Sub-m s−1 upper limits from a deep HARPS-N radial-velocity search for planets orbiting HD 166620 and HD 144579

A Anna John*, A Collier Cameron*, J P Faria, A Mortier, T G Wilson, L Malavolta, L A Buchhave, X Dumusque, M López-Morales, R D Haywood, K Rice, A Sozzetti, D W Latham, S Udry, F Pepe, M Pinamonti, A Vanderburg, A Ghedina, R Cosentino, M StalportB A Nicholson, A Fiorenzano, E Poretti

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Minimizing the impact of stellar variability in radial velocity (RV) measurements is a critical challenge in achieving the 10 cm s−1 precision needed to hunt for Earth twins. Since 2012, a dedicated programme has been underway with HARPS-N, to conduct a blind RV rocky planets search (RPS) around bright stars in the Northern hemisphere. Here we describe the results of a comprehensive search for planetary systems in two RPS targets, HD 166620 and HD 144579. Using wavelength-domain line-profile decorrelation vectors to mitigate the stellar activity and performing a deep search for planetary reflex motions using a trans-dimensional nested sampler, we found no significant planetary signals in the data sets of either of the stars. We validated the results via data-splitting and injection recovery tests. Additionally, we obtained the 95th percentile detection limits on the HARPS-N RVs. We found that the likelihood of finding a low-mass planet increases noticeably across a wide period range when the inherent stellar variability is corrected for using scalpelsU-vectors. We are able to detect planet signals with Msin i ≤ 1 M⊕ for orbital periods shorter than 10 d. We demonstrate that with our decorrelation technique, we are able to detect signals as low as 54 cm s−1, which brings us closer to the calibration limit of 50 cm s−1 demonstrated by HARPS-N. Therefore, we show that we can push down towards the RV precision required to find Earth analogues using high-precision radial velocity data with novel data-analysis techniques.
Original languageEnglish
Pages (from-to)1687-1704
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date4 Aug 2023
Publication statusPublished - Oct 2023


  • Line: profiles
  • Techniques: radial velocities
  • Planets and satellites: detection
  • Stars: activity


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