Physical Sciences and Mathematics Commons^™

Further Investigation Of The Time Delay, Magnification Ratios, And Variability In The Gravitational Lens 0218 + 357, A. S. Cohen, J. N. Hewitt, C. B. Moore, Deborah B. Haarsma

University Faculty Publications and Creative Works

High-precision VLA flux density measurements for the lensed images of 0218 + 357 yield a time delay of 10.1 +1.5-1.6 days (95% confidence). This is consistent with independent measurements carried out at the same epoch by Biggs and colleagues in 1999, lending confidence to the robustness of the time delay measurement. However, since both measurements make use of the same features in the light curves, it is possible that the effects of unmodeled processes, such as scintillation or microlensing, are biasing both time delay measurements in the same way. Our time delay estimates result in confidence intervals that are somewhat …

Detection Of Variable Frequency Signals Using A Fast Chirp Transform, F. A. Jenet, T. A. Prince

Physics and Astronomy Faculty Publications and Presentations

The detection of signals with varying frequency is important in many areas of physics and astrophysics. The current work was motivated by a desire to detect gravitational waves from the binary inspirai of neutron stars and black holes, a topic of significant interest for the new generation of interferometric gravitational wave detectors such as LIGO. However, this work has significant generality beyond gravitational wave signal detection. We define a fast chirp transform (FCT) analogous to the fast Fourier transform. Use of the FCT provides a simple and powerful formalism for detection of signals with variable frequency just as Fourier transform …

Faint Radio Sources And Star Formation History, Deborah B. Haarsma, R. B. Partridge, R. A. Windhorst, E. A. Richards

University Faculty Publications and Creative Works

The centimeter-wave luminosity of local radio galaxies correlates well with their star formation rate. We extend this correlation to surveys of high-redshift radio sources to estimate the global star formation history. The star formation rate found from radio observations needs no correction for dust obscuration, unlike the values calculated from optical and ultraviolet data. Three deep radio surveys have provided catalogs of sources with nearly complete optical identifications and nearly 60% complete spectroscopic redshifts: the Hubble Deep Field and Flanking Fields at 12h + 62°, the SSA13 field at 13h + 42°, and the V15 field at 14h + 52°. …

A Desktop Universe For The Introductory Astronomy Laboratory, Laurence A. Marschall, Glenn A. Snyder, Paul Richard Cooper

Physics and Astronomy Faculty Publications

What is a well-intentioned astronomy instructor to do? There is no argument that experience with the real world is desirable in any astronomy course, especially the introductory classes that fulfill the science distribution requirements at many colleges and universities. Though it is a simple matter to take students out of doors, show them the motions of the Sun, Moon, and stars, and have them squint for a few seconds at Saturn's rings through a telescope, these activities represent only a small portion of the subject matter of modern astronomy. It is simply not possible, given the constraints of time, weather, …

The Relative Age Of The Thin And Thick Galactic Disks, Wilson M. Liu, Brian Chaboyer

Dartmouth Scholarship

We determine the relative ages of the open cluster NGC 188 and selected Hipparcos field stars by isochrone fitting and compare them to the age of the thick-disk globular cluster 47 Tuc. The best-fit age for NGC 188 was determined to be 6.5 ± 1.0 Gyr. The solar-metallicity Hipparcos field stars yielded a slightly older thin-disk age, 7.5 ± 0.7 Gyr. Two slightly metal-poor ([Fe/H] = -0.22) field stars whose kinematic and orbital parameters indicate that they are members of the thin disk were found to have an age of 9.7 ± 0.6 Gyr. The age for 47 Tuc was …

Infrared Spectroscopy Of Symbiotic Stars. Ii. Orbits For Five S-Type Systems With Two-Year Periods, Francis C. Fekel, Kenneth H. Hinkle, Richard Joyce, Michael F. Skrutskie

Information Systems and Engineering Management Research Publications

Infrared radial velocities have been used to determine orbital elements for the cool giants of five well-known symbiotic systems, Z And, AG Dra, V443 Her, AX Per, and FG Ser, all of which have orbital periods near the two-year mean period for S-type symbiotics. The new orbits are in general agreement with previous orbits derived from optical velocities. From the combined optical and infrared velocities, improved orbital elements for the five systems have been determined. Each of the orbital periods has been determined solely from the radial-velocity data. The orbits are circular and have quite small mass functions of 0.001–0.03 …

