Reducing activity-induced variations in a radial-velocity time series of the Sun as a star

A. F. Lanza, A. Collier Cameron, R. D. Haywood

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


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.
Original languageEnglish
Pages (from-to)3459–3464
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date13 Apr 2019
Publication statusPublished - Jul 2019


  • Techniques: radial velocities
  • Sun: activity
  • Planets and satellites: detection


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