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Embry-Riddle Aeronautical University

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2005

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Articles 1 - 30 of 33

Full-Text Articles in Physical Sciences and Mathematics

The Dust Cloud Around The White Dwarf G29-38, William T. Reach, Ted Von Hippel, Et Al. Dec 2005

The Dust Cloud Around The White Dwarf G29-38, William T. Reach, Ted Von Hippel, Et Al.

Publications

We present new observations of the white dwarf G29-38 with the camera (4.5 and 8 μm), photometer (24 μm), and spectrograph (5.5-14 μm) of the Spitzer Space Telescope. This star has an exceptionally large infrared excess, amounting to 3% of the bolometric luminosity. The spectral energy distribution (SED) has a continuum peak around 4.5 μm and a 9-11 μm emission feature 1.25 times brighter than the continuum. A mixture of amorphous olivine and a small amount of forsterite in an emitting region 1-5 R☉ from the star can reproduce the shape of the 9-11 μm feature. The SED …


A Multisite Photometric Campaign On The Pre-Main-Sequence ₰ Delta Scuti Pulsator Ip Per, V. Ripepi, T. D. Oswalt, S. Bernabei, M. Marconi, Et Al. Dec 2005

A Multisite Photometric Campaign On The Pre-Main-Sequence ₰ Delta Scuti Pulsator Ip Per, V. Ripepi, T. D. Oswalt, S. Bernabei, M. Marconi, Et Al.

Publications

We present the results of a photometric multisite campaign on the δ Scuti Pre-Main-Sequence star IP Per. Nine telescopes have been involved in the observations, with a total of about 190 h of observations over 38 nights. Present data confirms the multiperiodic nature of this star and leads to the identification of at least nine pulsational frequencies. Comparison with the predictions of linear non-adiabatic radial pulsation models allowed us to identify only five of the nine observed frequencies, and to constrain the position of IP Per in the HR diagram. The latter is in good agreement with the empirical determination …


Book Review: Stargazer: The Life And Times Of The Telescope, T. D. Oswalt Dec 2005

Book Review: Stargazer: The Life And Times Of The Telescope, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Stargazer : the Life and Times of the Telescope by Fred Watson. Da Capo, 2004 342p, 0306814323 $24.95


Measuring The Evolution Of The Most Stable Optical Clock G 117-B15a, S. O. Kepler, Ted Von Hippel, Et Al. Dec 2005

Measuring The Evolution Of The Most Stable Optical Clock G 117-B15a, S. O. Kepler, Ted Von Hippel, Et Al.

Publications

We report our measurement of the rate of change of period with time () for the 215 s periodicity in the pulsating white dwarf G 117-B15A, the most stable optical clock known. After 31 years of observations, we have finally obtained a 4 σ measurement observed = (4.27 ± 0.80) × 10-15 s s-1. Taking into account the proper-motion effect of proper = (7.0 ± 2.0) × 10-16s s-1, we obtain a rate of change of period with time of = (3.57 ± 0.82) × 10-15 s s-1. This value is consistent with the cooling rate in our white dwarf …


Faint Blue Objects In The Hubble Deep Field–South Revealed: White Dwarfs, Subdwarfs, And Quasars, Mukremin Kilic, Ted Von Hippel, Et Al. Nov 2005

Faint Blue Objects In The Hubble Deep Field–South Revealed: White Dwarfs, Subdwarfs, And Quasars, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We explore the nature of the faint blue objects in the Hubble Deep Field–South. We have derived proper motions for the point sources in the Hubble Deep Field–South using a 3 yr baseline. Combining our proper-motion measurements with spectral energy distribution fitting enabled us to identify four quasars and 42 stars, including three white dwarf candidates. Two of these white dwarf candidates, HDF-S 1444 and 895, are found to display significant proper motion, 21:1±7:9 and 34:9 ± 8:0 mas yr -1, and are consistent with being thick-disk or halo white dwarfs located at ̴2 kpc. The other faint …


Modification Of Precipitation By Coastal Orography In Storms Crossing Northern California, Curtis N. James, Robert A. Houze Jr. Nov 2005

Modification Of Precipitation By Coastal Orography In Storms Crossing Northern California, Curtis N. James, Robert A. Houze Jr.