Chromospherically Active Stars. Xviii. Sorting Out The Variability Of Hd 95559 And Gliese 410=Ds Leonis, Francis C. Fekel, Gregory W. Henry

Information Systems and Engineering Management Research Publications

We have obtained spectroscopy and photometry of HD 95559 and photometry of Gliese 410=DS Leonis. HD 95559 consists of a pair of essentially identical K1 V stars, whose orbital period we refine to 1.52599775+/-0.00000104 days. The system is photometrically variable with a mean period of 1.5264+/-0.0003 days. Despite minimum masses greater than 0.8 Msolar for each component, a search for eclipses proved negative. The lithium abundances of the components of HD 95559 indicate that the system is younger than the Hyades cluster, and its components may even have just arrived on the zero-age main sequence. Gl 410=DS Leo is also …

Development Of Realistic Simulations Of The Interactions Between Stars And The Interstellar Medium In Disk Galaxies, Thomas M. Zeltwanger

Electronic Theses and Dissertations

fWe have developed GALAXY, a two dimensional, self-consistent N-body plus hydro-dynamic computer program to model and study the behavior of disk galaxies like our Milky Way. Our goal is to better understand how such galaxies maintain their spiral structure for billions of years.

The program utilizes two independent gravitating N-body components. One simulates the collision-less star particles in the galaxy, and the other simulates colliding clouds. A gravitating hydrodynamic code simulates the interstellar medium. Additionally, a static spherical halo and a central black hole interact gravitationally with the other components of the model galaxy. All components interact with each other …

Three-Dimensional Imaging And Detection Efficiency Performance Of Orthogonal Coplanar Czt Strip Detectors, Mark L. Mcconnell, John R. Macri, James M. Ryan, K Larson, L A. Hamel, G Bernard, C Pomerleau, O Tousignant, Jean-Charles Leroux, V T. Jordanov

Space Science Center

We report on recent three-dimensional imaging performance and detection efficiency measurements obtained with 5 mm thick prototype CdZnTe detectors fabricated with orthogonal coplanar anode strips. In previous work, we have shown that detectors fabricated using this design achieve both very good energy resolution and sub-millimeter spatial resolution with fewer electronic channels than are required for pixel detectors. As electron-only devices, like pixel detectors, coplanar anode strip detectors can be fabricated in the thickness required to be effective imagers for photons with energies in excess of 500 keV. Unlike conventional double-sided strip detectors, the coplanar anode strip detectors require segmented contacts …

Analog Processing Of Signals From A Czt Strip Detector With Orthogonal Coplanar Anodes, K Larson, V T. Jordanov, Mark L. Mcconnell, John R. Macri, James M. Ryan, A Drake, L A. Hamel, O Tousignant

Space Science Center

We present the requirements, design, and performance of an analog circuit for processing the non-collecting anode strip signals from a cadmium zinc telluride (CZT) strip detector with orthogonal coplanar anodes. Detector signal simulations and measurements with a prototype are used to define the range of signal characteristics as a function of location of the gamma interaction in the detector. The signals from the non- collecting anode strip electrodes are used to define two of the three spatial coordinates including the depth of interaction, the z dimension. Analog signal processing options are discussed. A circuit to process the signals from the …

Hubble Space Telescope Imaging Spectrograph Observations Of The Hot White Dwarf In The Close Binary Feige 24, Stephane Vennes, Elisha F. Polomski, Thierry Lanz, John R. Thorstensen

Dartmouth Scholarship

We obtained and analyzed two Hubble Space Telescope Imaging Spectrograph spectra of the white dwarf in the DA plus dMe binary Feige 24. The spectra, obtained at orbital quadratures, provide new estimates of the white dwarf motion and gravitational redshift resulting in revised white dwarf parameters. An analysis of interstellar absorption lines reveals the presence of two clouds (+3.1 km s-1, +17.6 km s-1) in the line of sight toward Feige 24; one of these clouds (+17.6 km s-1) is identified with the "local cloud." A study of the Lyα H I and D I interstellar medium lines shows that …

