Astrophysics and Astronomy Commons^™

Upper Limits To The Nightside Ionosphere Of Mars, Jane L. Fox

Physics Faculty Publications

The nightside ionosphere of Mars could be produced by electron precipitation or by plasma transport from the dayside, by analogy to the Venus, but few measurements are available. We report here model calculations of upper limits to the nightside ion densities on Mars that would be produced by both mechanisms. For the auroral model, we have adopted the downward traveling portions of the electron spectra measured by the HARP instrument on the Soviet Phobos spacecraft in the Martian plasma sheet and in the magnetotail lobes. For the plasma transport case, we have imposed on a model of the nightside thermosphere, …

Ccd Photometry Of The Old Open Cluster M67, Kent A. Montgomery, Laurence A. Marschall, Kenneth A. Janes

Physics and Astronomy Faculty Publications

We present a CCD photometric survey of the central one-half degree of the old open cluster, M67, in U, B, V, and I colors to magnitude V=20. Extensive comparison of our photometry with other published datasets shows excellent agreement, indicating that CCD photometry is capable of producing a uniform set of measurements consistent with the photometric system defined primarily by the Landolt standard sequence. The color-magnitude diagram of the cluster shows a well-defined main sequence extending at least to the limit of the photometry at Mv=10.55 and a substantial binary sequence. At least 38% of cluster stars are …

The Narrow-Line Region Of High-Luminosity Active Galactic Nuclei, Beverley J. Wills, H. Netzer, M. S. Brotherton, Mingsheng Han, D. Wills, J. A. Baldwin, Gary J. Ferland, I. W. A. Browne

Physics and Astronomy Faculty Publications

We have made high signal-to-noise spectroscopic observations of seven radio-loud quasars with the Faint Object Spectrograph on the Hubble Space Telescope and from the ground at McDonald Observatory and at Kitt Peak National Observatory. The resolution is 300-400 km s^-1 over the wavelength range 1000-8500 Å, enabling us to separate the broad and narrow components of the emission lines. This is the first study of the optical and UV narrow lines in such high-luminosity active galactic nuclei (AGNs).

The most important and striking observational result is the relative weakness of the narrow ultraviolet lines, assuming that they have …

The Dynamics Of Stellar Outflows Dominated By Interaction Of Dust And Radiation, Nathan Netzer, Moshe Elitzur

Physics and Astronomy Faculty Publications

Wind outflow around a late-type star driven by radiation pressure on dust grains is investigated in detail. The equation of motion for the outflow coupled with the equation of radiative transfer is solved treating the circumstellar envelope, which consists of gas and dust, as a two-component fluid. Because of the drift of the dust particles through the gas, the dust-to-gas ratio varies with distance even if grain formation is a prompt process. The coupling between dust and gas weakens as the mass-loss rate decreases until finally the rate of momentum transfer to the gas is insufficient to overcome gravity when …

Chromospherically Active Stars. X. Spectroscopy And Photometry Of Hd 212280, Francis C. Fekel, Jared C. Browning, Gregory W. Henry, Mary D. Morton, Douglas S. Hall

Information Systems and Engineering Management Research Publications

The system HD 212280 is a chromospherically active double lined spectroscopic binary with an orbital period of 45.284 days and an eccentricity of 0.50. The spectrum is composite with spectral types of G8 IV and F5-8 V for the components. An estimated inclination of 78 +/- 8 deg results in masses of 1.7 and 1.4 solar mass for the G subgiant and mid-F star, respectively. The distance to the system is estimated to be 112 pc. Photometric observations obtained between 1987 November and 1992 June reveal that HD 212280 is a newly identified variable star with a V amplitude of …

