Calculated Line Profiles Research Articles

Non-local thermodynamic equilibrium line profiles, rotation, and magnetic fields in seven DA white dwarfs

view Abstract Citations (32) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Non--Local Thermodynamic Equilibrium Line Profiles, Rotation, and Magnetic Fields in Seven DA White Dwarfs Koester, D. ; Herrero, A. Abstract Non-LTE calculations of H-alpha line profiles are presented and applied to derive rotational velocities from high-resolution spectra of DA white dwarfs. This paper extends recent work by Pilachowski and Milkey (1984, 1987) to southern hemisphere objects and confirms their findings that all white dwarfs seem to be slow rotators. Of the seven objects in this study only one has v sin 1 = 30 + or - 20 km/s, only marginally different from 0. The remaining objects are all fitted by v sin 1 = 0, and upper limits of 20-40 km/s were obtained. Upper limits on magnetic fields of 25,000 G were determined for all objects from the absence of Zeeman splitting. Publication: The Astrophysical Journal Pub Date: September 1988 DOI: 10.1086/166700 Bibcode: 1988ApJ...332..910K Keywords: Balmer Series; Line Spectra; Stellar Magnetic Fields; Stellar Rotation; Thermodynamic Equilibrium; White Dwarf Stars; Angular Velocity; High Resolution; Southern Hemisphere; Zeeman Effect; Astrophysics; LINE PROFILES; STARS: MAGNETIC; STARS: ROTATION; STARS: WHITE DWARFS full text sources ADS | data products SIMBAD (8)

Field-dependent dipole matrix elements and their application to the calculation of plasma-broadened line profiles

We have computed field-dependent wavefunctions and dipole matrix elements for hydrogenic ions in the presence of a uniform electric field; we present the results for transitions connecting the ground and excited states. As an application we use these elements to compute Stark-broadened static line profiles and compare with similar ones that use field-independent matrix elements. The line-shape sensitivity to the use of field-dependent matrix elements is discussed.

The magnetic field and abundance distribution geometry of the peculiar A star 53 Camelopardalis

view Abstract Citations (215) References (76) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Magnetic Field and Abundance Distribution Geometry of the Peculiar A Star 53 Camelopardalis Landstreet, J. D. Abstract New spectra have been obtained of the magnetic Ap star 53 Cam, well spaced through its 8.03 day rotation period, covering the spectral regions λλ3900 - 3960 and 4250 - 4315. These data, and previously obtained Hβ Zeeman analyzer observations of the longitudinal field strength, have been used to derive models of the magnetic field geometry and the abundance distributions of Ca, Cr, Fe, Sr, and Ti. The models have been obtained by use of a new line synthesis program that incorporates the effects of an assumed magnetic field and abundance distribution into the calculation of line profiles. Calculated profiles are compared with observations. The model is used to derive a radius of R/R_sun; = 2.3±0.4, a luminosity of log L/L_sun; = 1.4±0.17, and a mass of M/M_sun; = 2.0±0.3 for 53 Cam. Publication: The Astrophysical Journal Pub Date: March 1988 DOI: 10.1086/166155 Bibcode: 1988ApJ...326..967L Keywords: A Stars; Abundance; Interstellar Magnetic Fields; Line Shape; Magnetic Stars; Peculiar Stars; B Stars; H Beta Line; Line Of Sight; Stellar Spectra; Zeeman Effect; Astrophysics full text sources ADS | data products SIMBAD (3)

Hydrogen Balmer alpha intensity distributions and line profiles from multiple scattering theory using realistic geocoronal models

