Reducing activity-induced variations in a radial-velocity time series of the Sun as a star
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The radial velocity of the Sun as a star is affected by its surface convection and magnetic activity. The moments of the cross-correlation function between the solar spectrum and a binary line mask contain information about the stellar radial velocity and line-profile distortions caused by stellar activity. As additional indicators, we consider the disc-averaged magnetic flux and the filling factor of the magnetic regions. Here we show that the activity-induced radial-velocity fluctuations are reduced when we apply a kernel regression to these activity indicators. The disc-averaged magnetic flux proves to be the best activity proxy over a timescale of one month and gives a standard deviation of the regression residuals of 1.04 m/s, more than a factor of 2.8 smaller than the standard deviation of the original radial velocity fluctuations. This result has been achieved thanks to the high-cadence and time continuity of the observations that simultaneously sample both the radial velocity and the activity proxies.
Lanza , A F , Collier Cameron , A & Haywood , R D 2019 , ' Reducing activity-induced variations in a radial-velocity time series of the Sun as a star ' , Monthly Notices of the Royal Astronomical Society , vol. 486 , no. 3 , pp. 3459–3464 . https://doi.org/10.1093/mnras/stz1055
Monthly Notices of the Royal Astronomical Society
Copyright © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1093/mnras/stz1055
DescriptionAFL acknowledges support by INAF/Frontiera through the "Progetti Premiali" funding scheme of the Italian Ministry of Education, University, and Research. ACC acknowledges support from the Science & Technology Facilities Council (STFC) consolidated grant number ST/R000824/1. This work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute (R.D.H.).
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