The RoPES project with HARPS and HARPS-N. I. A system of super-Earths orbiting the moderately active K-dwarf HD 176986

TL;DR

This paper reports the discovery of two super-Earth exoplanets orbiting the K-dwarf star HD 176986 using combined radial velocity data from HARPS and HARPS-N, and discusses stellar activity analysis.

Contribution

It introduces a new planetary system discovery around HD 176986 and demonstrates the effectiveness of combined RV analysis techniques on active stars.

Findings

Two super-Earths with masses of 5.74 and 9.18 Earth masses discovered

Planets orbit at 0.063 and 0.119 AU with periods of 6.49 and 16.82 days

Star's activity pattern analyzed to improve RV techniques

Abstract

We report the discovery of a system of two super-Earths orbiting the moderately active K-dwarf HD 176986. This work is part of the RoPES RV program of G- and K-type stars, which combines radial velocities (RVs) from the HARPS and HARPS-N spectrographs to search for short-period terrestrial planets. HD 176986 b and c are super-Earth planets with masses of 5.74 and 9.18 M$_{\oplus}$, orbital periods of 6.49 and 16.82 days, and distances of 0.063 and 0.119 AU in orbits that are consistent with circular. The host star is a K2.5 dwarf, and despite its modest level of chromospheric activity (log(R'hk) = - 4.90 +- 0.04), it shows a complex activity pattern. Along with the discovery of the planets, we study the magnetic cycle and rotation of the star. HD 176986 proves to be suitable for testing the available RV analysis technique and further our understanding of stellar activity.