Author name code: elste ADS astronomy entries on 2022-09-14 author:"Elste, Guenther" ------------------------------------------------------------------------ Title: Limb Darkening Measurements Free of Instrumental Stray Light Authors: Elste, G.; Gilliam, L. Bibcode: 2007SoPh..240....9E Altcode: We have used the 40 cm coronagraph with an inverse occulting disk to observe the limb darkening free of instrumental stray light. Our results agree remarkably well with those of Petro et al. (1984, Astrophys. J.283, 426) who used the McMath - Pierce tower telescope but employed a different correction procedure for instrumental stray light than Neckel and Labs (1994, Solar Phys.153, 91), whose results for λ=445.1 nm deviate systematically, apparently overcorrecting for stray light. Future continuation of such highly reproducible measurements offers an interesting independent diagnostic of possible slow trends in effective temperature (Teff) and in total solar irradiance. Title: Coffee breaks in Ann Arbor Authors: Elste, Guenther H. Bibcode: 1998ASSL..222...43E Altcode: 1998ream.conf...43E No abstract at ADS Title: Fine-Resolution Imaging of Solar Features using Phase-Diverse Speckle Authors: Paxman, R. G.; Seldin, J. H.; Elste, G. H. Bibcode: 1995SPD....26..201P Altcode: 1995BAAS...27..950P No abstract at ADS Title: Solar Granulation Restoration using Phase-Diverse Speckle Imaging: Verification via Simulations and Measurements Authors: Seldin, J. H.; Paxman, R. G.; Elste, G. H. Bibcode: 1995SPD....26..502S Altcode: 1995BAAS...27..956S No abstract at ADS Title: Line Shapes of Rotating Stars with Application to Alpha Lyrae Authors: Elste, G. H. Bibcode: 1992ApJ...384..284E Altcode: Profiles of weak and medium strong lines in the high-resolution spectrum of Vega can in principle be understood by the center-to-limb variation of their equivalent widths, predicted by a standard model atmosphere. Finer details may require a different model structure depending on the latitude of the rotating star, and perhaps differential rotation. Title: Asymmetries in Limb Darkening Reanalyzed Authors: Elste, G. H. Bibcode: 1990SoPh..126...37E Altcode: The cause of the asymmetries in limb darkening reported by Neckel and Labs (1987) is discussed on the basis of new, stray-light-free observations, and found to be of instrumental origin. Title: Limb Darkening Variations Authors: Elste, G. Bibcode: 1988srov.proc..204E Altcode: No abstract at ADS Title: Manganese and carbon lines as temperature indicators. Authors: Elste, G. Bibcode: 1986SoPh..107...47E Altcode: 1987SoPh..107...47E Selected hyperfine structure broadened lines of various excitations and the carbon line at 5380 Å are tested as temperature diagnostics for photospheric heterogeneities. This is done by comparing the observed center-to-limb variation of the equivalent widths of these lines with predictions by several proposed models of homogeneous type. Model 10 (Elste, 1968), which also explains the limb-darkening of the continuum in the same spectral range, provides a better basis for the analysis of heterogeneities at different photospheric levels than other recent reference models. Title: Temperature Gradients in Regions with and Without Magnetic Fields Authors: Elste, G. Bibcode: 1985tphr.conf..185E Altcode: No abstract at ADS Title: Temperature Gradients in the Solar Granulation Authors: Elste, G. Bibcode: 1985LNP...233..169E Altcode: 1985hrsp.proc..169E Profiles of the C 5380 and the Mn 5395 recorded using two CCDs in the focal plane of the Echelle grating spectrograph of the Vacuum Tower at Sacramento Peak Observatory are analyzed. The behavior of the C 5380 and the Mn 5395 with increasing resolution is studied and compared to the photographic spectra of Edmonds et al. (1965); the relation between continuum and line strength is investigated. It is observed that: the continuum intensity and carbon line equivalent width are positively correlated with the Edmonds et al. data for C 5052 and continuum; the carbon lines originate in the same deep layer as the continuum and become stronger with increasing temperatures; and the manganese line weakens with increasing temperatures and displays a positive