Continuum Pumping Of [Fe Ii] In The Orion Nebula, E. M. Verner, D. A. Verner, J. A. Baldwin, Gary J. Ferland, P. G. Martin

Physics and Astronomy Faculty Publications

This paper presents detailed comparisons between numerical simulations of Fe II emission spectra and recent high-resolution and signal-to-noise spectra of the Orion Nebula. We have identified 40 [Fe II] lines in the spectrum, allowing extensive comparisons between theory and observations. The identifications are based on predictions of a realistic model of the Fe II atom, which includes the lowest 371 levels (all levels up to 11.6 eV). We investigate the dependence of the spectrum on electron density and on pumping by the stellar continuum. Orion is important because it provides a relatively simple environment in which to test complex simulations. …

Astrophysical Quantities Of Cepheid Variables Measured With The Navy Prototype Optical Interferometer, Tyler E. Nordgren, J. T. Armstrong, M. E. Germain, R. B. Hindsley, Arsen R. Hajian, Jeffrey J. Sudol, C. A. Hummel

Physics & Engineering Faculty Publications

No abstract provided.

The Infall Region Of Abell 576: Independent Mass And Light Profiles, Kenneth Rines, Margaret J. Geller, Antonaldo Diaferio, Joseph J. Mohr, Gary A. Wegner

Dartmouth Scholarship

We describe observations of the nearby (cz = 11,487 km s^-1) cluster of galaxies Abell 576 beyond the virial radius and into the infall region where galaxies are on their first or second pass through the cluster. Using 1057 redshifts, we use the infall pattern in redshift space to determine the mass profile of A576 to a radius of ~4 h^-1 Mpc. This mass estimation technique makes no assumptions about the equilibrium state of the cluster. Within ~1 h^-1 Mpc, the mass profile we derive exceeds that determined from X-ray observations by a factor of …

Numerical Simulations Of Steady And Pulsed Non-Adiabatic Magnetised Jets From Young Stars, Stephen O'Sullivan, Tom Ray

Articles

No abstract provided.

Book Review: 3-D Atlas Of Stars And Galaxies, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of 3-D Atlas of Stars and Galaxies by Richard Monkhouse and John Cox Springer, 2000. 95p, 1-85233-189-5 $42.00.

Resonance Line Scattering Polarization In Optically Thin Planar Equatorial Disks., Richard Ignace

Richard Ignace

This paper is the third in a series on the anisotropic scattering by optically thin resonance lines in extended stellar envelopes. Considered here is the polarization arising from resonance line scattering in equatorial disks. The shape of the polarized line profile is analytically derived under simplifying conditions of constant expansion or rotation for thin lines, with stellar occultation and finite star depolarization effects also included. The polarized profiles for the two cases are radically different. Moreover owing to the symmetries, rotation leads to profiles in both Q_ν and U_ν, whereas only a Q_ν profile survives for …

Metallic Nanoscale Fibers From Stable Iodine-Doped Carbon Nanotubes, Peter C. Eklund, Leonid Grigorian, Keith A. Williams, Gamini U. Sumanasekera, Shaoli Fang

Physics and Astronomy Faculty Patents

A method of doping involves soaking single-walled carbon nanotubes in molten iodine. Excess physisorbed iodine may then be removed by annealing.

The Two Micron All-Sky Survey: Removing The Infrared Foreground, John E. Gizis, Michael F. Skrutskie

Astronomy Department Faculty Publication Series

We introduce the properties of the Two Micron All-Sky Survey (2MASS) survey for IAU Symposium 204. 2MASS is a near-infrared survey of the entire sky characterized by high reliability and completeness. Catalogs and images for 47% of the sky are now available online. This data release has been used by Wright (2000) and Cambr´esy et al. (2000) to subtract the stellar foreground at 1.25 and 2.2 microns from COBE DIRBE data, revealing the cosmological near-infrared background.

