J/A+A/648/A103 Thorium line list (Dumusque+, 2021)
Three years of HARPS-N high-resolution spectroscopy and precise radial velocity
data for the Sun.
Dumusque X., Cretignier M., Sosnowska D., Buchschacher N., Lovis C.,
Phillips D.F., Pepe F., Alesina F., Buchhave L.A., Burnier J., Cecconi M.,
Cegla H.M., Cloutier R., Collier Cameron A., Cosentino R., Ghedina A.,
Gonzalez M., Haywood R.D., Latham D.W., Lodi M., Lopez-Morales M.,
Maldonado J., Malavolta L., Micela G., Molinari E., Mortier A.,
Perez Ventura H., Pinamonti M., Poretti E., Rice K., Riverol L.,
Riverol C., San Juan J., Segransan D., Sozzetti A., Thompson S.J., Udry S.,
Wilson T.G.
<Astron. Astrophys. 648, A103 (2021)>
=2021A&A...648A.103D 2021A&A...648A.103D (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: Sun: activity - techniques: radial velocities -
methods: data analysis - instrumentation: spectrographs -
astronomical databases: miscellaneous -
planets and satellites: detection
Abstract:
The solar telescope connected to HARPS-N has observed the Sun since
the summer of 2015. Such high-cadence, longbaseline data set is
crucial for understanding spurious radial-velocity signals induced by
our Sun and by the instrument. Aims. This manuscript describes the
data reduction performed to obtain unprecedented radial-velocity
precision for the three years of solar data released along with this
paper.
The nearly continuous observation of our Sun has allowed us to detect
sub-m/s systematics in the HARPS-N solar data reduced by the current
data reduction software. To improve the radial-velocity precision of
the solar data, we reduced them using the new ESPRESSO data reduction
software and developed new recipes to mitigate the detected
systematics.
The most significant improvement brought by the new data reduction is
a strong decrease in the day-to-day radial-velocity scatter, from 1.28
to 1.09m/s; this is thanks to a more stable method to derive
wavelength solutions, but also to the use of calibrations closer in
time. We also demonstrate that the current HARPS-N data reduction
software induces a long-term drift of 1.2m/s, due to the use of
non-stable thorium lines. As a result, the old solar RVs are weakly
correlated to the solar magnetic cycle, which is not expected. On the
contrary, the newly derived radial velocities are much more
correlated, with a Pearson correlation coefficient of 0.93. We also
discuss a special correction for ghost contamination, to extract a
calcium activity index free from instrumental systematics.
Our work leads toward a better understanding of the instrumental and
data reduction systematics affecting the HARPSN spectrograph. The new
solar data released, representing an unprecedented time-series of
34550 high-resolution spectra and precise radial velocities will be
crucial to understanding stellar activity signals of solar-type stars,
with the goal of enabling the detection of other Earths.
Description:
Thorium line list used to compute drift map wavelength solutions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
th_line.dat 35 2041 Thorium line list used by the new HARPS-N DRS
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See also:
J/A+A/468/1115 : Thorium and argon lines in the visible (Lovis+, 2007)
J/ApJS/211/4 : Thorium spectrum from 250nm to 5500nm (Redman+, 2014)
Byte-by-byte Description of file: th_line.dat
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Bytes Format Units Label Explanations
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1- 10 F10.5 0.1nm lambda Line wavelength in vacuum (1)
12- 18 F7.5 0.1nm e_lambda Line wavelength error in vacuum (1)
20- 22 A3 --- El Element at the origin of the line
24- 25 I2 --- HARPS-Norder Spectral order in HARPN
27- 35 F9.4 --- HARPS-Npixel Pixel position on HARPN detector
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Note (1): From Redman et al. 2014ApJS..211....4R 2014ApJS..211....4R, Cat. J/ApJS/211/4.
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Acknowledgements:
Xavier Dumusque, Xavier.Dumusque(at)unige.ch
Astronomy Department Geneva University, Switzerland
(End) X. Dumusque [Geneva Univ., Switzerland], P. Vannier [CDS] 18-Feb-2021