Photometric And Spectroscopic Observations Of Sn 1990e In Ngc 1035: Observational Constraints For Models Of Type Ii Supernovae, Brian P. Schmidt, Robert P. Kirshner, Rudolph Schild, Bruno Leibundgut, David Jeffery, S. P. Willner, Reynier Peletier, Ann I. Zabludoff, Mark M. Phillips, Nicholas B. Suntzeff, Mario Hamuy, Lisa A. Wells, Chris Smith, Jack A. Baldwin, W. G. Weller, M. Navarette, L. Gonzalez, Alexei V. Filippenko, Joseph C. Shields, Charles C. Steidel, Saul Perlmutter, Carlton R. Pennypacker, Craig K. Smith, Alain C. Porter, Todd A. Boroson, Raylee Stathakis, Russell Cannon, J. Peters, E. Horine, Kenneth C. Freeman, Donna S. Womble, Remington P.S. Stone, Laurence A. Marschall, Andrew C. Phillips, A. Saha, Howard E. Bond

Physics and Astronomy Faculty Publications

We present 126 photometric and 30 spectral observation of SN 1990E spanning from 12 days before B maximum to 600 days past discovery. These observations show that SN 1990E was of type II-P, displaying hydrogen in its spectrum, and the characteristic plateau in its light curve. SN 1990E is one of the few SNe II which has been well observed before maximum light, and we present evidence that this SN was discovered very soon after its explosion. In the earliest spectra we identify, for the first time, several N II lines. We present a new technique for measuring extinction to …

Digital Imaging In The Introductory Astronomy Course, Laurence A. Marschall, Michael B. Hayden

Physics and Astronomy Faculty Publications

The availability of small, inexpensive CCD cameras is making it possible to offer non-science students in introductory astronomy courses hands-on experience in astronomical imaging. For the past three years at Gettysburg College we have been developing laboratory exercises using ST-4, ST-6, and Lynxx CCD cameras attached to 8-inch telescopes. We discuss the hardware and the procedures involved in these exercises, pointing out the benefits and limitations of digital observations with introductory students. We also offer tips for making successful observations with students, and describe plans for further development.

Instrument Description And Performance Of The Imaging Gamma-Ray Telescope Comptel Aboard The Compton Gamma-Ray Observatory, V. Schonfelder, H. Aarts, K Bennett, H Deboer, J. Clear, W Collmar, A Connors, A. Deerenberg, R Diehl, A. Von Dordrecht, J W. Den Herder, W Hermsen, R M. Kippen, L Kuiper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, G. Simpson, M. Snelling, G Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, C De Vries, C Winkler

Space Science Center

The COMPTEL instrument aboard the COMPTEL Gamma-Ray Observatory and its performance capabilities are described. Calibration data are used to determine the angular and energy response, and the effective detection area. The imaging properties of COMPTEL are demonstrated, and the sensitivity of Comptel to celestial gamma-ray sources are estimated from flight data.

Large Amplitude L=1 Coherent Structures In Non-Neutral Plasmas Confined In A Cylindrical Trap, Ross L. Spencer, Grant W. Mason

Faculty Publications

The computation of l= 1 coherent structures in non-neutral plasmas with arbitrary density profiles and for large displacements of the plasma from the symmetry axis of a confining cylindrical trap is described. As the structures are displaced from the axis, they revolve about the symmetry axis with a frequency that typically increases with displacement. The plasma also is distorted into an approximately elliptical shape. The frequency shifts and the eccentricities as a function of displacement, plasma size, and the shape of the density profile are both computed numerically and calculated analytically. The results are shown to be consistent with data …

Photoluminescence And Absorption Studies Of Defects In Cdte And Znxcd1-Xte Crystals, Cheryl Barnett Davis, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Ovidio González, Bret C. Hess, Worth P. Allred

Faculty Publications

We have studied at cryogenic temperatures photoluminescence features which lie more than 0.15 eV below the band edge in ZnxCd1-xTe (0≤x≤0.09) crystals. The same features, namely a defect band which lies at about 0.13-0.20 eV below the band-gap energy and a peak at 1.1 eV, that are observed in pure CdTe samples are observed in these alloy materials. In annealed samples we observe that the 1.1 eV feature, which has been attributed to tellurium vacancies, increases with fast cooling. Increased concentrations of tellurium vacancies can be understood in terms of the phase diagram of CdTe which indicates that higher concentrations …