correlation with the continuum intensity. The data reveal that temperature gradients are steeper in regions with higher temperatures in deep layers and flatter in regions with lower temperatures in deep layers. The spatial distribution of the varying temperature gradients is examined. Title: Temperature gradients in regions with and without magnetic fields. Authors: Elste, G. Bibcode: 1985MPARp.212..185E Altcode: Observational evidence for the flattening of the temperature gradients in the deep photosphere by magnetic flux tubes is derived from the equivalent widths of the high excitation carbon line at 5380 Å and a ground level manganese line at 5395 Å, which also serves as an indicator for the presence of longitudinal magnetic fields. Title: On the Sun's Limb Brightening in the Visible Authors: Elste, G. H. Bibcode: 1984SoPh...93...15E Altcode: It is shown that in practice the method by Julius (1906) is incapable to determine the limb intensity drop. The brief intensity reversal near the extreme limb as derived from cinematography of flash spectra can be explained by diffraction. Title: Book-Review - Stellar Turbulence Authors: Gray, D. F.; Linsky, J. L.; Elste, G. H. Bibcode: 1983ApL....23..174G Altcode: No abstract at ADS Title: Characterististics of plage fragments with photospheric network properties Authors: Nauer, D. J.; Teske, R. G.; Elste, G. E. Bibcode: 1980SoPh...67...23N Altcode: Using data taken with the multi-channel magnetograph at KPNO, we demonstrate that plage regions surrounding a sunspot have thermal properties found in the photospheric network. These network-like regions existed up to the edge of the penumbra of the sunspot. Temperature gradients inferred from equivalent width fluctuations in our data do not conflict with the requirements of the theory (Parker, 1978) for flux tubes to exist at subphotospheric levels. Title: Dependence of the correlation of small scale photospheric structures upon resolution. Authors: Teske, R. G.; Elste, G. H. Bibcode: 1979SoPh...62..241T Altcode: Correlations between continuum intensity, velocity, and equivalent widths of two Mn I lines as observed with two different entrance apertures tend to deteriorate with improvement in spatial resolution. The KPNO multichannel magnetograph was used to make area scans at the center of the disk with entrance apertures 3.5″×2.5″ arc and 1″×1″ arc. A coherence analysis shows that this effect is caused by marked differences of fluctuations in temperature and temperature gradients as well as in the velocity structure of photospheric elements of various sizes. Title: Photospheric network from study of manganese lines. Authors: Elste, G.; Teske, R. G. Bibcode: 1978SoPh...59..275E Altcode: Area scans with the multi-channel magnetograph at the Kitt Peak McMath Telescope provided simultaneous measures of equivalent widths in two Mn lines, continuum intensity and longitudinal magnetic field component. Observations were carried out with apertures of 2.5″ × 3.5″ arc and 1″ × 1″ arc. For the network elements, which were identified using the magnetic field as tracer, we developed relationships betweenIContinuum,WλVDoppler and longitudinal field strength. With a minimum of assumptions it is possible to write from these observed relations an expression connecting true temperature perturbation in the line forming layers of the network to true longitudinal field strength. The results provide some constraints upon possible network models. Title: Vanadium abundances in early A stars. Authors: Cowley, C. R.; Elste, G. H.; Urbanski, J. L. Bibcode: 1978PASP...90..536C Altcode: Vanadium-to-hydrogen ratios have been determined for Omicron Peg, HR 6127, HR 465 (rare-earth minimum), and HR 8216. With respect to the solar system, vanadium is overabundant in the first two stars, possibly normal in the third, and underabundant in the fourth. The range in the V/H ratio in these four stars is between one and two orders of magnitude. An intercomparison of the four spectra shows that the strong V II lines occur in the stars with weaker Cr and Fe spectra. The vanadium anomaly is thus suggestive of the well-known calcium anomaly in peculiar A stars, but the vanadium and calcium