The H Balmer α nightglow is investigated by using Monte Carlo models of asymmetric geocoronal atomic hydrogen distributions as input to a radiative transfer model of solar Lyman β radiation in the thermosphere and exosphere. The radiative transfer model includes all orders of scattering, temperature variation with altitude and solar zenith angle, and anisotropic velocity distributions. The influences of multiple scattering of Lyman β radiation and of observing geometry on the H Balmer α intensity and effective temperature are evaluated in detail. Morning and evening hydrogen distributions for minimum, medium, and maximum solar activity are used in calculations of nightglow emission rates and line profiles. For each of the hydrogen models the H Balmer α intensity and effective temperature are displayed as a function of solar depression angle, observation zenith angle, and azimuth relative to the sun, to make possible detailed comparison to observations. Except for rather unique observing conditions, multiple scattering effects cannot be ignored for the determination of either intensity or temperature. Observed effective temperatures which are significantly less than the exobase temperature may be due either to low‐altitude thermospheric hydrogen or to high‐altitude exospheric hydrogen and depend on the observing conditions and the level of solar activity. Previous (selected) observations of the H Balmer α nightglow and effective temperatures are compared to models which most closely represent the solar conditions of the observations. Results of the theoretical investigation of H Balmer α emissions and of model‐data comparisons indicate that predicted morning‐evening concentration variations yield small intensity variations for solar depression angles greater than 20°. The variations with solar depression angle of observed intensities and temperatures both show discrepancies in comparison with model results. A substantial disagreement occurs in absolute intensity: the long‐standing result that the observations are a factor of 2 higher than model results is reaffirmed with recent observational data and improved estimates of the solar H Lyman β flux. Observing schemes are discussed which lead to first approximations to hydrogen content independent of solar flux and to the high‐altitude atomic hydrogen distribution.

Influence of the glass-to-plasma boundary layers in a T-tube on the H β line profile

We have used a simple glass-to-plasma boundary layer ( bl) model to evaluate the influence of bls on measured H β line profiles emitted from a T-tube hydrogen plasma. Calculations were performed for a wide range of electron densities and temperatures. The results show that the calculated line profiles for temperatures of 3 × 10 4 K and higher are significantly wider than they would be if the bls were absent. At the most frequently encountered temperatures of the T-tube plasmas (∽2 × 10 4 K), the calculated profiles influenced by bls resemble theoretical profiles. No significant influence of the bls on the H β central part was found, except when the optical thickness of the whole plasma becomes significant.

Theoretical line profiles from a symbiotic system

A model for a symbiotic system is presented which is not spherically symmetrical. The system consists of a cool, mass losing giant and a hot star. The stellar wind from the cool star is radiatively ionized by the hot companion, and the resulting nebular lines are emitted mainly close to the cool star. Due to the elliptical orbit, the line fluxes change with time because of the varying separation of the stars. The line profiles vary from symmetrical to asymmetrical, depending on the angle between the line of sight and the axis of symmetry. The calculated line profiles are compared with observed UV lines of the symbiotic star HBV 475.

The 'SEI' method for accurate and efficient calculations of line profiles in spherically symmetric stellar winds

The 'SEI' method for accurate and efficient calculations of line profiles in spherically symmetric stellar winds

Mass Transfer and Line Profiles - WZ Sge

AbstractThe calculation of a gas stream offers two modes of the stream. In any case the stream cannot be detected optically. The calculated line profiles caused by the disc are demonstrated.

Theoretical Line Profiles from a Symbiotic System

AbstractA model for a symbiotic system is presented which is not spherically symmetrical. The system consists of a cool, mass losing giant and a hot star. The stellar wind from the cool star is radiatively ionized by the hot companion, and the resulting nebular lines are emitted mainly close to the cool star. Due to the elliptical orbit, the line fluxes change with time because of the varying separation of the stars. The line profiles vary from symmetrical to asymmetrical, depending on the angle between the line of sight and the axis of symmetry. The calculated line profiles are compared with observed UV lines of the symbiotic star HBV 475.

A method for calculation of line profiles in expanding atmospheres: Application to winds from central stars of planetary nebulae

The structure of a stellar wind and its associated mass loss can be derived from the analysis of ñ Cygni-like line profiles. These do better occur in the UV range and have been extensively observed with the Copernicus (900–1450 A) and IUE Satellites (1150–3200 A).