Photoelectric And Ccd Photometry Of E And S0 Galaxies, M. Colless, D. Burstein, G. Wegner, R. P. Saglia

Dartmouth Scholarship

We present BR photoelectric photometry for 352 E and S0 galaxies that are part of a large survey of the properties and peculiar motions of galaxies in distant clusters. Repeat measurements show our internal errors to be 2 – 3 per cent in B and R and 1 – 2 per cent in B– R. Comparisons of BR and BVR reductions for 10 galaxies also observed in V show small systematic errors due to differences between the spectral energy distributions of stars and galaxies. External comparisons with B– V colours in the literature confirm that these colours are …

Observations Of The Ca Ii Infrared Triplet In Chromospherically Active Single And Binary Stars, Robert C. Dempsey, Bernard W. Bopp, Gregory W. Henry, Douglas S. Hall

Information Systems and Engineering Management Research Publications

Spectroscopic observations of the Ca II infrared triplet (8498, 8542, 8662 A) have been obtained for 45 stars which are known or suspected to be chromospherically active. The sample includes both single and binary stars of spectral types from F2 to M5 spanning luminosity classes III, IV, and V. Several different types of activity diagnostics were measured, and their relative merits are discussed. Dependence of chromospheric emission upon rotation period, luminosity, temperature, and duplicity are analyzed. Synchronous binaries show a slight trend of increased emission with decreasing period while the asynchronous binaries show abnormally high activity levels for their rotation …

Distinguishing A Charged Higgs Signal From A Heavy Wr Signal, David I. Kaiser

Dartmouth Scholarship

It is shown that non-Standard Model bosons should obey an observable asymmetry in their decays to taus. This asymmetry enables a distinction to be made between charged Higgsboson signalsand heavy right-handed Wboson signals,by reconstructing the orientation of the z with respect to the beam axis.

Microjansky Source Counts And Spectral Indices At 8.44 Ghz, Rogier A. Windhorst, Edward B. Fomalont, R. Bruce Partridge, James D. Lowenthal

Astronomy: Faculty Publications

We used the VLA to make deep images of two 7′ × 7′ fields at 8.44 GHz with 10″ resolution. With an rms noise of 3.2 and 5.1 μJy, respectively, in the two fields, we compiled a catalog of 82 sources. From the complete sample of 20 sources with S ≥ 14.5 μJy, the differential 8.44 GHz source count is dN(S)/ dS = (-4.6 ± 0.7) × S-2.3 ± 0.2 Jy-1 sr-1 in the range 14.5-1000 mJy. Analysis of statistical image fluctuations from weak sources (Fomalont et al. 1993) suggests that this slope remains unchanged at γ = 2.3 ± …

The Triple Symbiotic System Ch Cygni, Kenneth H. Hinkle, Francis C. Fekel, Diana S. Johnson, Werner W.G. Scharlach

Information Systems and Engineering Management Research Publications

Analysis of high-resolution IR spectra of CH Cygni shows that the star is a triple system with a short period orbit of just over 2 yrs. The period ratio of seven for CH Cyg is the smallest known for a triple system. The symbiotic pair is the short-period system. An eccentric and a circular orbit solution are determined for the short-period pair, and the circular orbit solution is found to be more appropriate. The observed eccentricity appears to be due to phase-dependent line asymmetries resulting from the irradiation of the M giant by the white dwarf. The system does not …

The Measurement Of Astronomical Parallaxes With Ccd Imaging Cameras On Small Telescopes, Stephen J. Ratcliff, Thomas J. Balonek, Laurence A. Marschall, David L. Dupuy, Carlton R. Pennypacker, Ritu Verma, Anastasia Alexov, Vivian Bonney