abundances are not believed to be closely correlated. Title: Reliable of Equivalent Width Determinations or how much can we Trust Published Data? Authors: Elste, G. Bibcode: 1978hrs..conf..692E Altcode: No abstract at ADS Title: Hydrogen Lines in the Solar Atmosphere Authors: Elste, G. Bibcode: 1975BAAS....7..366E Altcode: No abstract at ADS Title: Balmer Lines and the Harvard - Smithsonian Reference Atmosphere. Authors: Elste, G.; Hartoog, M. Bibcode: 1973BAAS....5...20E Altcode: No abstract at ADS Title: Inhomogeneous photospheres. Authors: Elste, G. Bibcode: 1972BAAS....4..424E Altcode: No abstract at ADS Title: Microturbulence in Main Sequence A and F Stars. Authors: Elste, G.; Ionson, J. Bibcode: 1971BAAS....3..380E Altcode: No abstract at ADS Title: Line broadening in gamma Equulei. Authors: Evans, J. C.; Elste, G. Bibcode: 1971A&A....12..428E Altcode: Weak and medium strong iron lines in y Equ have been used to show that velocities of 3 km/s exist in the photosphere. The proffles of the sharpest lines, which are more triangniar than bell-shaped, and the curve-of- growth indicate ouly small effects from microturbulence, the major influences on the proffle are macroturbulence and rotation. As can be expected for a magnetic star most lines are broadened by unresolved Zeeman patterns. This is concluded from a comparison of observed with theoretical line proffles formed in an LTE model atmosphere (0vff = 0.654, log g = 3.5, solar abundances) under the presence of a transverse Zeeman effect for field strengths in excess of 2000 Gauss. Although it is possible to recognize Zeeman broadening as distinct from other broadening mechanisms it may be physically unrealistic to expect a unique field strength for all sorts of lines in the spectrum. Key words: line broadening - stellar magnetic fields - Ap star Title: Effects of Penumbral Radiation on Physical Conditions in the Umbra of Sun Spots. Authors: Fullerton, W.; Elste, G. Bibcode: 1971BAAS....3..247F Altcode: No abstract at ADS Title: The Ionization of Atoms in the Umbra by the Radiation Field of the Penumbra Authors: Fullerton, Wayne; Elste, Günther Bibcode: 1970BAAS....2R.193F Altcode: No abstract at ADS Title: Astrophysical Damping Constants for Neutral Iron Authors: Cowley, Charles R.; Elste, Guenther H.; Allen, Robert H. Bibcode: 1969ApJ...158.1177C Altcode: Empirical damping constants are derived for twenty-six lines of neutral iron by using the solar spec- trum. Eight of these lines have also been measured by Kusch, and the agreement between the two sets of measurements is satisfactory. We suggest that these damping constants may be used to obtain abundances and to strengthen spec- troscopic determinations of surface gravity Title: Excitation Temperatures of Fe I in the Sun and A Stars and Systematic Errors in the gf Scale Authors: Elste, Guenther Bibcode: 1969BAAS....1R.340E Altcode: No abstract at ADS Title: Comments on the Bilderberg Continuum Atmosphere Authors: Elste, Günther Bibcode: 1968SoPh....3..106E Altcode: The Bilderberg Continuum Atmosphere fails to reproduce the observed limb-darkening throughout the range of wavelengths 4500 Å<λ< 25 000 Å. The temperature-pressure diagram for the deep layers of this model is a curve which is flatter than the relation predicted from the mixing length theory. A modification of the Bilderberg Continuum Atmosphere that improves representation of the observations and theoretical results is proposed. Title: The Distinction Between - and Macroturbulence in the Solar Photosphere Using Line Profiles Authors: Elste, Guenther H. E. Bibcode: 1967ApJ...148..857E Altcode: On the basis of line-profile studies of sixty-two weak and medium-strong lines of Fe I, whose excitation potentials lie above 3 eV, a distinction between macro- and microturbulence is sought by comparing the observed relation between the half-widths and the equivalent widths with model computations. The shape of the lines near their cores as well as the curves of growth supports the result that the microturbulence velocity must be as low as 1 km/sec, while macroturbulent velocities of at least 1.5 km/sec are needed to explain the observations These conclusions are drawn