J/A+A/423/1109 Center-to-limb variation of quiet Sun (Allende+, 2004)
Center-to-limb variation of solar line profiles as a test of
NLTE line formation calculations.
Allende Prieto C., Asplund M., Fabiani Bendicho P.
<Astron. Astrophys., 423, 1109-1117 (2004)>
=2004A&A...423.1109A 2004A&A...423.1109A (SIMBAD/NED BibCode)
ADC_Keywords: Sun ; Spectroscopy
Keywords: Sun: photosphere - line: formation - line: profiles
Abstract:
We present new observations of the center-to-limb variation of
spectral lines in the quiet Sun. Our long-slit spectra are corrected
for scattered light, which amounts to 4-8% of the continuum intensity,
by comparison with a Fourier transform spectrum of the disk center.
Different spectral lines exhibit different behaviors, depending on
their sensitivity to the physical conditions in the photosphere and
the range of depths they probe as a function of the observing angle,
providing a rich database to test models of the solar photosphere and
line formation.
Description:
Solar observations of the center-to-limb variation of several spectral
lines were carried out in October 22-23, 1997, with the Gregory Coude
Telescope (GCT) and its Czerny-Turner echelle spectrograph at the
Observatorio del Teide (Tenerife, Spain).
We secured spectra for 8 spectral setups in 6 different positions
across the solar disk, as summarized in Table 1.
Positions #1 to #5 were always at heliocentric angles theta = 0, 15,
30, 45, and 60 degrees (mu = cos(theta) = 1.00, 0.97, 0.87, 0.71, and
0.50) along a straight line crossing the center of the solar disk.
Position #6 was also selected along the same direction, sometimes at
theta = 75 degrees and others at 80 degrees (mu = 0.26 or 0.17).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 105 8 Observations
sp/* . 48 Individual spectra
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm Lambda Central wavelength
6- 11 I6 --- R' Resolving power measured relative to that of
the Fourier transform spectrograph (FTS)
spectra
13- 17 F5.3 --- S Amount of scattered light expressed as a
fraction of the pseudo-continuum intensity.
19- 20 I2 deg thetamax Maximum value of the observing heliocentric
angle, theta
23- 35 A13 --- FTS00 theta=00° FTS spectrum file name, in sp/
37- 49 A13 --- FTS15 theta=15° FTS spectrum file name, in sp/
51- 63 A13 --- FTS30 theta=30° FTS spectrum file name, in sp/
65- 77 A13 --- FTS45 theta=45° FTS spectrum file name, in sp/
79- 91 A13 --- FTS60 theta=60° FTS spectrum file name, in sp/
93-105 A13 --- FTSmax theta=thetamax, 75 or 80°, FTS spectra
file name, in sp/
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 9 F9.4 0.1nm Lambda Wavelength
11- 20 F10.8 --- Flux Relative flux
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Acknowledgements: Carlos Allende Prieto, callende(at)astro.as.utexas.edu
(End) Patricia Vannier [CDS] 08-Mar-2005