipole Moments, Kris Sigurdson, Michael Doran, Andriy Kurylov, Robert R. Caldwell, Marc Kamionkowski Oct 2004

Dark-Matter Electric And Magnetic Dipole Moments, Kris Sigurdson, Michael Doran, Andriy Kurylov, Robert R. Caldwell, Marc Kamionkowski

Dartmouth Scholarship

We consider the consequences of a neutral dark-matter particle with a nonzero electric and/or magnetic dipole moment. Theoretical constraints, as well as constraints from direct searches, precision tests of the standard-model, the cosmic microwave background and matter power spectra, and cosmic gamma rays, are included. We find that a relatively light particle with mass between an MeV and a few GeV and an electric or magnetic dipole as large as ∼3×10−16e  cm (roughly 1.6×10−5μB) satisfies all experimental and observational bounds. Some of the remaining parameter space may be probed with forthcoming more sensitive direct searches and with the Gamma-Ray Large …

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Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey Oct 2004

Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey

Theses and Dissertations

Traditional methods for the investigation of sound fields generally rely on a microphone to convert sound pressure into an electrical signal which can be recorded, displayed, and so forth. The squared sound pressure is directly related to potential energy density. Consequently, the measurement of sound pressure alone does not inherently provide insight into the total energy density of the sound field. Specifically, no information about the kinetic energy density of the sound field is available from this measurement alone. However, it is possible to use two microphones to estimate particle velocity. The squared particle velocity magnitude is directly related to …

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Cross Sections Fall 2004, Department Of Physics And Astronomy Oct 2004

Cross Sections Fall 2004, Department Of Physics And Astronomy

Cross Sections

No abstract provided.

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