Analysis of the public HARPS/ESO spectroscopic archive -- Jupiter-like planets around HD 103891 and HD 105779

TL;DR

This study analyzes a 15-year HARPS/ESO spectroscopic archive to discover long-period Jupiter-like exoplanets, identifying two new candidates and emphasizing the value of long-term radial velocity surveys for understanding planetary systems.

Contribution

The paper presents the discovery of two Jupiter analogs around FGK stars using an automated detection algorithm and long-term RV data, highlighting the potential for Gaia astrometry to determine their exact masses.

Findings

Identified two Jupiter-like planets with periods around 5-6 years.

Derived orbital parameters using nested sampling techniques.

Planets have minimum masses of approximately 0.6 to 1.4 Jupiter masses.

Abstract

Aims. We use the recently published database (Trifonov et al. 2020) of radial velocities (RVs) that were derived from fifteen years of HARPS/ESO observations to search for planet candidates. Methods. For targets with sufficient RV data, we apply an automated algorithm to identify significant periodic signals and fit a Keplerian model for orbital estimates. We also search the auxiliary data of stellar-activity indices and compare our findings with existing literature, to detect periodic RV signals that have no counterpart in the activity timeseries. The most convincing signals are then manually inspected to designate additional false planet detection, focusing the search on long-period (P > 1 000 d) massive candidates around FGK dwarf stars. Results. We identify two Jupiter analogs, in orbit around the slightly evolved F8V star HD 103891 and the Solar-like star HD 105779. We use nested sampling to derive their orbital parameters, and find their orbital periods to be 1919 +/- 16 d and 2412 +/- 54 d, while their minimum masses are 1.44 +/- 0.02 M Jup and 0.64 +/- 0.06 M Jup , respectively. While the orbit of HD 103891 b is slightly eccentric (e = 0.31 +/- 0.03), that of HD 105779 b is likely circular (e < 0.16). Conclusions. With minimum astrometric signatures of 59 and 42 $\mu$as, HD 103891 b and HD 105779 b join the growing sample of planets whose exact masses may soon be derived with Gaia astrometry. This finding also highlights the importance of long-term RV surveys to study planetary occurrence beyond the snow line of Solar-like stars.