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Jones, C. E.

Publications and source records attributed to Jones, C. E..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Ω-slow Solutions and Be Star Disks

As the disk formation mechanism(s) in Be stars is(are) as yet unknown, we investigate the role of rapidly rotating radiation-driven winds in this process. We implemented the effects of high stellar rotation on m-CAK models accounting for the shape of the star, the oblate finite disk correction factor, and gravity darkening. For a fast rotating star, we obtain a two-component wind model, i.e., a fast, thin wind in the polar latitudes and an Ω-slow, dense wind in the equatorial regions. We use the equatorial mass densities to explore Hα emission profiles for the following scenarios: (1) a spherically symmetric star, (2) an oblate star with constant temperature, and (3) an oblate star with gravity darkening. One result of this work is that we have developed a novel method for solving the gravity-darkened, oblate m-CAK equation of motion. Furthermore, from our modeling we find that (a) the oblate finite disk correction factor, for the scenario considering the gravity darkening, can vary by at least a factor of two between the equatorial and polar directions, influencing the velocity profile and mass-loss rate accordingly, (b) the Hα profiles predicted by our model are in agreement with those predicted by a standard power-law model for following values of the line-force parameters: 1.5≲k≲3,α∼0.6, and δ≳0.1, and (c) the contribution of the fast wind component to the Hα emission line profile is negligible; therefore, the line profiles arise mainly from the equatorial disks of Be stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

The Disk Physical Conditions of 48 Persei Constrained by Contemporaneous Hα Spectroscopy and Interferometry

We utilize a multi-step modeling process to produce synthetic interferometric and spectroscopic observables, which are then compared to their observed counterparts. Our extensive set of interferometric observations of the Be star 48 Per, totaling 291 data points, were obtained at the Navy Precision Optical Interferometer from 2006 November 07 to 23. Our models were further constrained by comparison with contemporaneous Hα line spectroscopy obtained at the John S. Hall Telescope at the Lowell Observatory on 2006 November 1. Theoretical spectral energy distributions, SEDs, for 48 Per were confirmed by comparison with observations over a wavelength regime of 0.4–60 μm from Touhami et al. and Vieira et al. Our best-fitting combined model from Hα spectroscopy, Hα interferometry, and SED fitting has a power-law density fall off, n, of 2.3 and an initial density at the stellar surface of ρ{sub 0}=1.0×10{sup −11} g cm{sup −3} with an inclination constrained by Hα spectroscopy and interferometry of 45{sup ∘}±5{sup ∘}. The position angle for the system, measured east from north, is 114° ± 18°. Our best-fit model shows that the disk emission originates in a moderately large disk with a radius of 25 R {sub *}, which is consistent with a disk mass of approximately 5 × 10{sup 24} g or 3 × 10{sup −10} M {sub *}. Finally, we compare our results with previous studies of 48 Per by Quirrenbach et al. and find agreement, whereas our disk size does not agree with Delaa et al., based on a much smaller visibility set.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Evidence for Different Disk Mass Distributions between Early- and Late-type Be Stars in the BeSOS Survey

The circumstellar disk density distributions for a sample of 63 Be southern stars from the BeSOS survey were found by modeling their H α emission line profiles. These disk densities were used to compute disk masses and disk angular momenta for the sample. Average values for the disk mass are 3.4 × 10{sup −9} and 9.5 × 10{sup −10} M {sub ⋆} for early (B0–B3) and late (B4–B9) spectral types, respectively. We also find that the range of disk angular momentum relative to the star is (150–200) J {sub ⋆}/ M {sub ⋆} and (100–150) J {sub ⋆}/ M {sub ⋆}, again for early- and late-type Be stars, respectively. The distributions of the disk mass and disk angular momentum are different between early- and late-type Be stars at a 1% level of significance. Finally, we construct the disk mass distribution for the BeSOS sample as a function of spectral type and compare it to the predictions of stellar evolutionary models with rapid rotation. The observed disk masses are typically larger than the theoretical predictions, although the observed spread in disk masses is typically large.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2013

Modeling Circumstellar Disks of B-Type Stars with Observations from the Palomar Testbed Interferometer

Geometrical (uniform disk) and numerical models were calculated for a set of B-emission (Be) stars observed with the Palomar Testbed Interferometer (PTI). Physical extents have been estimated for the disks of a total of15 stars via uniform disk models. Our numerical non-LTE models used parameters for the B0, B2, B5, and B8spectral classes and following the framework laid by previous studies, we have compared them to infrared K-band interferometric observations taken at PTI. This is the first time such an extensive set of Be stars observed with long-baseline interferometry has been analyzed with self-consistent non-LTE numerical disk models.