Observational Constraints On The Internal Velocity Field Of Quasar Emission-Line Clouds, Mark Bottorff, Gary J. Ferland, Jack Baldwin, Kirk Korista

Physics and Astronomy Faculty Publications

This paper addresses the question, what does the spectrum of a typical quasar reveal about the velocity structure within its broad emission line region clouds? Turbulent (i.e., nonthermal) broadening of spectral lines can be due to macroturbulence or microturbulence. Microturbulence affects line formation and the emitted spectrum and may be required to account for the observed smoothness of the line profiles. The velocity field is crucial since it addresses the fundamental nature of the individual clouds and the global structure of the active galactic nuclei (AGNs) environment. For example, stellar winds or magnetically confined blobs might be highly microturbulent, requiring …

Time Series Analysis Of V815 Herculis Photometry Between 1984 And 1998, Lauri Jetsu, Thomas Hackman, Douglas S. Hall, Gregory W. Henry, Mariitta Kokko, J. You

Information Systems and Engineering Management Research Publications

As a case study of the solar-stellar connection, we have analysed a prolonged time series of BV photometry of the chromospherically active binary V815 Her . The surface differential rotation in the rapidly rotating G5{v} primary caused changes of 4.6% in the seasonal photometric rotation periods. This would imply a differential rotation coefficient of k = 0.184, if the rotation of the starspots follows the solar law of differential rotation and the activity is confined within the same latitudinal range as in the Sun, having k = 0.189 and the spectral-type of G2{v}. Our analysis of the primary and secondary …

Two K Giants With Supermeteoritic Lithium Abundances: Hde 233517 And Hd 9746, Suchitra C. Balachandran, Francis C. Fekel, Gregory W. Henry, Han Uitenbroek

Information Systems and Engineering Management Research Publications

Two unusual Li-rich K giants, HDE 233517 and HD 9746, have been studied. Optical spectroscopy and photometry have been obtained to determine the fundamental parameters of HDE 233517, a single K2 III with an extremely large infrared excess. The spectra yield Teff=4475 K, logg=2.25, [Fe/H]=-0.37, vsini=17.6 km s-1, and a non-LTE logɛ(7Li)=4.22. Photometric observations reveal low-amplitude light variability with a period of 47.9 days. Combined with other parameters, this results in a minimum radius of 16.7 Rsolar and minimum distance of 617 pc. Comparison of spectra obtained in 1994 and 1996 show profile variations in Hα and the Na D …

Lyman-Α Imaging Of A Very Luminous Z = 2.3 Starburst Galaxy With Wfpc2, Nathan Roche, James D. Lowenthal, Bruce Woodgate

Astronomy: Faculty Publications

We investigate the Lyα and UV continuum morphology of one of the most luminous known Lymana emitting galaxies (the 'Coup Fourré Galaxy'), associated with a z = 2.3 damped Lyα absorption system in the spectrum of the QSO PHL 957. The galaxy is observed with the Hubble Space Telescope Wide-Field Planetary Camera 2 (HST WFPC2), through a narrow filter (F410M) corresponding to rest-frame Lyα for a total exposure time of 41.2 ks, plus shorter exposures in F555W and F814W. In all three passbands, the galaxy is resolved into a close (∼0.35 arcsec) pair of two components, CFgA and CFgB, both …

Exospheric Models For The X-Ray Emission From Single Wolf-Rayet Stars., R. Ignace, L. M. Oskinova

Richard Ignace

We review existing ROSAT detections of single Galactic Wolf-Rayet (WR) stars and develop wind models to interpret the X-ray emission. The ROSAT data, consisting of bandpass detections from the ROSAT All-Sky Survey (RASS) and some pointed observations, exhibit no correlations of the WR X-ray luminosity (L_X) with any star or wind parameters of interest (e.g. bolometric luminosity, mass-loss rate or wind kinetic energy), although the dispersion in the measurements is quite large. The lack of correlation between X-ray luminosity and wind parameters among the WR stars is unlike that of their progenitors, the O stars, which show …

Some Applications Of The Lambert W Function To Physics, Sree R. Valluri, David J. Jeffrey, Robert M. Corless

Physics and Astronomy Publications

Two standard physics problems are solved in terms of the Lambert W function, in order to show the applicability of this recently defined function to physics. Other applications of the function are cited, but not described. The problems solved concern Wien’s displacement law and the fringing fields of a capacitor, the latter problem being representative of some problems solved using conformal transformations. The physical content of the solutions remains unchanged, but they gain a new elegance and convenience.

