Evidence for 9 planets in the HD 10180 system

TL;DR

This study re-analyzes the HD 10180 system's radial velocity data, providing evidence for up to nine exoplanets, including two newly detected signals, making it potentially the star with the most known planets.

Contribution

The paper introduces a Bayesian analysis framework to identify and confirm multiple exoplanets in the HD 10180 system, revising previous planetary counts and detecting two new planets.

Findings

Evidence for up to nine planets in HD 10180.

Verification of the seventh signal and detection of two new signals.

Refined orbital parameters and mass estimates for the known planets.

Abstract

We re-analyse the HARPS radial velocities of HD 10180 and calculate the probabilities of models with differing numbers of periodic signals in the data. We test the significance of the seven signals, corresponding to seven exoplanets orbiting the star, in the Bayesian framework and perform comparisons of models with up to nine periodicities. We use posterior samplings and Bayesian model probabilities in our analyses together with suitable prior probability densities and prior model probabilities to extract all the significant signals from the data and to receive reliable uncertainties for the orbital parameters of the six, possibly seven, known exoplanets in the system. According to our results, there is evidence for up to nine planets orbiting HD 10180, which would make this this star a record holder in having more planets in its orbits than there are in the Solar system. We revise the uncertainties of the previously reported six planets in the system, verify the existence of the seventh signal, and announce the detection of two additional statistically significant signals in the data. If of planetary origin, these two additional signals would correspond to planets with minimum masses of 5.1$^{+3.1}_{-3.2}$ and 1.9$^{+1.6}_{-1.8}$ M$_{\oplus}$ on orbits with 67.55$^{+0.68}_{-0.88}$ and 9.655$^{+0.022}_{-0.072}$ days periods (denoted using the 99% credibility intervals), respectively.