Cloud models for the nuclei of active galaxies - A distribution function description

view Abstract Citations (12) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Cloud Models for the Nuclei of Active Galaxies: A Distribution Function Description Whittle, Mark ; Saslaw, William C. Abstract An analytic method is derived for calculating the distribution function of cloud properties in any region of an active galactic nucleus from the evolution of individual clouds along their trajectories. A simple model containing supersonic clouds confined by ram pressure illustrates the distribution function method and its effect on calculated line profiles. In developing this model, attention is drawn to a thermomechanical imbalance which can be important for clouds whose mechanical equilibrium is set by ram pressure balance, but whose thermal equilibrium is set by a central ionizing source. This imbalance can occur along some trajectories and may result in cloud destruction. The implications of cloud distribution functions and cloud destruction processes on the evaluation of realistic line profiles are discussed. Publication: The Astrophysical Journal Pub Date: November 1986 DOI: 10.1086/164668 Bibcode: 1986ApJ...310..104W Keywords: Active Galaxies; Astronomical Models; Galactic Nuclei; Interstellar Gas; Molecular Clouds; Active Galactic Nuclei; Differential Equations; Distribution Functions; H Beta Line; Seyfert Galaxies; Trajectory Analysis; Astrophysics; GALAXIES: INTERNAL MOTIONS; GALAXIES: NUCLEI; GALAXIES: SEYFERT full text sources ADS |

Mass Loss from Cool Stars

Recently obtained spectroscopic observations indicating mass loss in cool stars are reviewed with analogies to the solar atmosphere. Spectral diagnostics of mass loss are discussed with new theoretical calculations of chromospheric line profiles. A general picture of mass loss from cool stars is developed and related to chromospheric and coronal emissions measured by IUE and the HEAO-2 Obgervatory. These winds range in characteristics from the hot (106 K) and fast wind with low mass loss found in the dwarf stars to the warm (~ 10-5 K), moderate speed winds present in hybrid luminous supergiants, and the coolest massive winds emerging from the latest type supergiants exhibiting lowest thermal velocities and circumstellar shells. Evidence for stellar surface inhomogeneity and variability of outflow is briefly discussed.

Calculation of diffraction line profiles in the case of coupled stacking fault and size-effect broadening: application to boehmite AlOOH

A method that allows the calculation of the profile of the whole X-ray diffraction pattern of a powder, taking into account simultaneously a size-effect broadening and the influence of a stacking fault in a layered structure is described. A model of a stacking fault has been chosen as a function of experimental data recorded with gels or divided powders of boehmite AlOOH. By means of profile refinements, an amplitude and a fault probability have been deduced and correlated with the presence of non-stoichiometric excess water. The procedure can be generalized to the same faulting mechanism in other materials or to other types of fault.

Asymmetry of Stark-broadened Lyman lines from laser-produced plasmas

Three significant causes of spectral line asymmetry: the ion-quadrupole interaction, the quadratic Stark effect, and fine-structure splitting, are included in the calculation of Lyman line profiles emitted by highly ionized hydrogenic radiators in a dense, hot plasma. The line asymmetries are shown to be strongly dependent on the plasma density, indicating that the asymmetry may be of use as a density diagnostic. This work was supported by Lawrence Livermore National Laboratory under sub-contract ♯5962705.

Calculation of diffraction line profiles in the case of a major size effect: application to boehmite A1OOH

A method allowing the calculation of the diffraction line profiles of a powder, whose crystallites are convex polyhedrons, is described. The decomposition of the crystallite volume into elementary prisms distinguishes three cases. The analytical expression of the results allows their derivation in the case of a linear size distribution. With instrumental broadening causes taken into account, an application of this method is given in restoring the whole X-ray diffraction pattern of samples of finely divided powders of boehmite, AlOOH.