Applied Aviation Sciences - Prescott

This study compiles and interprets three-dimensional Weather Surveillance Radar-1988 Doppler (WSR-88D) data during a 2.5-yr period and examines the typical orographic effects on precipitation mainly associated with winter storms passing over coastal northern California.The three-dimensional mean reflectivity patterns show echo structure that was generally stratiform from over the ocean to inland over the mountains. The flow above the 1-km level was strong enough to be unblocked by the terrain, and the mean echo pattern over land had certain characteristics normally associated with an unblocked cross-barrier flow, both on the broad scale of the windward slopes of the coastal mountains and …


Book Review: The Scientific Legacy Of Fred Hoyle, T. D. Oswalt Nov 2005

Book Review: The Scientific Legacy Of Fred Hoyle, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Scientific Legacy of Fred Hoyle ed. by Douglas Gough Cambridge, 2004 249p, 0521824486 $75.00.


Coordinated Cluster/Double Star Observations Of Dayside Reconnection Signatures, M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, K. Nykyri, Et Al. Nov 2005

Coordinated Cluster/Double Star Observations Of Dayside Reconnection Signatures, M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, K. Nykyri, Et Al.

Publications

The recent launch of the equatorial spacecraft of the Double Star mission, TC-1, has provided an unprecedented opportunity to monitor the southern hemisphere dayside magnetopause boundary layer in conjunction with northern hemisphere observations by the quartet of Cluster spacecraft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 spacecraft were on outbound transits through the dawnside magnetosphere. The observations are consistent with ongoing reconnection on the dayside magnetopause, resulting in a series of flux transfer events (FTEs) seen both at Cluster and TC-1, which appear to lie north and …


Acoustic Waves Generated By Gusty Flow Over Hilly Terrain, R. L. Walterscheid, Michael P. Hickey Ph.D. Oct 2005

Acoustic Waves Generated By Gusty Flow Over Hilly Terrain, R. L. Walterscheid, Michael P. Hickey Ph.D.

Publications

We examine the generation of acoustic waves by gusty flow over hilly terrain. We use simple theoretical models of the interaction between terrain and eddies and a linear model of acoustic-gravity wave propagation. The calculations presented here suggest that over a dense array of geographically extensive sources orographically generated vertically propagating acoustic waves can be a significant cause of thermospheric heating. This heating may account in good part for the thermospheric hot spot near the Andes reported by Meriwether et al. (1996, 1997).


Excess Infrared Radiation From The Massive Daz White Dwarf Gd 362: A Debris Disk?, Mukremin Kilic, Ted Von Hippel, Et Al. Oct 2005

Excess Infrared Radiation From The Massive Daz White Dwarf Gd 362: A Debris Disk?, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We report the discovery of excess K-band radiation from the massive DAZ white dwarf star GD 362. Combining infrared photometric and spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a debris disk. This would be only the second such system known, discovered 18 years after G29-38, the only single white dwarf currently known to be orbited by circumstellar dust. Both of these systems favor a model with accretion from a surrounding debris disk to explain the metal abundances observed in DAZ white dwarfs. …


Deep Photometry Of The Globular Cluster M5: Distance Estimates From White Dwarf And Main-Sequence Stars, Andrew C. Layden, Ted Von Hippel, Et Al. Oct 2005

Deep Photometry Of The Globular Cluster M5: Distance Estimates From White Dwarf And Main-Sequence Stars, Andrew C. Layden, Ted Von Hippel, Et Al.

