J/A+A/669/A39 HARPS and HARPS-N solar radial velocities (Al Moulla+, 2023)
Stellar signal components seen in HARPS and HARPS-N solar radial velocities.
Al Moulla K., Dumusque X., Figueira P., Lo Curto G., Santos N.C., Wildi F.
<Astron. Astrophys. 669, A39 (2023)>
=2023A&A...669A..39A 2023A&A...669A..39A (SIMBAD/NED BibCode)
ADC_Keywords: Sun ; Radial velocities ; Optical
Keywords: stars: activity - stars: individual: Sun -
techniques: radial velocities
Abstract:
Radial velocity (RV) measurements induced by the presence of planets
around late-type stars are contaminated by stellar signals that are of
the order of a few meters per second in amplitude, even for the
quietest stars. Those signals are induced by acoustic oscillations,
convective granulation patterns, active regions co-rotating with the
stellar surface, and magnetic activity cycles.
This study investigates the properties of all coherent stellar signals
seen on the Sun on timescales up to its sidereal rotational period. By
combining HARPS and HARPS-N solar data spanning several years, we are
able to clearly resolve signals on timescales from minutes to several
months.
We use a Markov Chain Monte Carlo (MCMC) mixture model to determine
the quality of the solar data based on the expected airmass- magnitude
extinction law. We then fit the velocity power spectrum of the cleaned
and heliocentric RVs with all known variability sources, to recreate
the RV contribution of each component.
After rejecting variations caused by poor weather conditions, we are
able to improve the average intra- day root mean square (RMS) value by
a factor of ∼1.8. On sub-rotational timescales, we are able to fully
recreate the observed RMS of the RV variations. In order to also
include rotational components and their strong alias peaks introduced
by nightly sampling gaps, the alias powers are accounted for by being
redistributed to the central frequencies of the rotational harmonics.
Conclusions. In order to enable a better understanding and mitigation
of stellar activity sources, their respective impact on the total RV
must be well-measured and characterized. We are able to recreate RV
components up to rotational timescales, which can be further used to
analyse the impact of each individual source of stellar signals on the
detectability of exoplanets orbiting very quiet solar-type stars and
test the observational strategies of RV surveys.
Description:
The table contains the HARPS detrended solar radial velocities (RVs).
The HARPS-N solar RVs have already been released and can be downloaded
from the Data & Analysis Centre for Exoplanets (DACE) at
https://dace.unige.ch.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sunharps.dat 47 102027 HARPS detrended solar radial velocities
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Byte-by-byte Description of file: sunharps.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d BJD [58370.13/58929.05] Barycentric Julian Date
14- 26 E13.6 km/s RV [-0.01/0.01] Radial velocity
28- 34 F7.5 km/s e_RV [0.0/0.01] Radial velocity uncertainty
36- 47 F12.10 --- q_RV [0.9/1.0] Quality flag
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Acknowledgements:
Khaled Al Moulla, khaled.almoulla[at]unige.ch
(End) Patricia Vannier [CDS] 10-Nov-2022