scholarly journals Quantifying Resolving Power in Astronomical Spectra

2013 ◽  
Vol 30 ◽  
Author(s):  
J. Gordon Robertson
Keyword(s):  
Spectral Line ◽  
Spatial Dimension ◽  
Spectral Lines ◽  
Resolving Power ◽  
Noise Power ◽  
Line Spread Function ◽  
Fabry Perot ◽  
Lorentzian Profile ◽  
Multi Mode ◽  
Line Spread

AbstractThe spectral resolving power R = λ/δλ is a key property of any spectrograph, but its definition is vague because the ‘smallest resolvable wavelength difference’ δλ does not have a consistent definition. Often, the FWHM is used, but this is not consistent when comparing the resolution of instruments with different forms of spectral line-spread function. Here, two methods for calculating resolving power on a consistent scale are given. The first method is based on the principle that two spectral lines are just resolved when the mutual disturbance in fitting the fluxes of the lines reaches a threshold (here equal to that of sinc2 profiles at the Rayleigh criterion). The second criterion assumes that two spectrographs have equal resolving powers if the wavelength error in fitting a narrow spectral line is the same in each case (given equal signal flux and noise power). The two criteria give similar results and give rise to scaling factors that can be applied to bring resolving power calculated using the FWHM on to a consistent scale. The differences among commonly encountered line-spread functions are substantial, with a Lorentzian profile (as produced by an imaging Fabry–Perot interferometer) being a factor of two worse than the boxy profile from a projected circle (as produced by integration across the spatial dimension of a multi-mode fibre) when both have the same FWHM. The projected circle has a larger FWHM than its true resolution, so using FWHM to characterise the resolution of a spectrograph which is fed by multi-mode fibres significantly underestimates its true resolving power if it has small aberrations and a well-sampled profile.

The Use of Fabry-Perot Filters for Spectral Scanning

1969 ◽  
Vol 1 (6) ◽  
pp. 293-294
Author(s):  
M. D. Waterworth
Keyword(s):  
Stellar Atmospheres ◽  
Spectral Lines ◽  
Resolving Power ◽  
Doppler Broadening ◽  
Collisional Broadening ◽  
Fabry Perot

In designing a stellar spectrograph, it is pointless to exceed the resolving power necessary to obtain all the information from the spectrum of a star. This is limited mainly by atomic thermal motions, giving rise to the Doppler broadening of spectral lines, by turbulence and rotation of the stellar atmospheres in which the lines are formed, and by collisional broadening.

scholarly journals SDSS-IV MaNGA: Modeling the Spectral Line-spread Function to Subpercent Accuracy

2021 ◽  
Vol 161 (2) ◽  
pp. 52
Author(s):  
David R. Law ◽  
Kyle B. Westfall ◽  
Matthew A. Bershady ◽  
Michele Cappellari ◽  
Renbin Yan ◽  
...  
Keyword(s):  
Spectral Line ◽  
Line Spread Function ◽  
Spread Function ◽  
Line Spread

scholarly journals The Value of Fabry-Perot Interferometry in Studying Long-Term Convective Line Shifts

1999 ◽  
Vol 170 ◽  
pp. 278-285
Author(s):  
Robert S. McMillan ◽  
T. H. Bressi ◽  
J. L. Montani ◽  
T. L. Moore ◽  
M. L. Perry ◽  
...  
Keyword(s):  
Broad Spectrum ◽  
Signal To Noise Ratio ◽  
Absorption Lines ◽  
Resolving Power ◽  
Photon Flux ◽  
High Signal ◽  
Dwarf Stars ◽  
Line Spread Function ◽  
Fabry Perot ◽  
Solar Type

AbstractSmall < 10 m s−1 variations of radial velocity (RV) with multi-year periods in solar-type stars may be indistinguishable from the effects induced on lines by stellar activity cycles (Dravins 1985; Saar & Donahue 1997). Dravins (1992) recommended a resolving power R > 3 × 105 to measure accurately the subtle changes in the shapes of bisectors of photospheric absorption lines driven by changes of granular convection in slowly rotating dwarf stars. Butler et al. (1996) measure impressively small amplitudes of RVs by using echelle spectrographs that cover a broad spectrum. However, to cover a broad spectrum the resolving power is typically limited to < 7 × 104, and the necessary presence of the iodine absorption spectrum may make it difficult to measure convective line shifts contemporaneously with the RV time series. Furthermore, to reach an RV accuracy of ± 3 ms−1 the whole profile of each line is used, thus maximizing the possibility that changes in the shapes of the lines’ C-bisectors could induce an apparent variation of RV.Dravins (1985) recommended the exclusive use of the steep flanks of photospheric absorption lines to minimize the effects of convection on apparent RV. McMillan et al. (1993, 1994) demonstrated that such RV measurements made with a Fabry-Perot etalon (FPE) interferometer in transmission can be stable in the presence of stellar line variations seen by other investigators whose measurements were not based exclusively on line flanks. Dravins also prescribed high resolving power, high signal-to-noise ratio, high instrumental contrast, and low instrumental wings to analyze the rest of the line profile for convectively-driven changes (Dravins 1978, 1987, 1992). A double- or multiple-pass FPE scanning whole line profiles can provide high R, high contrast, low wings, and a stable, symmetrical line spread function with small (portable) optics, although the low photon efficiency will restrict its use to a few carefully selected stars. The spectral classes of these stars should span the spectral classes of the stars being monitored by others for planets. We describe a possible implementation of this concept that has the potential for adequate photon flux: observing symbiotically through another instrument on a 6-m to 10-m class telescope.

