scholarly journals Assisting Extrasolar Planetary Detection Through the Determination of Stellar Space Orientations

1985 ◽  
Vol 112 ◽  
pp. 97-100 ◽  
Author(s):  
Laurance R. Doyle
Keyword(s):  
Spectral Line ◽  
Intensity Distribution ◽  
Orbital Plane ◽  
Speckle Interferometry ◽  
Line Of Sight ◽  
Line Profiles ◽  
Stellar Rotation ◽  
Short Term ◽  
Rotation Periods

Various methods outlined for indirect planetary detection would greatly benefit (in some cases require) the determination of the planetary orbital plane, which is theoretically equivalent to the stellar equatorial plane. Determining the stellar space orientation, therefore, would greatly benefit extrasolar planetary detection.We utilize stellar rotation periods determined from short-term variations in Call H&K sunspot emission combined with both stellar radii measurements and Doppler broadened spectral line profiles to get the stellar inclination to the line of sight.The clocklike, on the plane-of-the-sky component determination utilizes the concentration of sunspot associated plage areas at central stellar latitudes when viewed in Call H or K emission. One can perform Call H&K emission speckle interferometry to measure the clocklike angle of this stellar Call H&K emission band, modeling it as an elliptical intensity distribution. Both components should be determinable to within ten degrees for at least resolvable fifth magnitude stars.

Determination of Particle Densities and Line Profiles in Plasmas by Resonance Interferometry: A Feasibility Study using Computer Simulated Refractivity Data

1995 ◽  
Vol 50 (10) ◽  
pp. 902-914 ◽  
Author(s):  
C. Haas ◽  
G. Pretzier ◽  
H. Jäger
Keyword(s):  
Spectral Line ◽  
Feasibility Study ◽  
Particle Density ◽  
Detection Limits ◽  
High Accuracy ◽  
Line Profiles ◽  
Actual Problem ◽  
Density Determination

AbstractThe principles of resonance interferometry are described with regard to two applications: High accuracy particle density determination within plasmas and interferometrical determination of spectral line profiles. The usability of this technique is investigated numerically, and physical limits are given for the regions in which resonance interferometry may be employed successfully. The discussion and the results are helt general for making it possible to decide whether or not to apply this method for an actual problem. An example (an object being longitudinally homogeneous with respect to the direction of light: end-on observation) shows how to use the presented results for calculating the detection limits of the method for a given object geometry.

scholarly journals Computed Spectral Line Variations for Oblique Nonradial Pulsators

1986 ◽  
Vol 90 ◽  
pp. 234-234
Author(s):  
Dietrich Baade ◽  
Werner W. Weiss
Keyword(s):  
Spectral Line ◽  
Observational Data ◽  
Rotation Axis ◽  
Signal To Noise Ratio ◽  
Line Of Sight ◽  
Pulsation Velocity ◽  
Line Profiles ◽  
Signal To Noise ◽  
Velocity Amplitude ◽  
Mode Order

AbstractSpectral line profiles are computed for nonradially pulsating CP2 stars. For a range which currently is thought to be typical for these stars, the influence of six parameters on the line profiles is considered: mode order ℓ and degree m, pulsation velocity amplitude, the angle between the rotation and pulsation axis, the angle between the rotation axis and the line-of-sight, and the phase angle of the rotation. In view of the expected low signal-to-noise ratio of observational data it is investigated to what extent easily measurable, simple quantities can still be useful in discriminating between different modes.

scholarly journals 6Li in metal-poor halo stars: real or spurious?

2009 ◽  
Vol 5 (S265) ◽  
pp. 23-26 ◽  
Author(s):  
M. Steffen ◽  
R. Cayrel ◽  
P. Bonifacio ◽  
H.-G. Ludwig ◽  
E. Caffau
Keyword(s):  
Spectral Line ◽  
Isotopic Ratio ◽  
Line Profiles ◽  
Halo Stars ◽  
Convective Motions ◽  
Symmetric Line ◽  
Line Asymmetry ◽  
Red Wing

AbstractThe presence of convective motions in the atmospheres of metal-poor halo stars leads to systematic asymmetries of the emergent spectral line profiles. Since such line asymmetries are very small, they can be safely ignored for standard spectroscopic abundance analysis. However, when it comes to the determination of the 6Li/7Li isotopic ratio, q(Li)=n(6Li)/n(7Li), the intrinsic asymmetry of the 7Li line must be taken into account, because its signature is essentially indistinguishable from the presence of a weak 6Li blend in the red wing of the 7Li line. In this contribution we quantity the error of the inferred 6Li/7Li isotopic ratio that arises if the convective line asymmetry is ignored in the fitting of the λ6707 Å lithium blend. Our conclusion is that 6Li/7Li ratios derived by Asplund et al. (2006), using symmetric line profiles, must be reduced by typically Δq(Li) ≈ 0.015. This diminishes the number of certain 6Li detections from 9 to 4 stars or less, casting some doubt on the existence of a 6Li plateau.

