scholarly journals Solar Oscillator Strengths as a Diagnostic Tool

1990 ◽  
Vol 138 ◽  
pp. 35-40
Author(s):  
E. A. Gurtovenko ◽  
R. I. Kostik ◽  
R. J. Rutten
Keyword(s):  
Spectral Line ◽  
Diagnostic Tool ◽  
Chemical Elements ◽  
Laboratory Data ◽  
Solar Spectrum ◽  
Oscillator Strengths ◽  
Small Subset ◽  
Solar Photosphere ◽  
Line Formation ◽  
Line Depth

We briefly review the Kiev program for determining oscillator strengths of Fraunhofer lines from the optical solar spectrum, which has recently resulted in a compilation of solar gf-values for 1958 lines from 40 chemical elements (Gurtovenko and Kostik 1989). These gf-values were determined empirically by fitting solar lines using standard plane-parallel LTE modelling. Errors in this modelling propagate into the gf-values; reversely, the deviations in the latter may serve as diagnostics of the modelling and thus of spectral line formation in the solar photosphere. For a small subset, comparison with reliable laboratory data can be made; for other lines there is information in the differences between fits of the line area and of the line depth.

scholarly journals Formation Depths of Spectral Lines in Cepheids

1995 ◽  
Vol 155 ◽  
pp. 373-374
Author(s):  
Michael D. Albrow ◽  
P. L. Cottrell
Keyword(s):  
Spectral Line ◽  
Velocity Fields ◽  
Radial Velocities ◽  
Spectral Lines ◽  
Line Formation ◽  
Ionisation Potential ◽  
Velocity Gradients ◽  
Different Levels ◽  
Line Depth

There has been a number of observational programmes that have endeavoured to investigate the atmospheric velocity fields in Cepheids (e.g., Sanford 1956, Wallerstein et al. 1992, Butler 1993). These studies measured the radial velocities of lines of different strength, excitation and ionisation potential as these provide an indication of line formation at different levels in the atmosphere. From these measurements, the presence of velocity gradients can be inferred, but determination of the magnitude of such gradients requires knowledge of the spectral line depth of formation. Through dynamical modelling we are endeavouring to ascertain what is actually being measured in the above observational programmes.

The chemical composition of the sun1This review is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (4) ◽  
pp. 327-331 ◽  
Author(s):  
N. Grevesse ◽  
M. Asplund ◽  
A.J. Sauval ◽  
P. Scott
Keyword(s):  
Chemical Elements ◽  
Molecular Data ◽  
Solar Neighborhood ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Solar Photosphere ◽  
International Colloquium ◽  
Laboratory Plasmas ◽  
Selection Of

We have very recently re-determined the abundances of nearly all the available chemical elements in the solar photosphere, from lithium to thorium (Asplund et al. Annu. Rev. Astron. Astrophys. 47, 481 (2009)). This new complete and homogeneous analysis results from a very careful selection of spectral lines of all the indicators of the abundances present in the solar photospheric spectrum, from a discussion of the atomic and molecular data, and from an analysis of these lines based on a new 3D model of the solar outer layers, taking non-LTE effects into account when possible. We present these new results, compare them with other recent solar data as well as with recent results for the solar neighborhood, and discuss some of their most important implications as well as some of the atomic data we still urgently need.

scholarly journals Observations on spatial variations of the Sr I 4607 Å scattering polarization signals at different limb distances with ZIMPOL

2019 ◽  
Vol 630 ◽  
pp. A67 ◽  
Author(s):  
Sajal Kumar Dhara ◽  
Emilia Capozzi ◽  
Daniel Gisler ◽  
Michele Bianda ◽  
Renzo Ramelli ◽  
...  
Keyword(s):  
Spectral Line ◽  
Spatial Scales ◽  
Solar Spectrum ◽  
Spatial Variations ◽  
Stokes Parameters ◽  
Small Scale ◽  
Solar Photosphere ◽  
Local Anisotropy ◽  
Polarization Signal ◽  
The Continuum

Context. The Sr I 4607 Å spectral line shows one of the strongest scattering polarization signals in the visible solar spectrum. The amplitude of this polarization signal is expected to vary at granular spatial scales, due to the combined action of the Hanle effect and the local anisotropy of the radiation field. Observing these variations would be of great interest because it would provide precious information on the small-scale activity of the solar photosphere. At present, few detections of such spatial variations have been reported. This is due to the difficulty of these measurements, which require combining high spatial (∼0.1″), spectral (≤20 mÅ), and temporal resolution (< 1 min) with increased polarimetric sensitivity (∼10−4). Aims. We aim to detect spatial variations at granular scales of the scattering polarization peak of the Sr I 4607 Å line at different limb distances, and to study the correlation with the continuum intensity. Methods. Using the Zurich IMaging POLarimeter (ZIMPOL) system mounted at the GREGOR telescope and spectrograph in Tenerife, Spain, we carried out spectro-polarimetric measurements to obtain the four Stokes parameters in the Sr I line at different limb distances, from μ = 0.2 to μ = 0.8, on the solar disk. Results. Spatial variations of the scattering polarization signal in the Sr I 4607 Å line, with a spatial resolution of about 0.66″, are clearly observed at every μ. The spatial scale of these variations is comparable to the granular size. A statistical analysis reveals that the linear scattering polarization amplitude in this Sr I spectral line is positively correlated with the intensity in the continuum, corresponding to the granules, at every μ.

