On the eccentricity of Proxima b

TL;DR

This paper investigates the orbital eccentricity of Proxima b using Monte Carlo methods, revealing a trimodal distribution with three potential eccentricity values, and emphasizes the need for further observations to determine the true orbit.

Contribution

It introduces a novel analysis of eccentricity distribution for Proxima b, uncovering a trimodal density and highlighting the complexity of orbital parameter estimation.

Findings

Eccentricity distribution is trimodal with peaks at 0.25, 0.75, and 0.95.

Most likely eccentricity is 0.25.

Future observations are needed to identify the true eccentricity.

Abstract

We apply Monte Carlo projection to the radial velocity data set that Anglada Escude et al. (2016) use for the discovery of Proxima b. They find an upper limit to the orbital eccentricity of 0.35. To investigate the eccentricity issue further, we calculate a suite of monovariate and bivariate densities o eccentricity. After discarding apparent artifacts at eccentricity = 0 and = 1, we find that eccentricity has a trimodal sampling distribution: three chimeras or types of orbit compatible with the RV data set. The three modes or peaks in the density of eccentricity are located at eccentricity = 0.25, 0.75, and 0.95, with relative weights 0.79, 0.10, and 0.11. Future RV observations will clarify which of the three chimeras represents the true eccentricity of Proxima b. The most-likely estimate is eccentricity = 0.25, and our lower limit is eccentricity = 0.025. Our strategic, long-term goal is to elevate the orbital analyses of exoplanets to meet the challenges of sometimes complex probability density distributions.