A ~5 M_earth Super-Earth Orbiting GJ 436?: The Power of Near-Grazing Transits

TL;DR

This paper reports the potential discovery of a ~5 Earth-mass super-Earth around GJ 436, identified through transit perturbations and radial velocity signals, highlighting the power of near-grazing transits to detect low-mass exoplanets.

Contribution

It presents the first evidence of a low-mass super-Earth around a main-sequence star using transit and radial velocity data, emphasizing the significance of near-grazing transits for detection.

Findings

Possible super-Earth with ~5 M_earth around GJ 436

Detection via perturbations on an inner Neptune-mass planet

Near-grazing transits increase sensitivity to small inclination changes

Abstract

Most of the presently identified exoplanets have masses similar to that of Jupiter and therefore are assumed to be gaseous objects. With the ever-increasing interest in discovering lower-mass planets, several of the so-called super-Earths (1 M_earth<M<10 M_earth), which are predicted to be rocky, have already been found. Here we report the possible discovery of a planet around the M-type star GJ 436 with a minimum mass of 4.7+/-0.6 M_earth and a true mass of ~5 M_earth, which would make it the least massive planet around a main-sequence star found to date. The planet is identified from its perturbations on an inner Neptune-mass transiting planet (GJ 436b), by pumping eccentricity and producing variations in the orbital inclination. Analysis of published radial velocity measurements indeed reveals a significant signal corresponding to an orbital period that is very close to the 2:1 mean motion resonance with the inner planet. The near-grazing nature of the transit makes it extremely sensitive to small changes in the inclination.