scholarly journals Effects of Acoustic Waves on Spectral Line Profiles

1980 ◽  
Vol 51 ◽  
pp. 211-211
Author(s):  
Lawrence E. Cram
Keyword(s):  
Velocity Field ◽  
Spectral Line ◽  
Acoustic Waves ◽  
Line Shift ◽  
Solar Photosphere ◽  
Line Formation ◽  
Thermal Velocity ◽  
State Variables ◽  
Velocity Amplitude ◽  
Short Period

AbstractAlmost all studies of spectral line formation in the presence of non-thermal velocity fields have been made assuming that the only effect of the velocity field is to produce a Doppler shift of the absorption and emission coefficients. However, a non-thermal velocity field will entail velocity-correlated fluctuations in temperature, pressure, level populations, and other parameters of the line formation problem. Using a time-dependent dynamical calculation describing the propagation of non-linear, radiatively-damped short period (P = 30s) acoustic waves in the solar photosphere, Cram, Keil and Ulmschneider (1980) have shown that velocity-correlated fluctuations in state variables (particularly the temperature) may lead to important effects in line broadening, line shifts and asymmetries, and in line-shift oscillations. Upwardly propagating waves generally produce significant redshifts in the cores of medium-strong Fe I lines, and the increased ratio of observed line shift to wave velocity amplitude would significantly modify the results of kinematic studies of high frequency line shifts such as those of Deubner (1976) and Keil (1980).Cram (1980) has further explored dynamical effects in the formation of Fe I and Fe II lines by using the “microturbulence” limit, wherein an average is made over the phase of the wave before the transfer equation is solved. Except for weak, high EP Fe II lines, the predicted solar lines are redshifted and show a “red” asymmetry. For a model of Arcturus the lines are often shifted to the blue, but it does not appear that this model can account for the observed differences between solar and Arcturan line asymmetries (Gray 1980).

scholarly journals Neutral oxygen spectral line formation revisited with new collisional data: large departures from LTE at low metallicity

2009 ◽  
Vol 500 (3) ◽  
pp. 1221-1238 ◽  
Author(s):  
D. Fabbian ◽  
M. Asplund ◽  
P. S. Barklem ◽  
M. Carlsson ◽  
D. Kiselman
Keyword(s):  
Spectral Line ◽  
Line Formation ◽  
Spectral Line Formation ◽  
Low Metallicity

scholarly journals VI. Corrections to the computed lengths of waves of light published in the Philosophical Transactions of the year 1868

1872 ◽  
Vol 162 ◽  
pp. 89-109
Keyword(s):  
Spectral Line ◽  
Royal Society ◽  
Wave Length ◽  
Solar Spectrum ◽  
Spectral Lines ◽  
Fifth Order ◽  
Principal Lines ◽  
General Table

In a paper communicated to the Royal Society in the year 1867, and printed in the Philosophical Transactions for 1868, I attempted the computation of the Lengths of Waves of Light for all the lines which Kirchhoff had observed in the Solar Spectrum, by adopting an algebraical formula of the fifth order, and substituting in it for every spectral line the value of Kirchhoff’s measure for that line, the numerical bases of the formula being derived from Fraunhofer’s and Ditscheiner’s measures of the wave-lengths for six principal lines. Subsequently I obtained the means of comparing many of my computed results with measures of wave-lengths by Ångstrȍm and Ditscheiner, and l found that the discordances were far larger than I had anticipated. I remarked, however, “By means of the comparison........ there is no difficulty in computing for any other line the correction that ought to be applied to the wave-length in the principal Tables, in order to exhibit the true wave-lengths on Ditscheiner’s scale, without appreciable error.” Want of leisure long prevented me from entering upon the examination necessary for preparing, in a form easy for applications, the correction which my numbers required. Lately, however, I have taken it up; and I have constructed a Table of corrections to the numbers of my Table generally, and I have applied them, both to the general Table of wave-lengths and to the values of wave-lengths for the spectral lines of the atmosphere and several metals (the accurate exhibition of which was, in fact, the first object of my computations). I now offer these corrections and corrected numbers for the acceptance of the Royal Society.

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