J/A+A/507/417 Oxygen lines in solar granulation. I. (Pereira+, 2009)
Oxygen lines in solar granulation.
I. Testing 3D models against new observations with high spatial and spectral
resolution.
Pereira T.M.D., Kiselman D., Asplund, M.
<Astron. Astrophys. 507, 417 (2009)>
=2009A&A...507..417P 2009A&A...507..417P
ADC_Keywords: Sun ; Spectroscopy
Keywords: Sun: granulation - line: formation - Sun: photosphere
techniques: spectroscopic - techniques: high angular resolution
Abstract:
We seek to provide additional tests of the line formation of
theoretical 3D solar photosphere models. In particular, we set out to
test the spatially-resolved line formation at several viewing angles,
from the solar disk-centre to the limb and focusing on atomic oxygen
lines. The purpose of these tests is to provide additional information
on whether the 3D model is suitable to derive the solar oxygen
abundance. We also aim to empirically constrain the NLTE recipes for
neutral hydrogen collisions, using the spatially-resolved observations
of the OI 777nm lines.
Description:
We obtained solar observations of several lines at several positions
of the solar disk. Data were obtained in May 2007 with the TRIPPEL
spectrograph at the Swedish 1-m Solar Telescope (SST). The spectra
were obtained for three distinct wavelength windows at approx 615, 630
and 777nm. Each window covers ∼1nm. The spectra are spatially-resolved
in the solar surface, hence are given as 2D spectrograms. One axis
covers the wavelength and the other spatial position.
The observations are given for five positions in the solar disk,
ordered by mu, the cosine of the heliocentric angle. The objective was
to study the centre-to-limb variation of the lines. Active sun regions
were avoided. In total 150 spectrograms are given for each wavelength
window: 50 for the solar disk-centre (mu=1) and 25 for the other four
positions (mu=0.8, 0.6, 0.4, 0.2). The images were selected by
continuum contrast, hence their observed times are not the same for
the three windows.
The spectrograms are given as FITS files. Each file has two
Header/Data Units (HDU). The first HDU contains the reduced
spectrogram, a 2D array. The first dimension of the array contains
(FITS NAXIS1) corresponds to wavelength, and the second (FITS NAXIS2)
to spatial coordinate. The second HDU contains the continuum levels
obtained for each spatial point (1D array, length equal to the number
of spatial points in the spectrogram). To obtain the normalized
reduced spectrogram one has to divide each spectrum in the spectrogram
by the corresponding continuum level. The spectrograms have been
corrected for stray light and to minimize noise a Fourier filter has
been applied (details in the paper).
Important note: the wavelength scales have NOT been corrected for
solar rotation or gravitational redshift.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 99 450 Observations
wave/* . 15 Wavelength scale for the spectrograms,
lambda=6150, 6300 and 7770Å,
mu=0.2, 0.4, 0.6, 0.8 and 1
sp/* . 15 Directories by wavelength (spAAAAA) with
individual spectra in FITS format
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See also:
J/A+A/508/1403 : Oxygen lines in solar granulation. II. (Pereira+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 nm lambda Approximate central wavelength of filter
6- 20 F15.7 d JD Julian date
23- 28 F6.2 deg HLAT Heliographic latitude in the Stony-Hurst
coordinate system
31- 36 F6.2 deg HLON Heliographic longitude in the Stony-Hurst
coordinate system
39- 43 F5.3 --- mu Cosine of the heliocentric angle
46- 50 F5.3 --- e_mu Error in mu
53- 56 F4.2 --- S Amount of straylight removed from the
the spectra. Expressed as a percentage of
the pseudo-continuum intensity
59- 64 F6.4 arcsec/pix Conv Approximate conversion factor from the
spectrogram's spatial axis to angular
coordinate in arcsec
67- 86 A20 --- FITSfile Path and filename of each spectrogram,
in subdirectory "sp"
88- 99 A12 --- WaveFile Name of the file with wavelength scale,
in subdirectory "wave"
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Byte-by-byte Description of file: wave/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 nm Lambda Wavelength scale for the corresponding
spectrograms (1)
--------------------------------------------------------------------------------
Note (1): It decreases with pixel number (ie., first pixel of the
spectrogram's wavelength axis has the largest wavelength)
--------------------------------------------------------------------------------
Acknowledgements:
Tiago M. D. Pereira, tiago(at)mso.anu.edu.au
(End) Patricia Vannier [CDS] 24-Sep-2009