In space there will be no need to scream -- Limits to the presence of giant planets in the $\zeta^2$ Ret system

Abstract

The search for life beyond our Solar system has been a long and difficult endeavour. The majority of current efforts are focused on the potential detection of biosignatures. However, their detection and interpretation are extremely challenging. Technosignatures appear as an attractive alternative, given their expected univocal interpretation. In recent years, the number of publications discussing them have skyrocketted, both in their more rigurous and speculative sides. In this article, we explore the 28.8 years of archival radial velocity data of $\zeta^2$ Ret with the aim of detecting the proposed giant planet Calpamos, suspected source of a signal of technological origin. We performed a global model fitting the radial velocity data along with activity indicators and modelled the stellar magnetic cycle and rotation. The analysis rules out the presence of the proposed planet, as well as of any other planets more massive than 2-20 $\mathrm{M}_\oplus$ $m_{p}$ sin $i$, depending on orbital period. We show that the previously identified long-period RV signal is definitively caused by the magnetic cycle of the star.