scholarly journals The origin and evolution of dense regions in the ISM, and their role in spectral features

2012 ◽  
Vol 8 (S292) ◽  
pp. 99-99
Author(s):  
Diego Falceta-Gonçalves
Keyword(s):  
Spectral Line ◽  
Numerical Simulations ◽  
Molecular Clouds ◽  
Spectral Features ◽  
Line Profiles ◽  
Origin And Evolution ◽  
Secular Evolution ◽  
Theoretical Assumptions ◽  
Order Of Magnitude

AbstractIn this work we discuss the turbulent evolution of molecular clouds and the formation of dense structures within. Typically, the clumps evolution occurs apart from the secular evolution of the turbulent mother cloud due to its high density and large inertia. Despite of current theoretical assumptions we show, by means of numerical simulations, that the clump lifetimes are greater than previously thought by more than an order of magnitude. The presence of dense and long-lived clumps modifies the spectral line profiles of clouds, which are strongly related to the determination of Larson's relations. We address the main modifications of these if a realistic distribution of dense structures is taken into account.

scholarly journals IAU Colloquium No. 8: Experimental Techniques for the Determination of Fundamental Spectroscopic Data

1971 ◽  
Vol 8 ◽  
pp. 48-60
Author(s):  
Bruce W. Shore
Keyword(s):  
Spectral Line ◽  
Energy Levels ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Fast Time ◽  
Line Profiles ◽  
Atomic Properties ◽  
University Of Edinburgh ◽  
Experimental Spectroscopy

The last ten years have brought significant changes to the venerable disciplines of astronomy and spectroscopy. Traditionally astronomers sought wavelength catalogues of identified spectra lines. Under this impetus spectroscopists laboured to provide very accurate wavelength measurements and estimates of emission line intensity. Physicists and astronomers alike are now recognizing interest not only in such properties of isolated atoms as energy levels (or spectral-line wavelengths) and oscillator strengths, but also those atomic properties which depend upon the surroundings of a radiating atom: spectral-line profiles, excitation rates, and level populations. In turn, new uses of lasers and interferometers, fast time resolution, and simple but significantly different absorption and emission samples are altering experimental spectroscopy almost beyond recognition. The present colloquium, chaired by A.H.Cook (University of Edinburgh) and held at Imperial College, London, on September 1-4 1970, aimed to identify the means by which astronomers can now obtain fundamental atomic data.

scholarly journals The influence of NLTE effects in Fe I lines on an inverted atmosphere

2020 ◽  
Vol 633 ◽  
pp. A157 ◽  
Author(s):  
H. N. Smitha ◽  
R. Holzreuter ◽  
M. van Noort ◽  
S. K. Solanki
Keyword(s):  
Local Thermodynamic Equilibrium ◽  
Solar Physics ◽  
Accurate Determination ◽  
Line Of Sight ◽  
Line Pair ◽  
Line Profiles ◽  
Magnetic Elements ◽  
Non Local ◽  
Magnetohydrodynamic Simulation

Context. Ultraviolet overionisation of iron atoms in the solar atmosphere leads to deviations in their level populations based on Saha-Boltzmann statistics. This causes their line profiles to form in non-local thermodynamic equilibrium (NLTE) conditions. When inverting such profiles to determine atmospheric parameters, the NLTE effects are often neglected and other quantities are tweaked to compensate for deviations from the LTE. Aims. We investigate how the routinely employed LTE inversion of iron lines formed in NLTE underestimates or overestimates atmospheric quantities, such as temperature (T), line-of-sight velocity (vLOS), magnetic field strength (B), and inclination (γ) while the earlier papers have focused mainly on T. Our findings has wide-ranging consequences since many results derived in solar physics are based on inversions of Fe I lines carried out in LTE. Methods. We synthesized the Stokes profiles of Fe I 6301.5 Å and 6302.5 Å lines in both LTE and NLTE using a snapshot of a 3D magnetohydrodynamic simulation. The profiles were then inverted in LTE. We considered the atmosphere inferred from the inversion of LTE profiles as the fiducial model and compared it to the atmosphere resulting from the inversion of NLTE profiles. The observed differences have been attributed to NLTE effects. Results. Neglecting the NLTE effects introduces errors in the inverted atmosphere. While the errors in T can go up to 13%, in vLOS and B, the errors can go as high as 50% or above. We find these errors to be present at all three inversion nodes. Importantly, they survive degradation from the spatial averaging of the profiles. Conclusions. We provide an overview of how neglecting NLTE effects influences the values of T, vLOS, B, and γ that are determined by inverting the Fe I 6300 Å line pair, as observed, for example, by Hinode/SOT/SP. Errors are found at the sites of granules, intergranular lanes, magnetic elements, and basically in every region susceptible to NLTE effects. For an accurate determination of the atmospheric quantities and their stratification, it is, therefore, important to take the NLTE effects into account.

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