Observational Consequences of the Recently Proposed Super-Earth Orbiting GJ436

TL;DR

This study critically examines the proposed super-Earth orbiting GJ436, testing its observational consistency and finding no strong evidence for its existence despite the plausibility of the hypothesis.

Contribution

The paper evaluates the observational data against the proposed two-planet model, providing a comprehensive analysis that challenges previous claims of detection.

Findings

The proposed model conflicts with radial velocity and eclipse timing data.

Alternative two-planet models are plausible but not uniquely supported.

Current data do not definitively confirm the existence of the super-Earth.

Abstract

Ribas and collaborators have recently proposed that an additional, ~5 M_earth planet orbits the transiting planet host star GJ436. Long-term dynamical interactions between the two planets leading to eccentricity excitation might provide an explanation for the transiting planet's unexpectedly large orbital eccentricity. In this paper we examine whether the existence of such a second planet is supported by the available observational data when the short-term interactions that would result from its presence are accounted for. We find that the model for the system suggested by Ribas and collaborators lead to predictions that are strongly inconsistent with the measured host star radial velocities, transiting planet primary and secondary eclipse times, and transiting planet orbital inclinations. A search for an alternative two planet model that is consistent with the data yields a number of plausible solutions, although no single one stands out as particularly unique by giving a significantly better fit to the data than the nominal single planet model. We conclude from this study that Ribas and collaborator's general hypothesis of an additional short-period planet in the GJ436 system is still plausible, but that there is not sufficient evidence to support their claim of a planet detection.