Homogeneous planet masses

I. Reanalysis of archival HARPS radial velocities

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
² Mullard Space Science Laboratory, University College London, Dorking RH5 6NT, UK
³ University Observatory Munich, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 Munich, Germany
⁴ Sub-department of Astrophysics, Department of Physics, University of Oxford, Oxford OX1 3RH, UK
⁵ Department of Physics, University of Warwick, Coventry CV4 7AL, UK

^★ Corresponding author; hannah.osborne.19@ucl.ac.uk

Received: 5 September 2024
Accepted: 6 November 2024

Abstract

Empirical exoplanet mass–radius relations have been used to study the demographics and compositions of small exoplanets for many years. However, the heterogeneous nature of these measurements hinders robust statistical analysis of this population, particularly with regard to the masses of planets. For this reason, we perform a homogeneous and consistent re-analysis of the radial velocity (RV) observations of 87 small exoplanets using publicly available HARPS RV data and the fitting toolkit Pyaneti. For the entire sample, we ran 12 different models to investigate the impact of modelling choices, including the use of multidimensional Gaussian processes (GPs) to mitigate stellar activity. We find that the way orbital eccentricity is modelled can significantly impact the RV amplitude found in some cases. We also find that the addition of a GP to mitigate stellar activity impacts the RV amplitude found; though the results are more robust if the GP is modelled on activity indicators in addition to the RVs. The RV amplitude found for every planet in our sample using all the models is made available for other groups to perform demographics studies. Finally, we provide a list of recommendations for the RV community moving forward.