TY - JOUR
T1 - Three Years of HARPS-N High-Resolution Spectroscopy and Precise Radial Velocity Data for the Sun
AU - Dumusque, X.
AU - Cretignier, M.
AU - Sosnowska, D.
AU - Buchschacher, N.
AU - Lovis, C.
AU - Phillips, D. F.
AU - Pepe, F.
AU - Alesina, F.
AU - Buchhave, L. A.
AU - Burnier, J.
AU - Cecconi, M.
AU - Cegla, H. M.
AU - Cloutier, R.
AU - Cameron, A. Collier
AU - Cosentino, R.
AU - Ghedina, A.
AU - Gonzalez, M.
AU - Haywood, R. D.
AU - Latham, D. W.
AU - Lodi, M.
AU - Lopez-Morales, M.
AU - Maldonado, J.
AU - Malavolta, L.
AU - Micela, G.
AU - Molinari, E.
AU - Mortier, A.
AU - Ventura, H. Perez
AU - Pinamonti, M.
AU - Poretti, E.
AU - Rice, K.
AU - Riverol, L.
AU - Riverol, C.
AU - Juan, J. San
AU - Segransan, D.
AU - Sozzetti, A.
AU - Thompson, S. J.
AU - Udry, S.
AU - Wilson, T. G
PY - 2021
Y1 - 2021
N2 - Context. The solar telescope connected to HARPS-N has been
observing the Sun since the summer of 2015. Such a high-cadence,
long-baseline data set is crucial for understanding spurious
radial-velocity signals induced by our Sun and by the instrument. On the
instrumental side, this data set allowed us to detect sub- m s−1 systematics that needed to be corrected for.
Aims. The goals of this manuscript are to (i) present a new
data reduction software for HARPS-N, (ii) demonstrate the improvement
brought by this new software during the first three years of the HARPS-N
solar data set, and (iii) release all the obtained solar products, from
extracted spectra to precise radial velocities.
Methods. To correct for the instrumental systematics observed
in the data reduced with the current version of the HARPS-N data
reduction software (DRS version 3.7), we adapted the newly available
ESPRESSO DRS (version 2.2.3) to HARPS-N and developed new optimised
recipes for the spectrograph. We then compared the first three years of
HARPS-N solar data reduced with the current and new DRS.
Results. The most significant improvement brought by the new
DRS is a strong decrease in the day-to-day radial-velocity scatter, from
1.27 to 1.07 m s−1; this is thanks to a more robust method
to derive wavelength solutions, but also to the use of calibrations
closer in time. The newly derived solar radial-velocities are also
better correlated with the chromospheric activity level of the Sun in
the long term, with a Pearson correlation coefficient of 0.93 compared
to 0.77 before, which is expected from our understanding of stellar
signals. Finally, we also discuss how HARPS-N spectral ghosts
contaminate the measurement of the calcium activity index, and we
present an efficient technique to derive an index free of instrumental
systematics.
Conclusions. This paper presents a new data reduction software
for HARPS-N and demonstrates its improvements, mainly in terms of
radial-velocity precision, when applied to the first three years of the
HARPS-N solar data set. Those newly reduced solar data, representing an
unprecedented time series of 34 550 high-resolution spectra and precise
radial velocities, are released alongside this paper. Those data are
crucial to understand stellar activity signals in solar-type stars
further and develop the mitigating techniques that will allow us to
detect other Earths.
AB - Context. The solar telescope connected to HARPS-N has been
observing the Sun since the summer of 2015. Such a high-cadence,
long-baseline data set is crucial for understanding spurious
radial-velocity signals induced by our Sun and by the instrument. On the
instrumental side, this data set allowed us to detect sub- m s−1 systematics that needed to be corrected for.
Aims. The goals of this manuscript are to (i) present a new
data reduction software for HARPS-N, (ii) demonstrate the improvement
brought by this new software during the first three years of the HARPS-N
solar data set, and (iii) release all the obtained solar products, from
extracted spectra to precise radial velocities.
Methods. To correct for the instrumental systematics observed
in the data reduced with the current version of the HARPS-N data
reduction software (DRS version 3.7), we adapted the newly available
ESPRESSO DRS (version 2.2.3) to HARPS-N and developed new optimised
recipes for the spectrograph. We then compared the first three years of
HARPS-N solar data reduced with the current and new DRS.
Results. The most significant improvement brought by the new
DRS is a strong decrease in the day-to-day radial-velocity scatter, from
1.27 to 1.07 m s−1; this is thanks to a more robust method
to derive wavelength solutions, but also to the use of calibrations
closer in time. The newly derived solar radial-velocities are also
better correlated with the chromospheric activity level of the Sun in
the long term, with a Pearson correlation coefficient of 0.93 compared
to 0.77 before, which is expected from our understanding of stellar
signals. Finally, we also discuss how HARPS-N spectral ghosts
contaminate the measurement of the calcium activity index, and we
present an efficient technique to derive an index free of instrumental
systematics.
Conclusions. This paper presents a new data reduction software
for HARPS-N and demonstrates its improvements, mainly in terms of
radial-velocity precision, when applied to the first three years of the
HARPS-N solar data set. Those newly reduced solar data, representing an
unprecedented time series of 34 550 high-resolution spectra and precise
radial velocities, are released alongside this paper. Those data are
crucial to understand stellar activity signals in solar-type stars
further and develop the mitigating techniques that will allow us to
detect other Earths.
KW - Sun: activity
KW - Techniques: radial velocities
KW - Methods: data analysis
KW - Instrumentation: spectrographs
KW - Astronomical databases: miscellaneous
KW - Planets and satellites: detection
U2 - 10.1051/0004-6361/202039350
DO - 10.1051/0004-6361/202039350
M3 - Journal article
SN - 0004-6361
VL - 648
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A103
ER -