The profiles of fraunhofer lines in the presence of zeeman splitting

For the case of pure absorption lines (LTE) a method is described which enables the general computation of Zeeman-split line profiles. The magnetic field vector, the Doppler shift and the line absorption coefficient is permitted to vary arbitrarily with optical depth. Elliptical birefringence (e.g., Faraday rotation) of the solar atmosphere is taken into account. Some numerical examples are given and some interesting behaviors of the line profiles are discussed.     

A new method for the multitemperature analysis of solar X-ray line emission

Solar Physics - An application of nonlinear least squares methods for determining the temperature models of coronal active regions, based on the measured X-ray line intensities, is described. These...     

The fraunhofer lines classifications by asymmetry changes inside the profiles in the spectrum of the Sun

The method of asymmetry change inside Fraunhofer lines profiles is proposed. New digital spectra with high resolution were used. It was shown that asymmetry may change repeatedly by value and a sign inside the spectral line profile. The lines can be classified in three groups on asymmetry changes inside the profiles.     

The forbidden line [Ca ii] λ7323 in the fraunhofer spectrum

New observations of the [Caii] 7323 Fraunhofer line are reported. The blending H₂O line was weak at the time of observation. Accurate estimates of the centre-limb variation of the equivalent width of the [Caii] transition are obtained and shown to be consistent with the calcium abundance log N(Ca) = 6.33.     

A generalized method for deriving mass-loss rates: The first order moment of unsaturated P Cygni line profiles

For the case of optically thin lines, we show that the relation existing between the first order momentW ₁ (E()/E _c –1)(–₁₂)d of a P Cygni profile and the quantityMn(level), whereM is the mass-loss rate of the central star andn(level) the fractional abundance of the ion under study, is in fact independent of any Sobolev-type approximations used for the transfer of line radiation, contrary to what has been assumed in some previous works (Castoret al., 1981; Surdej, 1982). Consequently, all results established in the context of very rapidly expanding atmospheres and mainly referring to the non-dependence ofW ₁ vs various physical (underlying photospheric absorption line, limb darkening, etc.) and geometrical (velocity fieldv(r), etc.) effects remain unchanged for arbitrary (e.g non-Sobolev type) outward-accelerating velocity laws.Whenever applied with caution, Equation (50) thus provides a very powerful means of deriving mass-loss rates—with a total uncertainty less than 60 percent—from the measurementW ₁ of unsaturated P Cygni profiles observed in the spectrum of early—as well as late—type stars, quasars, etc.     

A simple technique for calculating line profiles of inhomogeneous planetary atmospheres

The computation of synthetic spectra for planetary atmospheres in which multiple scattering is important usually requires lengthy numerical work. We obtain solutions to the appropriate equation of radiative transfer by use of a variational principle whose extremum is essentially the reflectivity. When considering light diffusely reflected from the atmospheres of the outer planets, the technique reduces the computational work enormously and is applicable to models in which the albedo varies strongly with optical depth as well.     

Applications of Fourier analysis to broadening of stellar line profiles

Turbulence dominated by eddies of a finite size produces effects on a line profile which are similar to both macro- and micro-turbulence but which are at the same time neither. It is suggested that one of these effects in the Fourier transform domain, namely the narrowing of the first natural sidelobe relative to the width of the main lobe, can be used as an indicator of the dominance of finite-sized eddies (mesoturbulence). An examination of some existing solar data shows that finitesized eddy models fit the observed sidelobe widths better than do models computed with any reasonable combination of micro- and macro-turbulent broadenings (Paper III).     

On the asymmetry of selected fraunhofer lines,II

The asymmetry of 11 absorption lines of neutral iron was determined from observations made with the double-pass system on the horizontal solar telescope Asu-5. An attempt was made to interpret this asymmetry in terms of progressive sound waves. The value of asymmetry computed theoretically was shown to be on average only 20 % of the observed value.     

A new exact method for line radiative transfer

We present a new method, the coupled escape probability (CEP), for exact calculation of line emission from multi-level systems, solving only algebraic equations for the level populations. The CEP formulation of the classical two-level problem is a set of linear equations , and we uncover an exact analytic expression for the emission from two-level optically thick sources that holds as long as they are in the 'effectively thin' regime. In a comparative study of a number of standard problems, the CEP method outperformed the leading line transfer methods by substantial margins.
The algebraic equations employed by our new method are already incorporated in numerous codes based on the escape probability approximation. All that is required for an exact solution with these existing codes is to augment the expression for the escape probability with simple zone-coupling terms. As an application, we find that standard escape probability calculations generally produce the correct cooling emission by the C  ii 158-μm line but not by the ³P lines of O  i .     

Precise measurements of spectral line profiles

We present a method of precise measurements of spectral line profiles that was elaborated and tested on the Main Stellar Spectrograph (MSS) of the 6-m BTA telescope. The method allows discarding corrections for flat field. To take account of inhomogeneity of the CCD chip sensitivity, two spectra are recorded, shifted against each other along the dispersion by one column. Recurrent ratios between the photo responses of the CCD pixels let us determine their relative sensitivity and correct the line profiles. To eliminate various instability effects, the spectra are registered with the use of a cyclic shift procedure along the dispersion, and a synchronous electronic image transfer across the spectrum dispersion (along the CCD matrix columns).     

