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

A. Suárez Mascareño

TL;DR

This study tests the proposed giant planet Calpamos around the nearby star ζ^2 Ret using 28.8 years of archival radial velocities, joint activity indicators, and advanced statistical modeling. By fitting a global model that includes a stellar magnetic cycle, rotation via a Gaussian Process, and potential planetary signals, the authors demonstrate that the long-period RV variation arises from magnetic activity rather than a planet. They place stringent upper limits on additional companions across 1–4000 days, with habitable-zone planets constrained to $m_p\sin i$ of roughly 6–11 $M_⊕$ and overall mass limits below tens of Earth masses for most orientations; a true Jovian companion would require an almost strictly face-on geometry. The results effectively rule out Calpamos and similar planets in typical inclinations, refining our understanding of planet occurrence around ζ^2 Ret and informing the interpretation of technosignature-related hypotheses.

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 $ζ^2$ 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.

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

TL;DR

This study tests the proposed giant planet Calpamos around the nearby star ζ^2 Ret using 28.8 years of archival radial velocities, joint activity indicators, and advanced statistical modeling. By fitting a global model that includes a stellar magnetic cycle, rotation via a Gaussian Process, and potential planetary signals, the authors demonstrate that the long-period RV variation arises from magnetic activity rather than a planet. They place stringent upper limits on additional companions across 1–4000 days, with habitable-zone planets constrained to of roughly 6–11 and overall mass limits below tens of Earth masses for most orientations; a true Jovian companion would require an almost strictly face-on geometry. The results effectively rule out Calpamos and similar planets in typical inclinations, refining our understanding of planet occurrence around ζ^2 Ret and informing the interpretation of technosignature-related hypotheses.

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 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 sin , depending on orbital period. We show that the previously identified long-period RV signal is definitively caused by the magnetic cycle of the star.

Paper Structure

This paper contains 12 sections, 8 figures, 3 tables.

Table of Contents

  1. Introduction
  2. $\zeta^2$ Ret
  3. Potential presence of planets in the system
  4. Data
  5. Analysis
  6. Results and discussion
  7. Activity-only model
  8. Attempting to detect Calpamos
  9. Blind search of planets in the system
  10. Limits to the presence of planetary companions
  11. Conclusions
  12. Additional figures

Figures (8)

  • Figure 1: Artist impression of a spaceship arriving Calpamos with its three Earth-like moons in front of it. Taken from alien1979
  • Figure 2: Spectroscopic data used in this work.
  • Figure 3: Radial velocity data of $\zeta^2$ Ret with the best model fit (top) and the residuals after the fit (bottom), along with their respective Generalised Lomb Scargle periodograms Zechmeister2009.
  • Figure 4: Summary of the injection-recovery test performed to validate upper limits.
  • Figure 5: FIP periodogram of the full dataset. No significant power excess is found at any period.
  • ...and 3 more figures