Grzenia, B. J.↗
NASA NTRS1979

User's guide: SPAR processor MN analysis of inelastic three-dimensional solids, part 2

A user's guide to the processor MN is presented. The processor MN is used to analyze systems in which some or all of the three dimensional elements have nonlinear stress-strain relations. Representations of nonlinear material behavior implemented into the system are provided including Von Mises yield criterion, the Prandtl-Reuss flow rule, and the mechanical sublayer method. The primary data sets used to represent the state of the system are presented.

Whetstone, W. D.↗
NASA NTRS1975

STDN ranging equipment

Final results of the Spaceflight Tracking and Data Network (STDN) Ranging Equipment program are summarized. Basic design concepts and final design approaches are described. Theoretical analyses which define requirements and support the design approaches are presented. Design verification criteria are delineated and verification test results are specified.

Jones, C. E.↗
NASA NTRS1973

Temperature, stress, and annealing effects on the luminescence from electron-irradiated silicon

Low-temperature photoluminescence spectra are presented for Si crystals which have been irradiated with high-energy electrons. Studies of isochronal annealing, stress effects, and the temperature dependences of the luminescence are used to discuss the nature of the luminescent transitions and the properties of defects. Two dominant bands present after room-temperature anneal of irradiated material are discussed, and correlations of the properties of these bands are made with known Si defects. A band between 0.8 and 1.0 eV has properties which are related to those of the divacancy, and a band between 0.6 and 0.8 eV has properties related to those of the Si-G15(K) center. Additional peaks appear in the luminescence after high-temperature anneal; the influence of impurities and the effects of annealing of these lines are discussed.

Jones, C. E.↗
NASA NTRS1972

Snap dynamics

Computer program calculates normal vibration modes of complex structures elimating excessively large amounts of input data, run time, and core storage. Provision for accuracy improvement is also included.

Kiefling, L.↗
NASA NTRS1972

Study of propellant dynamics in a shuttle type launch vehicle

A method and an associated digital computer program for evaluating the vibrational characteristics of large liquid-filled rigid wall tanks of general shape are presented. A solution procedure was developed in which slosh modes and frequencies are computed for systems mathematically modeled as assemblages of liquid finite elements. To retain sparsity in the assembled system mass and stiffness matrices, a compressible liquid element formulation was incorporated in the program. The approach taken in the liquid finite element formulation is compatible with triangular and quadrilateral structural finite elements so that the analysis of liquid motion can be coupled with flexible tank wall motion at some future time. The liquid element repertoire developed during the course of this study consists of a two-dimensional triangular element and a three-dimensional tetrahedral element.

Jones, C. E.↗
NASA NTRS1971

Substructuring techniques

The substructure function generator program is discussed. Input to this program consists of a definition of a finite element model of a substructure, and specification of the type and number of displacement functions to be generated. Primary output is a substructure data file containing the substructure mass and stiffness matrices expressing kinetic and potential energies as quadratic forms in coefficients of the displacement functions, etc. The substructure synthesis program forms complete system mass, stiffness, and damping matrices, computes system modes and frequencies, and executes transient response calculations. Input to this program consists of the array of substructure data files generated by the function generator program for individual substructures, and data cards defining the position and interconnection of the substructures, damping data, forcing function details, and function control parameters.

Whetstone, W. D.↗
NASA NTRS1971

Advanced substructuring techniques

Computer programs for evaluating vibrational characteristics of complicated structural systems mathematically modeled as assemblages of arbitrary substructures

Jones, C. E.↗
NASA NTRS1971

Recombination luminescence in irradiated silicon-effects of uniaxial stress and temperature variations.

Demonstration that luminescence in irradiated silicon consists of a spectral group between 0.80 and 1.0 eV which seems to be independent of impurities, while a lower energy group between 0.60 and 0.80 eV is seen only in pulled crystals. The small halfwidth and temperature dependence of the sharp zero-phonon lines observed in these spectra indicate that the luminescence arises from a bound-to-bound transition. A model is proposed for the transition mechanism. Stress data taken on the 0.79-eV zero-phonon line in pulled crystals can be fit by either a tetragonal 100 (in brackets) defect symmetry or by conduction-band splitting effects. It is suggested that the 0.79-eV zero-phonon line and the 0.60- to 0.80-eV spectral group arise from the EPR G-15 center. Stress data on a zero-phonon line at 0.97 eV associated with the 0.80- to 1.0-eV spectral group can be explained by a trigonal 111 (in brackets) defect. The divacancy is tentatively suggested as responsible for this luminescence spectra.

Jones, C. E.↗