Physics and Astronomy Faculty Publications

Small telescopes equipped with charge-coupled device (CCD) imaging cameras are well suited to introductory laboratory exercises in positional astronomy (astrometry). An elegant example is the determination of the parallax of extraterrestrial objects, such as asteroids. For laboratory exercises suitable for introductory students, the astronomical hardware needs are relatively modest, and under the best circumstances, the analysis requires little more than arithmetic and a microcomputer with image display capabilities. Results from the first such coordinated parallax observations of asteroids ever made are presented. In addition, procedures for several related experiments, involving single-site observations and/or parallaxes of earth-orbiting artificial satellites, are outlined.

Low-Frequency Feature In The First-Order Raman Spectrum Of Amorphous Carbon, David D. Allred, Qi Wang, Jesus González-Hernández

Faculty Publications

In the first-order Raman spectrum of amorphous carbon (a-C) there is a low-frequency feature in the 200-900-cm-1 region. This feature is characteristic of the highly disordered amorphous-carbon materials. We note that the intensity of this feature is very sensitive to the thermal history of samples, thus suggesting that it is an important measure of the degree of disorder of the a-C materials. We also discuss the relationship between this feature and the phonon density of states of graphite.

Exponential Growth Of An Unstable L=1 Diocotron Mode For A Hollow Electron Column In A Warm-Fluid Model, S. Neil Rasband, Ross L. Spencer, Richard R. Vanfleet

Faculty Publications

Numerical investigations of a warm-fluid model with an isothermal equation of state for the perpendicular dynamics of an axisymmetric, magnetically confined pure electron plasma predict an exponentially unstable, l=1, diocotron mode for hollow density profiles. The unstable mode can be identified with a stable, nonsmooth mode that exists in cold drift models but which is destabilized by finite temperature effects. The unstable mode has many properties similar to the experimental results reported by Driscoll [Phys. Rev. Lett. 64, 645 (1990)].

Limits To Cosmic Background Radiation Fluctuations At 8.44 Ghz Between Angular Scales 10″ And 200″, Edward B. Fomalont, R. Bruce Partridge, James D. Lowenthal, Rogier A. Windhorst

Astronomy: Faculty Publications

We have used the VLA at 8.44 GHz to measure fluctuations in the cosmic background radiation (CBR) from two deep images, each 7′ x 7′ in size. No fluctuations between the angular scales 10″ and 200″ were detected. The most accurate limit (95% confidence) is ΔT/TCBR < 1.9 x 10-5 for 80″ resolution. For random Gaussian fluctuations with coherence angle θc, the limits are ΔT/TCBR < 30 x 10-5 for 22″ < θc < 60″. Outside this range the limits increase to ΔT/TCBR < 5 x 10-5 at θc = 12″ or 100″ and ΔT/TCBR < 10 x 10-5 at θc = 5″ or 120″. Similar limits have been obtained for the circularly and linearly polarized components of the CBR fluctuations. These limits were derived from the residual fluctuations in the images after (1) removing brighter foreground sources (> 14.5 μJy) which covered about 10% of each image; (2) estimating fluctuations of weaker sources by extrapolating the count of dN/dS = 4.6S-2.3 Jy-1 sr-1 to 4 μJy; and (3) determining fluctuations from receiver noise and instrumental errors by comparing the image variances from two independent halves of the data set. All analysis was …

Lithium And Rapid Rotation In Chromospherically Active Single Giants, Francis C. Fekel, Suchitra C. Balachandran

Information Systems and Engineering Management Research Publications

The rotational velocities presently obtained via spectroscopic observations of a group of moderately rapidly rotating, chomospherically active single giants indicate that Gray's (1989) rotostat hypothesis requires modification. Their rapid rotation appears to be due to high Li abundances, and results in increased chromospheric activity. A scenario is projected in which the surface convection zone reaches the rapidly rotating core just as a star begins its first ascent of the giant branch, and dredges both high angular momentum material and freshly synthesized Li to the surface.