Publications

We present deep VI photometry of stars in the globular cluster M5 (NGC 5904) based on images taken with the Hubble Space Telescope. The resulting color-magnitude diagram reaches below V ≈27 mag, revealing the upper 2–3 mag of the white dwarf cooling sequence and main-sequence stars 8 mag and more below the turnoff. We fit the main sequence to subdwarfs of known parallax to obtain a true distance modulus of (m ̶ M )0 = 14:45 ± 0:11 mag. A second distance estimate based on fitting the cluster white dwarf sequence to field white dwarfs with known parallax …


Integration Of The Shel Model With The Flight Operational Quality Assurance (Foqa) Program, James T. Schultz, Scott Forn, Marian C. Schultz Oct 2005

Integration Of The Shel Model With The Flight Operational Quality Assurance (Foqa) Program, James T. Schultz, Scott Forn, Marian C. Schultz

Publications

The SHEL Model has been used to explore relationships between liveware, environmental, hardware and software factors. This study attempts to integrate Flight Operational Quality Assurance (FOQA) program data with the SHEL model. Aircraft record data that can be used to monitor the human interface within the entire system, plus identify faults and potential failures within the system before a major accident or incident occurs. These data have existed for over four decades, and FOQA offers a way to both analyze and act upon them. The relationships between the SHEL model and FOQA data can help to ensure our nation's skies …


Galactic Open Clusters, Ted Von Hippel Sep 2005

Galactic Open Clusters, Ted Von Hippel

Publications

The study of open clusters has a classic feel to it since the subject predates anyone alive today. Despite the age of this topic, I show via an ADS search that its relevance and importance in astronomy has grown faster in the last few decades than astronomy in general. This is surely due to both technical reasons and the interconnection of the field of stellar evolution to many branches of astronomy. In this review, I outline what we know today about open clusters and what they have taught us about a range of topics from stellar evolution to Galactic structure …


Book Review: Observing Variable Stars, Novae, And Supernovae, T. D. Oswalt Sep 2005

Book Review: Observing Variable Stars, Novae, And Supernovae, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Observing Variable Stars, Novae, and Supernovae by Gerald North with Nick James Cambridge, 2004 230p, 0521820472 $45.00.


Where Are The Magnetic White Dwarfs With Detached, Nondegenerate Companions?, James W. Liebert, Dayal T. Wickramsinghe, Gary D. Schmidt, Nicole M. Silvestri, T. D. Oswalt, Et Al. May 2005

Where Are The Magnetic White Dwarfs With Detached, Nondegenerate Companions?, James W. Liebert, Dayal T. Wickramsinghe, Gary D. Schmidt, Nicole M. Silvestri, T. D. Oswalt, Et Al.

Publications

The Sloan Digital Sky Survey has already more than doubled the sample of white dwarfs with spectral classifications, the subset with detached M dwarf companions, and the subset of magnetic white dwarfs. In the course of assessing these new discoveries, we have noticed a curious, unexpected property of the total lists of magnetic white dwarfs and of white dwarf plus main-sequence binaries: there appears to be virtually zero overlap between the two samples! No confirmed magnetic white dwarf has yet been found in such a pairing with a main-sequence star. The same statement can be made for the samples of …


Antiphase Oh And Oi Airglow Emissions Induced By A Short-Period Ducted Gravity Wave, Jonathan B. Snively, Victor P. Pasko Apr 2005

Antiphase Oh And Oi Airglow Emissions Induced By A Short-Period Ducted Gravity Wave, Jonathan B. Snively, Victor P. Pasko

Publications

"Numerical simulation of a ducted gravity wave event suggests that OH (8,3) and O(1S) 557.7 nm airglow emissions layers may exhibit opposite-phase intensities when perturbed by a short-period wave undergoing vertical reflection. This effect arises due to the time and temperature dependance of the OH excitation reaction, coupled with the linear polarization properties of vertically-standing waves."