from spectra of the center of the disk only. The more extensive study of the velocity field using the complete center-to4imb variation of the line profiles is in progress. Title: An atmsphere analysis of the magnetic star Gamma Equulei Authors: Evans, J. C.; Elste, G. Bibcode: 1967AJ.....72S.298E Altcode: No abstract at ADS Title: Direct observational evidence for a small value of the turbulence in sunspot umbrae Authors: Elste, G. Bibcode: 1963JQSRT...3..185E Altcode: No abstract at ADS Title: Difficulties in the explanation of the wings of the Balmer lines in sunspot umbrae Authors: Elste, G. Bibcode: 1963JQSRT...3..187E Altcode: No abstract at ADS Title: Der Einfluβ von Streulicht auf die Photometrie der Sonnenoberfläche. Mit 4 Textabbildungen Authors: David, K. H.; Elste, G. Bibcode: 1962ZA.....54...12D Altcode: No abstract at ADS Title: Die Mitte-Rand-Variation schwacher bis mittelstarker Fraunhoferlinien auf der Sonnenscheibe Authors: Elste, Günther Bibcode: 1960VeGoe...6..287E Altcode: No abstract at ADS Title: The centre-limb-variation of weak and moderately strong Fraunhofer lines on the solar disc (Die Mitte-Rand-Variation schwacher bis mittelstarker Fraunhoferlinien auf der Sonnenscheibe) Authors: Elste, Günther Bibcode: 1960VeGoe...6..285E Altcode: No abstract at ADS Title: Temperatur und Turbulenz in ruhenden Protuberanzen, bestimmt aus Linien-Breiten Authors: ten Bruggencate, Paul; Elste, Günther Bibcode: 1959VeGoe...7..257T Altcode: in English precedes German text Title: Die Entzerrung von Spektrallinien unter Verwendung von Voigtfunktionen Authors: Elste, Günther Bibcode: 1958VeGoe...6..157E Altcode: No abstract at ADS Title: Atmospheres of the B Stars.IV. The Calculation of Partition Functions. Authors: Elste, Günther; Jugaku, Jun Bibcode: 1957ApJ...125..742E Altcode: Formulae for the calculation of partition functions are presented in a form appropriate for numerical calculations. Detailed applications are given for neutral and ionized helium for a range of temperatures and densities appropriate to the B stars. Title: The Atmospheres of the B Stars. III. The Composition of Tau Scorpii. Authors: Aller, L. H.; Elste, G.; Jugaku, J. Bibcode: 1957ApJS....3....1A Altcode: New measurements of line intensities in the spectrum of r Scorp , based on coude' plates secured at the Mount Wilson and McDonald Ohservatories, are discussed with the aid of a model atmosphere and Pecker's theory for medium-strong lines. The computational procedures are described in detail, with a view to their application to other stellar atmospheres. he abundances derived differ from those and by Traving for three reasons: (1) the newer equivalent widths differ systematically from those found with the older McDonald spectrographs; (2) a slightly different model atmosphere is employed; and (3) a precise theory of line formation is utilized. Different ions of the same element yield different curves of growth, whereas lines formed in the same layers tend to have similar curves of growth. The agreement between theory and observation is improved with the aid of a differential correction to the model atmosphere, but all ions of all elements cannot be equally well represented by the same model atmosphere. The largest uncertainties appear to come from poor f-values. Helium, carbon, nitrogen, oxygen, and silicon are observed in two stages of ionization; other elements are observed in only one stage of ionization. Title: The composition of τ Scorpii. Authors: Aller, L. H.; Elste, G.; Jugaku, J. Bibcode: 1957AJ.....62R...2A Altcode: 1957AJ.....62....2A Measurements of line intensities in the spectrum of r Scorpii are discussed with th~ aid of a model atmosphere and Pecker's theory for lines of medium strength. The abundances derived differ from those found by Unsold and by Traving for three reasons: (i) the newer equivalent widths are systematically smaller, (2) a slightly different model atmosphere is employed, and (3) a precise theory of line formation is utilized. As has been noted previously for silicon, different ions of the same element have different curves of growth. This effect is strikingly exhibited in ~ Pegasi where silicon is observed in three