scholarly journals Astro-comb: revolutionizing precision spectroscopy in astrophysics

2008 ◽  
Vol 4 (S253) ◽  
pp. 499-501
Author(s):  
Claire E. Cramer ◽  
Chih-Hao Li ◽  
Andrew J. Benedick ◽  
Alexander G. Glenday ◽  
Franz X. Kärtner ◽  
...  
Keyword(s):  
Doppler Shift ◽  
Extrasolar Planets ◽  
Frequency Comb ◽  
Laser Frequency ◽  
Spectral Lines ◽  
Resolving Power ◽  
Long Term Stability ◽  
Fabry Perot ◽  
Line Spacing ◽  
Wide Line

AbstractSearches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision better than 60cm/s. To find a 1-Earth mass planet in an Earth-like orbit, a precision of 5cm/s is necessary. The combination of a laser frequency comb with a Fabry-Perot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration. Here we report the fabrication of such a filtered laser comb with up to 40 GHz (~1 Angstrom) line spacing, generated from a 1 GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb (astro-comb) is well matched to the resolving power of high-resolution astrophysical spectrographs. The astrocomb should allow a precision as high as 1cm/s in astronomical readial velocity measurements.

scholarly journals From the Vector to Scalar Perturbations Addition in the Stark Broadening Theory of Spectral Lines

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 176
Author(s):  
Valery Astapenko ◽  
Andrei Letunov ◽  
Valery Lisitsa
Keyword(s):  
Spectral Line ◽  
Stark Effect ◽  
Coulomb Field ◽  
Spectral Lines ◽  
Alternative Methods ◽  
Scalar Perturbation ◽  
Numerical Comparison ◽  
Line Shapes ◽  
Stark Effects ◽  
The Impact

The effect of plasma Coulomb microfied dynamics on spectral line shapes is under consideration. The analytical solution of the problem is unachievable with famous Chandrasekhar–Von-Neumann results up to the present time. The alternative methods are connected with modeling of a real ion Coulomb field dynamics by approximate models. One of the most accurate theories of ions dynamics effect on line shapes in plasmas is the Frequency Fluctuation Model (FFM) tested by the comparison with plasma microfield numerical simulations. The goal of the present paper is to make a detailed comparison of the FFM results with analytical ones for the linear and quadratic Stark effects in different limiting cases. The main problem is connected with perturbation additions laws known to be vector for small particle velocities (static line shapes) and scalar for large velocities (the impact limit). The general solutions for line shapes known in the frame of scalar perturbation additions are used to test the FFM procedure. The difference between “scalar” and “vector” models is demonstrated both for linear and quadratic Stark effects. It is shown that correct transition from static to impact limits for linear Stark-effect needs in account of the dependence of electric field jumping frequency in FFM on the field strengths. However, the constant jumping frequency is quite satisfactory for description of the quadratic Stark-effect. The detailed numerical comparison for spectral line shapes in the frame of both scalar and vector perturbation additions with and without jumping frequency field dependence for the linear and quadratic Stark effects is presented.

Understanding the concept of resolving power in the Fabry–Perot interferometer using a digital simulation

2006 ◽  
Vol 27 (5) ◽  
pp. 1111-1119 ◽  
Author(s):  
I Juvells ◽  
A Carnicer ◽  
J Ferré-Borrull ◽  
E Martín-Badosa ◽  
M Montes-Usategui
Keyword(s):  
Digital Simulation ◽  
Resolving Power ◽  
Fabry Perot

Multi-mode all Fiber Interferometer based on Fabry-Perot Multi-cavity and its Temperature Response

Optik ◽  
2017 ◽  
Vol 147 ◽  
pp. 232-239 ◽  
Author(s):  
Y. Lopez-Dieguez ◽  
J.M. Estudillo-Ayala ◽  
D. Jauregui-Vazquez ◽  
J.M. Sierra-Hernandez ◽  
L.A. Herrera-Piad ◽  
...  
Keyword(s):  
Temperature Response ◽  
Fabry Perot ◽  
Multi Mode

scholarly journals Determination of metallicity of the HR7914 solar-like star

2003 ◽  
pp. 69-74 ◽  
Author(s):  
Oliver Vince ◽  
Istvan Vince
Keyword(s):  
Spectral Line ◽  
Stellar Atmosphere ◽  
Astronomical Observatory ◽  
Program Package ◽  
Spectral Lines ◽  
Iron Abundance ◽  
Microturbulent Velocity

By using the Blackwell program package by R.O. Gray, the metallicity of the HR7914 solar-like star was determined. The program package utilizes measured equivalent widths of several chosen neutral iron spectral lines from the observed spectra, appropriate atomic and spectral line parameters and adequate Kurucz?s stellar atmosphere models. The method is based on determination of the minimum dispersion of the iron abundance versus microturbulent velocity functions for the selected neutral iron spectral lines. The spectra were observed at National Astronomical Observatory Rozhen (NAO Rozhen), Bulgaria, using the 2m-telescope and Coude spectrograph. They were reduced with the IRAF program package. The measurement of the spectral line parameters was done with the SPE program package. The metallicity of the HR7914 solar-like star was determined to be 0.02.

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