Black Holes And Singularities, Andrew Lang

College of Science and Engineering Faculty Research and Scholarship

First, I give definitions and mathematical preliminaries. Secondly, I give a history of the derivation of Einstein's field equations. From this basis, I present a derivation of Schwarzschild's solution. A discussion then follows of various types of black holes: stationary, charged, rotating, and charged/rotating. I also give a pictorial representation of the properties of each algebraically special solution. Finally, I present a general definition of singularities along with a discussion of closed trapped surfaces and naked singularities.

Quantam Wave Turbulence, Alejandro Garcia, M. Haeri, S. Putterman, P. Roberts

Faculty Publications

The nonlinear quantum kinetic equation for the interaction of sound waves is solved via analytic and numerical techniques. In the classical regime energy cascades to higher frequency (ω) according to the steady-state power law ω-3/2. In the quantum limit, the system prefers a reverse cascade of energy which follows the power law ω-6. Above a critical flux, a new type of spectrum appears which is neither self-similar nor close to equilibrium. This state of nonlinear quantum wave turbulence represents a flow of energy directly from the classical source to the quantum degrees of freedom.

Time Projection Chamber's Efficiency, Obtained Using Cern's Geant Code, Christine A. Byrd, Charles M. Byrd, Wilfred J. Braithwaite

Journal of the Arkansas Academy of Science

Geometrical acceptance and reconstruction of tracks have been carried out for a Time Projection Chamber (TPC) used in Experiment NA35: the 35th experiment in the North Area of the Super Proton Synchrotron (SPS), located at the European Organization for Nuclear Research (CERN). NA35 used the SPS at CERN to produce 6.4 TeV beams of 32S for central collisions with Au nuclei. The TPC modeling effort used a modified version of CERN's Monte Carlo program GEANT, which simulates the response of the NA35 TPC to output from CERN's primary event generators. GEANT was used to simulate three-dimensional pixel data in the …

Alfvén Solitons And The Dnls Equation, Robert L. Hamilton, C F. Kennel, E Mjølhus

Faculty Publications - Department of Mathematics

No abstract provided.

The Soliton Transform And A Possible Application To Nonlinear Alfvén Waves In Space, T Hada, Robert L. Hamilton, C F. Kennel

Faculty Publications - Department of Mathematics

We apply the inverse scattering transform (1ST) based upon the Derivative Nonlinear Schrödinger (DNLS) equation to a complex time series of nonlinear Alfvén wave data generated by numerical simulation. The IST describes the long-time evolution of quasi-parallel Alfvén waves more efficiently than the Fourier transform, which is adapted to linear, not nonlinear, problems. When we add dissipation, so the conditions for the validity of the DNLS are not strictly satisfied, the IST continues to provide a compact description of the wavefield in terms of a small number of decaying envelope solitons. Since large amplitude Alfven waves and other nonlinear waves …

Search For Gamma‐Ray Emission From Agn With Comptel, W Collmar, R Diehl, G G. Lichti, V Schonfelder, H Steinle, A W. Strong, H Bloemen, J W. Den Herder, W Hermsen, B Swanenburg, C De Vries, Mark L. Mcconnell, James M. Ryan, G Stacy, K Bennett, O R. Williams, C Winkler

Space Science Center

The COMPTEL data (∼0.7–30 MeV) were searched for emission from AGN. Four sources have been detected so far: the quasars 3C 273, 3C 279, PKS 0528+134, and the radio galaxy Centaurus A. 3C 273 and 3C 279 were detected in CGRO observation period 3 with quite different spectral shapes. There is also evidence for 3C 273 at a weak flux level in observation period 11. The quasar PKS 0528+134 was detected above 3 MeV as part of a search for AGN already observed by EGRET. Cen A was seen up to 3 MeV by combining data from different observation periods.