Physical Processes In Acoustic Wave Heating Of The Thermosphere, G. Schubert, Michael P. Hickey Ph.D., R. L. Walterscheid Apr 2005

Physical Processes In Acoustic Wave Heating Of The Thermosphere, G. Schubert, Michael P. Hickey Ph.D., R. L. Walterscheid

Publications

Upward propagating acoustic waves heat the atmosphere at essentially all heights due to effects of viscous dissipation, sensible heat flux divergence, and Eulerian drift work. Acoustic wave-induced pressure gradient work provides a cooling effect at all heights, but this is overwhelmed by the heating processes. Eulerian drift work and wave-induced pressure gradient work dominate the energy balance, but they nearly cancel at most altitudes, leaving their difference, together with viscous dissipation and sensible heat flux divergence to heat the atmosphere. Acoustic waves are very different from gravity waves which cool the upper atmosphere through the effect of sensible heat flux …


Observations Of Gravity Wave Breakdown Into Ripples Associated With Dynamical Instabilities, Feng Li, Alan Z. Liu, Gary R. Swenson, James H. Hecht, Walter A. Robinson Mar 2005

Observations Of Gravity Wave Breakdown Into Ripples Associated With Dynamical Instabilities, Feng Li, Alan Z. Liu, Gary R. Swenson, James H. Hecht, Walter A. Robinson

Physical Sciences - Daytona Beach

The breakdown of a high-frequency quasi-monochromatic gravity wave into smallscale ripples in OH airglow was observed on the night of 28 October 2003 at Maui, Hawaii (20.7ºN, 156.3ºW). The ripples lasted ~20 min. The phase fronts of the ripples were parallel to the phase fronts of the breaking wave. The mechanism for the ripple generation is investigated using simultaneous wind and temperature measurements made by a sodium (Na) lidar. The observations suggest that the wave breaking and the subsequent appearance of ripples were related to dynamical (or Kelvin-Helmholtz) instabilities. The characteristics of the ripples, including the alignment of the phase …


From Young And Hot To Old And Cold: Comparing White Dwarf Cooling Theory To Main-Sequence Stellar Evolution In Open Clusters, Ted Von Hippel Mar 2005

From Young And Hot To Old And Cold: Comparing White Dwarf Cooling Theory To Main-Sequence Stellar Evolution In Open Clusters, Ted Von Hippel

Publications

I explore the current ability of both white dwarf cooling theory and main-sequence stellar evolution theory to accurately determine stellar population ages by comparing ages derived using both techniques for open clusters ranging from 0.1 to 4 Gyr. I find good agreement between white dwarf and main-sequence evolutionary ages over the entire age range currently available for study. I also find that directly comparing main-sequence turnoff ages to white dwarf ages is only weakly sensitive to realistic levels of errors in cluster distance, metallicity, and reddening. Additional detailed comparisons between white dwarf and main-sequence ages have tremendous potential to refine …


Observational Investigations Of Gravity Wave Momentum Flux With Spectroscopic Imaging, J. Tang, G. R. Swenson, Alan Z. Liu, F. Kamalabadi Mar 2005

Observational Investigations Of Gravity Wave Momentum Flux With Spectroscopic Imaging, J. Tang, G. R. Swenson, Alan Z. Liu, F. Kamalabadi

Physical Sciences - Daytona Beach

We apply a newly developed gravity wave momentum flux estimation method to the mesospheric measurements obtained with colocated airglow imager and meteor radar at Maui, Hawaii (20.7ºN, 156.3ºW), during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaign. The method identifies individual quasi-monochromatic gravity waves with periods between 6 and ~40 min, estimates the intrinsic wave parameters, and calculates the momentum fluxes carried by vertically propagating waves. Data taken on 28 October 2003 are analyzed in detail to reveal the relationship between momentum flux and wave parameters. The January, April, July, and October 2003 data are divided into summer and …


Book Review: The New Amateur Astronomer, T. D. Oswalt Mar 2005

Book Review: The New Amateur Astronomer, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The New Amateur Astronomer by Martin Mobberley. Springer, 2004 229p, 1852336633 $34.95