Absorption line profiles and rotational velocities for 59 stars

Absorption lines of Heii, Hei, Mgii, and other ions have been measured in coudé spectral tracings for 59 slowly and rapidly rotating sourthern O, B and A stars on the Main Sequence. All 668 separate line profiles have been analyzed with a procedure of differential corrections by least-squares to yield the following parameters and their error estimates: half-width, central depth, equivalent width, and shape parameter. The shape parameter includes Voigt profiles and also ‘super-Gaussian’ and ‘super-damping’ profiles. In addition, separately-measured line profiles in each star have been superimposed to yield better composite profiles with smaller errors. In addition, a preliminary value ofv sini is derived for each line by deconvolving it with both the intrinsic and instrumental profiles, and a mean value (including error bar) is derived for each star. The resulting mean values ofv sini are only about 2/3 as large as the earlier results presented by Buscombe (1969). The inadequacies of the traditional procedure are discussed, and plans for using calculated non-LTE intrinsic line profiles including line limb darkening and also effects of rotational distortion, will be outlined.     

Variations of the asymmetry of disk-integrated solar line profiles

Mean line bisector positions were found for the neutral iron line at 5250.2 using disk-integrated sunlight. After correction for the apparent time variation of the instrumental profile, it was found that the mean bisector position was constant during the period from May 1982 to February 1983.The correlation between the total magnetic flux as measured at Mount Wilson and the line asymmetry results of Livingston is not high. In particular, the magnetic flux dropped in 1982, suggesting a large line asymmetry that was not observed. However, the correlation between the 30-day average of the mean magnetic field and Livingston's results is quite high (-0.95), suggesting that the asymmetry of the disk-integrated line profile is related to the old plage regions rather than to the active regions.Now at the Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, U.S.A.     

Spectral line profiles and neutron cross sections: New results concerning the analysis of Voigt functions

The Voigt functions, so important in spectroscopy and neutron physics, are represented as generalized hypergeometric functions (G-functions) of two real variables. A system of partial differential equations for the Voigt functions is derived. By applying Hölder's inequality to an integral representation of the Voigt functions apparently not known in the literature until now, lower and upper bounds are obtained. Moreover, from this representation an asymptotic expansion of Voigt functions for large values of one variable is extracted.     

A systematic analysis of the XMM-Newton background: IV

We show the results obtained in the FP7 European program EXTraS and in the ESA R&D ATHENA activity AREMBES aimed at a deeper understanding of the XMM-Newton background to better design the ATHENA mission. Thanks to an analysis of the full EPIC archive coupled to the information obtained by the Radiation Monitor we show the cosmic ray origin of the unfocused particle background and its anti-correlation with the solar activity. We show the first results of the effort to obtain informations about the particle component of the soft proton focused background.     

Calculation of line profiles of inhomogeneous solar formations

A generalized equation was obtained for calculation of line profiles of solar formations in the assumption of their inhomogeneity. Line profiles of homogeneous formations are a particular consequence of this equation. Analysis of the equation and line profiles calculated from it was carried out.     

On the depth dependence of the solar rotation velocity determined from fraunhofer lines

From 63 mostly unblended Fraunhofer lines measured along the solar east-west diameter the rotation velocity has been determined. The mean value is 1986 km s^#X2212;1. The velocity decreases with the optical depth in the photosphere. Over a range of 700 km the difference of the velocities is 41 m s^#X2212;1 for the Holweger-Müller atmosphere or 34 m s^#X2212;1 for the Harvard Smithsonian reference atmosphere.     

A multiple spot model for simultaneous solution of light curves and distorted line profiles of spotted stars

This paper is devoted to the effects of dark starspots on observed light curves and line profiles. A new formulation of the starspot model with multiple spots and arbitrary spot shapes is derived which allows for a numerical solution of light and colour curves and distorted line profiles simultaneously. The effects of differential rotation and the existence of a penumbra have also been considered. A parameter study demonstrates the influences of different spot parameters on the theoretical light curves and rotation profiles. The computer code is applicable for single stars as well as for eclipsing close binaries allowing for ellipticity effect and reflection effect.     

A high-resolution Fabry-Pérot spectrometer for emission line studies in planetary nebulae and other extended astronomical objects

We describe here a scanning piezo-electric Fabry-Pérot spectrometer operating in the photoncounting mode whose plate spacing and parallelism are maintained by a servo-controlled system, ensuring high accuracy, for the study of emission lines from extended astronomical objects in the spectral range 4500–7000 Å. Details of the optical set-up and the Data Acquisition System (DAS) are described. Its performance at the Cassegrain focus of the 1 m telescope at Kavalur is discussed. Some line profiles on planetary nebulae studied with the above spectrometer are also presented.     

Calculation of 5250.216 Å line profiles in sunspots

The assumptions of pure absorption and local thermodynamic equilibrium are sometimes used to calculate approximate spectral line profiles in cases where a rigorous treatment is impractical or impossible. In certain conditions, the profile is not completely defined under these assumptions.This work was done under NASA contract No. NAS8-26376 for the Space Sciences Laboratory, George C. Marshall Space Flight Center, Huntsville, Ala.