Comptel Observations Of Gamma-Ray Bursts - Imaging And Localization, A Connors, H Aarts, K Bennett, H Bloemen, H Deboer, M Busetta, W Collmar, R Diehl, R Van Dijk, L O. Hanlon, J W. Den Herder, W Hermsen, R M. Kippen, L Kuiper, A. Klumper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, G. Simpson, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, M Varendorff, C De Vries, W Webber, O R. Williams, C Winkler

Space Science Center

The COMPTEL experiment on GRO images 0.7-30 MeV celestial gamma-radiation that falls within its 1 steradian field of view. During the first eleven months of orbit, preliminary lozalizations from BATSE triggers indicated that about 1 in 6 cosmic events could have fallen within COMPTEL's field of view. WE present COMPTEL positions for four of the brighter of these gamma-ray bursts.

Gamma‐Ray Burst Studies By Comptel During Its First Year Of Operation, C Winkler, K Bennett, L O. Hanlon, O R. Williams, W Collmar, R Diehl, V Schonfelder, H Steinle, M Varendorff, J W. Den Herder, W Hermsen, L Kuiper, B Swanenburg, C De Vries, A Connors, D J. Forrest, R M. Kippen, Mark L. Mcconnell, James M. Ryan

Space Science Center

During the first year of Compton GRO operations, more than 20 cosmic gamma‐ray burst‐detected by the BATSE instrument ‐ occurred inside the 1 sr field of view of the imaging gamma‐ray telescope COMPTEL. Using COMPTEL’s primary mode of operation (the telescope mode) direct images (with ∼1° GRB location accuracy) and event spectra (0.7 MeV – 30 MeV) with spectral resolution better than 10% FWHM have been obtained. In its secondary mode of burst operations, COMPTEL has recorded time resolved spectra (0.1 MeV – 10 MeV) from its large NaI detectors. This paper summarises the results on cosmic GRB sources obtained …

Initial Results From Comptel—An Overview, V Schonfelder, W Collmar, R Diehl, G G. Lichti, H Steinle, A W. Strong, M Varendorff, H Bloemen, H Deboer, R Vandijk, J W. Den Herder, W Hermsen, L Kuiper, B Swanenburg, C De Vries, A Connors, D J. Forrest, Mark L. Mcconnell, D Morris, James M. Ryan, G Stacy, K Bennett, C Winkler, B G. Taylor

Space Science Center

COMPTEL is presently completing the first full sky survey in MeV gamma‐ray astronomy (0.7 to 30 MeV). An overview of initial results from the survey is given: among these are the observations of the Crab and Vela pulsars with unprecedented accuracy, the observation of the black hole candidates Cyg X‐1 and Nova Persei 1992, an analysis of the diffuse Galactic continuum emission from the Galactic center region, the broad scale distribution of the 1.8 MeV line from radioactive ^{2 6}Al, upper limits on gamma‐ray line emission from SN 1991T, observations of the three quasars 3C273, 3C279 and PKS 0528+134 …

Comptel Observations Of Gamma-Ray Bursts - Time Profiles And Spectra, W Collmar, K Bennett, H Bloemen, H Deboer, M Busetta, A Connors, R Diehl, J Greiner, L O. Hanlon, J W. Den Herder, W Hermsen, L Kuiper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, M Varendorff, C De Vries, W Webber, O R. Williams, C Winkler

Space Science Center

The COMPTEL experiment aboard CGRO is designed to image celestial gamma-radiation in the energy range from 0.7-30 MeV, and also to accumulate time-resolved NaI detector spectra (0.1-10 MeV) upon receipt of a BATSE burst trigger signal. During the early phases of the GRO mission several bursts have been observed. In this paper we present time profiles and first results from spectral analysis for GRB 910425, GRB 910601, and GRB 910814.