Photometric Variability In A Sample Of 187 G And K Giants, Gregory W. Henry, Francis C. Fekel, Stephen M. Henry, Douglas S. Hall

Information Systems and Engineering Management Research Publications

We have used three automatic photoelectric telescopes to obtain photometric observations of 187 G, K, and (a few) M0 field giants. We find low-amplitude photometric variability on timescales of days to weeks on both sides of the coronal dividing line (CDL) in a total of 81 or 43% of the 187 giants. About one-third of the variables have amplitudes greater than 0.01 mag in V. In our sample the percentage of variable giants is a minimum for late-G spectral classes and increases for earlier and later classes; all K5 and M0 giants are variable. We also obtained high-resolution, red wavelength …

The White Dwarf Cooling Age Of The Open Cluster Ngc 2420, Ted Von Hippel, Gerard Gilmore

Publications

We have used deep HST WFPC2 observations of two fields in NGC 2420 to produce a cluster color-magnitude diagram down to V ≈ 27. After imposing morphological selection criteria we find eight candidate white dwarfs in NGC 2420. Our completeness estimates indicate that we have found the terminus of the WD cooling sequence. We argue that the cluster distance modulus is likely to be close to 12.10 with E(B-V) = 0.04. With these parameters we find a white dwarf cooling age for NGC 2420 of 2.0 ± 0.20 (1 σ) Gyr. The 0.20 Gyr uncertainty includes errors in the photometry, …

Low-Mass Spectroscopic Binaries In The Hyades: A Candidate Brown Dwarf Companion, I. Neill Reid, S. Mahoney

Dartmouth Scholarship

We have used the HIRES echelle spectrograph on the Keck I telescope to obtain high-resolution spectroscopy of 51 late-type M dwarfs in the Hyades cluster. Cross-correlating the calibrated data against spectra of white dwarfs allows us to determine heliocentric velocities with an accuracy of ±0.3 km s⁻¹. 27 stars were observed at two epochs in 1997; two stars, RHy 42 and RHy 403, are confirmed spectroscopic binaries. RHy 42 is a double-lined, equal-mass system; RHy 403 is a single-lined, short-period binary, P∼1.275 d. RHy 403A has an absolute magnitude of M_I=10.85, consistent with a mass …

Clathrate Structure For Electronic And Electro-Optic Applications, Leonid Grigorian, Peter C. Eklund, Shaoli Fang

Physics and Astronomy Faculty Patents

A method including the steps of (a) depositing a metal layer on a selected portion of a silicon substrate under a first set of predetermined conditions to form an metal silicide layer and an intermediate n-type silicon layer; and (b) exposing the metal silicide layer and the n-type silicon layer to a second set of predetermined conditions to form a silicon clathrate film on the selected portion of the silicon substrate, where the intermediate n-type silicon layer acts to bond the silicon clathrate to the silicon substrate to form a silicon clathrate structure.

The Narrow-Line Region In The Seyfert 2 Galaxy Ngc 3393, Andrew J. Cooke, J. A. Baldwin, Gary J. Ferland, Hagai Netzer, Andrew S. Wilson

Physics and Astronomy Faculty Publications

The narrow-line region (NLR) of the Seyfert 2 galaxy NGC 3393 is dominated by a symmetric structure which appears as S-shaped arms in Hubble Space Telescope (HST) images. These arms, which occupy the central few arcseconds of the nucleus, border a linear, triple-lobed radio source. We use HST imaging and spectra, ground-based optical images, long-slit spectra, Fabry-Perot imaging spectroscopy, and VLA radio data to perform a detailed investigation of the kinematics and ionization of the line-emitting gas in NGC 3393 and of its relationship with the relativistic gas responsible for the radio emission. The excitation map [O III] …