stages of ionization. Differential corrections may be applied when the model does not quite represent the observations. The largest uncertainties arise from poor J-values. The abundance of helium is particularly difficult to establish because of uncertainties in the line-broadening theory and in the damping constants. The abundances of the heavier elements, expressed as log NeIern~t~Nhydr0g~, are as follows: Carbon' -4.3 Neon -3.14 Nitrogen -3.74 Magnesium - 3.7 Oxygen -3.37 Aluminum -5.6 Silicon -4.37 Helium, carbon, nitrogen, oxygen, and silicon are observed in two stages of ionization; other elements are observed in only one stage of ionization. The Observatory, University of i~Iichigan, Ann Arbor, AIThh. Title: Computation of individual curves of growth. Authors: Elste, G. Bibcode: 1957AJ.....62S..14E Altcode: It is shown that when theoretical equivalent widths of absorption lines are calculated precisely for a model atmosphere on the mechanism of pure absorption and following the theory of Pecker, the resulting curve of growth depends on the variation of the number of absorbing atoms with depth as well as on the Doppler width and on the wave length. Calculations performed for the solar spectrum are based on a model atmosphere derived from A. K. Pierce's photoelectric observations of the limb-darkening and energy distribution. Fifteen elements were selected for which f-values and equivalent widths are known with sufficient accuracy. For each element the lines were arranged in groups according to excitation potential and wave length. A pair of points defining a theoretical curve of growth in the transition region was then computed for each line group. The computations were carried out with the electronic computers, MIDAC and IBM 650 of the University of Michigan. Corresponding calculations for model atmospheres of B stars were carried out using graphical integration methods. The results show that the shape and position of the curve of growth depend strongly on the stage of ionization as well as on the excitation potential and wave length. University of Michigan, Ann Arbor, Mich. Title: Theoretical Line Intensities and the Spectrum of Tau Scorpii Authors: Elste, Günther; Jugaku, Jun; Aller, L. H. Bibcode: 1956PASP...68...23E Altcode: No abstract at ADS Title: Theoretical line intensities and spectrum of τ: Scorpii. Authors: Aller, L. H.; Elste, G.; Jugaku, J. Bibcode: 1956AJ.....61....1A Altcode: The model atmosphere for r Scorpii, recently calculated by G. Traving, is revised using the same temperature distribution but a surface gravity 2 X io4 dynes/cm2. The profile of H~, calculated with the absorption coefficients given by the new Kolb theory shows a satisfactory agreement with the observations. The equivalent widths of the Silil and Siiv lines, computed by the corrected Pecker theory and checked by precise numerical integrations, give the same silicon/ hydrogen ratio substantiating the adopted model. The Sjiii and Siiv lines follow different curves of growth, not merely because of the different damping constants but also because of the changing numbers of atoms with depth. The silicon/hydrogen ratio is smaller than that found by Traving and more nearly in accord with that found for the sun. Untversity of Alich?gan Observatory, Ann Arbor, Mich. Title: Die Mitte-Rand-Variation schwacher bis mittelstarker Fraunhoferlinien auf der Sonnenscheibe. Mit 16 Textabbildungen Authors: Elste, G. Bibcode: 1955ZA.....37..184E Altcode: No abstract at ADS Title: Die Entzerrung von Spektrallinien unter Verwendung von Voigtfunktionen Title: Die Entzerrung von Spektrallinien unter Verwendung von Voigtfunktionen Title: Equalization of spectral lines using Voigt functions; Authors: Elste, Günther H. Bibcode: 1954PhDT........15E Altcode: No abstract at ADS Title: The correction of spectral lines by using Voigt functions (Die Entzerrung von Spektrallinien unter Verwendung von Voigtfunktionen) Authors: Elste, Günther Bibcode: 1953VeGoe...6..194E Altcode: No abstract at ADS Title: Die Entzerrung von Spektrallinien unter Verwendung von Voigtfunktionen. Mit 8 Textabbildungen Authors: Elste, G. Bibcode: 1953ZA.....33...39E Altcode: No abstract at ADS