The Chromospheric Activity And Ages Of M Dwarf Stars In Wide Binary Systems, Nicole M. Silvesteri, T. D. Oswalt, Suzanne L. Hawley Feb 2005

The Chromospheric Activity And Ages Of M Dwarf Stars In Wide Binary Systems, Nicole M. Silvesteri, T. D. Oswalt, Suzanne L. Hawley

Publications

We investigate the relationship between age and chromospheric activity for 139 M dwarf stars in wide binary systems with white dwarf companions. The age of each system is determined from the cooling age of its white dwarf component. The current limit for activity-age relations found for M dwarfs in open clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for the exploration of this relationship at ages older than 4 Gyr. The general trend of stars remaining active for a longer time at later spectral type is confirmed. However, our larger sample and greater age …


The Dyad Theory Of Classical And Quantum Physics, Preston Jones Feb 2005

The Dyad Theory Of Classical And Quantum Physics, Preston Jones

Publications

The 4-space equations of hydrodynamics, electrodynamics, and quantum mechanics are developed using the dyad calculus. Gravity is found to couple hydrodynamics, electrodynamics, and quantum mechanics through the 4- space metric and differential operator. Expanding the 4-space equations of electrodynamics a time varying metric is shown to dissipate electromagnetic energy.


Climatology Of Short-Period Gravity Waves Observed Over Northern Australia During The Darwin Area Wave Experiment (Dawex) And Their Dominant Source Regions, P. -D. Pautet, M. J. Taylor, Alan Z. Liu, Gary Swenson Feb 2005

Climatology Of Short-Period Gravity Waves Observed Over Northern Australia During The Darwin Area Wave Experiment (Dawex) And Their Dominant Source Regions, P. -D. Pautet, M. J. Taylor, Alan Z. Liu, Gary Swenson

Physical Sciences - Daytona Beach

The Darwin Area Wave Experiment (DAWEX) was designed to investigate the generation and propagation of gravity waves from intense regions of localized convection that occur regularly over northern Australia (in the vicinity of Darwin) during the premonsoon period. This multinational program was conducted during the austral spring 2001 using a range of coordinated optical, radar, and in situ balloon measurements. As part of this program, all-sky image observations of short-period gravity wave events in the near infrared OH nightglow emission (altitude ~87 km) were made from two well-separated sites in northern Australia: Wyndham (15.5ºS, 128.1ºE) and Katherine (14.5ºS, 132.3ºE), over …


Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson Feb 2005

Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson

Physical Sciences - Daytona Beach

Characteristics of convective and dynamical instabilities in the mesopause region (between 85 and 100 km) over Maui, Hawaii (20.7ºN, 156.3ºW) are investigated using 19 nights, ~133 hours of high-resolution wind and temperature data obtained by the University of Illinois Na wind/temperature lidar during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaigns. The mean probabilities of convective and dynamical instabilities are observed to be ~3 and 10%, respectively, but there is considerable night-to-night variation. At any given time the probability that an unstable condition is found at some altitudes in the 85–100 km range is 90%. The Maui MALT data …


Comparison Of Meteor Radar And Na Doppler Lidar Measurements Of Winds In The Mesopause Region Above Maui, Hawaii, S. J. Franke, X. Chu, A. Z. Liu, W. K. Hocking Jan 2005

Comparison Of Meteor Radar And Na Doppler Lidar Measurements Of Winds In The Mesopause Region Above Maui, Hawaii, S. J. Franke, X. Chu, A. Z. Liu, W. K. Hocking

Physical Sciences - Daytona Beach

The coincident measurements span 96 hours and altitudes between 80 and 100 km. Statistical comparisons are carried out on radar/lidar winds with 1 hour and 4 km time and height resolution, respectively. The RMS radar/lidar wind component differences observed in this study are in the range 12–17 m/s at altitudes below 96 km. This is smaller than the RMS differences observed in a previous Na lidar and meteor radar comparison. Lidar wind component variances exceed radar variances, and radar/lidar covariance, is nearly equal to the radar variance. Excess variance observed by the lidar is consistent with the fact that the …


Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner Jan 2005

Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner

Physical Sciences - Daytona Beach

Vertical heat flux profiles induced by dissipating gravity waves in the mesopause region (85–100 km altitude) are derived from Na lidar measurements of winds and temperatures at Maui (20.7ºN, 156.3ºW), Hawaii, and compared with earlier results from Starfire Optical Range (SOR, 35.0ºN, 106.5ºW), New Mexico. The heat flux profile at SOR has a single downward maximum of 2.25 ± 0.3 K m/s at 88 km, while the profile at Maui has two downward maxima of 1.25 ± 0.5 K m/s and 1.40 ± 0.5 K m/s at 87 and 95 km, respectively. The common maximum below 90 km can be …


Maui Mesosphere And Lower Thermosphere (Maui Malt) Observations Of The Evolution Of Kelvin-Helmholtz Billows Formed Near 86 Km Altitude, J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. J. Rudy Jan 2005

Maui Mesosphere And Lower Thermosphere (Maui Malt) Observations Of The Evolution Of Kelvin-Helmholtz Billows Formed Near 86 Km Altitude, J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. J. Rudy

Physical Sciences - Daytona Beach

Small-scale (less than 15 km horizontal wavelength) structures known as ripples have been seen in OH airglow images for nearly 30 years. The structures have been attributed to either convective or dynamical instabilities; the latter are mainly due to large wind shears, while the former are produced by superadiabatic temperature gradients. Dynamical instabilities produce Kelvin-Helmholtz (KH) billows, which have been known for many years. However, models and laboratory experiments suggest that these billows often spawn a secondary instability that is convective in nature. While laboratory investigations see evidence of such structures, the evolution of these instabilities in the atmosphere has …


Robust Control Techniques For State Tracking In The Presence Of Variable Time Delays, Jarrett Goodell, Marc Compere, Miguel Simon, Wilford Smith, Ronnie Wright, Mark Brudnak Jan 2005

Robust Control Techniques For State Tracking In The Presence Of Variable Time Delays, Jarrett Goodell, Marc Compere, Miguel Simon, Wilford Smith, Ronnie Wright, Mark Brudnak

Publications

In this paper, a distributed driver-in-the-Ioop and hardware-in-the-Ioop simulator is described with a driver on a motion simulator at the U.S. Army TARDEC Ground Vehicle Simulation Laboratory (GVSL). Realistic power system response is achieved by linking the driver in the GVSL with a full-sized hybrid electric power system located 2,450 miles away at the TARDEC Power and Energy Systems Integration Laboratory (P&E SIL), which is developed and maintained by Science Applications International Corporation (SAIC). The goal is to close the loop between the GVSL and P&E SIL over the Internet to provide a realistic driving experience in addition to realistic …


A Full-Wave Investigation Of The Use Of A ‘‘Cancellation Factor’’ In Gravity Wave–Oh Airglow Interaction Studies, Michael P. Hickey Ph.D., Yonghui Yu Jan 2005

A Full-Wave Investigation Of The Use Of A ‘‘Cancellation Factor’’ In Gravity Wave–Oh Airglow Interaction Studies, Michael P. Hickey Ph.D., Yonghui Yu

Publications

Atmospheric gravity waves (GWs) perturb minor species involved in the chemical reactions of airglow emissions in the upper mesosphere and lower thermosphere. In order to determine gravity wave fluxes and the forcing effects of gravity waves on the mean state (which are proportional to the square of the wave amplitude), it is essential that the amplitude of airglow brightness fluctuation be related to the amplitude of major gas density fluctuation in a deterministic way. This has been achieved through detailed modeling combining gravity wave dynamics described using a full-wave model with the chemistry relevant to the airglow emission of interest. …