Observational diagnostics for models of magnetic flux tubes

view Abstract Citations (18) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observational diagnostics for models of magnetic flux tubes Ribes, E. ; Rees, D. E. ; Cheng, F. Abstract Dynamic models of flux tubes were used to interpret the presence of mass motions with large velocity gradients associated with spatially unresolved magnetic elements in the solar photosphere. A downflow was necessary in order to concentrate the magnetic field and provide a heating mechanism to brighten the flux tubes. There are two types of steady flow models: one has a moderate field strength (less than 1 kG) and a downflow decelerating with increasing depth and the second has a strong field and a downflow accelerating with increasing depth. To distinguish between these two field strengths, observed line profiles were compared to calculated line profiles. The comparison revealed that the main properties of the intensity line profiles and asymmetries of Stokes V-profiles was best explained by magnetic elements with moderate field strength. Further study is necessary to determine the reason for the redshift of the V-zero crossing point. Publication: The Astrophysical Journal Pub Date: September 1985 DOI: 10.1086/163444 Bibcode: 1985ApJ...296..268R Keywords: Circular Polarization; Magnetic Flux; Magnetohydrodynamics; Photosphere; Solar Magnetic Field; Stokes Law Of Radiation; Bernoulli Theorem; Steady Flow; Thermodynamic Properties; Zeeman Effect; Solar Physics full text sources ADS |

Non-adiabatic effects in collision-induced radiative transitions

Perturbation theory for the interaction of light with a binary collisional system is applied to the calculation of line profiles, spontaneous emission rates and absorption or stimulated emission coefficients. For the usual radiation fields are perturber densities, this approximation is valid at all detunings Delta omega except the very narrow resonance region. Appropriate expansions of the total binary system wavefunctions give the emission and absorption profiles or rates, for atom-electron systems as well as for atom-atom systems, from the impact regime at small Delta omega up to the Born-Oppenheimer regime at very large Delta omega in collision-induced radiative transitions, the transitions being asymptotically allowed or forbidden. Emphasis is given to the proper averages and sums over initial and final states of the binary system which give rise to non-adiabatic effects. One shows that it is of crucial importance to include all dynamical effects during one collisional event before undertaking any calculation at small Delta omega where simultaneous collisions may occur.

Full Coulomb calculation of Stark broadening in laser-produced plasmas

The full Coulomb interaction between radiating ions and perturbing electrons is included in the calculation of Lyman-series spectral line profiles emitted by highly ionized hydrogenic radiators in a dense, hot plasma. Profiles from this calculation and from a similar calculation based on the dipole approximation for the radiator-perturber interaction are compared over a range of plasma densities. The significance of inelastic collisions between the radiator and perturbing electrons is also examined.

Influence of Lyman-series fine-structure opacity on theK-shell spectrum and level populations of low-to-medium-Zplasmas

As laboratory plasmas of increasing atomic number, temperature, size, and/or density are produced, it becomes likely that the details of the doublet opacity profiles of the Lyman series will influence the $K$-shell level populations and spectrum. Accordingly, we have analyzed these effects for a range of plasma parameters, confined to densities low enough for Stark broadening to be unimportant. An analytic model is developed which predicts line power enhancements and level-population changes for $K$-shell plasmas. This model is based upon photon escape probability and collisional quenching concepts and is valid for plasmas of atomic number \ensuremath{\sim}13-26. Additionally, an extensive set of numerical calculations of line ratios, line profiles, and level populations has been carried out for $K$-shell argon plasmas. Each computation was performed both with detailed fine-structure opacity profiles and with a single-Voigt-profile approximation. The results of these calculations may be scaled for plasmas of atomic number other than 18 using a simple set of rules discussed in the text.

Ray Tracing of a Concave-Curved-Crystal Spectrometer and Its Detailed Characteristics for X-Ray Spectroscopic Diagnostics of High-Temperature Plasmas

A method of ray tracing is presented for a spectrometer with a concave-curved crystal to be used for X-ray spectroscopic diagnostics of high-temperature plasmas. Calculations have been carried out for an LiF(200) crystal with a lowland circle of radius 50 cm and a Gaussian rocking curve. With a linear X-ray source, the most suitable parameters of the spectrometer were accurately determined by use of the ray tracing, and the characteristics were investigated in detail. The ray tracing was also applied to a point source of X-rays, and the best conditions for geometric relations between the point source and the spectrometer were found. The spectral distortion is also described here analytically. The calculated line profile including the natural broadening of the X-ray source is compared with the experimental result for FeKα1. Good agreement is obtained.