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

Authors: Ignasi Ribas (ICE/CSIC-IEEC, Spain), Andreu Font-Ribera (ICE/CSIC-IEEC, Spain), Jean-Philippe Beaulieu (IAP, France)

(Submitted on 21 Jan 2008)

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 (i.e., with masses in the interval 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 4.8+/-0.6 M_earth and a true mass of ~5 M_earth, which makes it the least massive planet around a main-sequence star found to date. In contrast with other discoveries, the planet is identified from its perturbations on an inner Neptune-mass transiting planet (GJ 436b), by pumping eccentricity and producing secular 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. Such method holds great potential to push the detection limits of present and planned space missions to lower mass planets than those responsible for the transit.

Comments: 4 pages, 3 figures, submitted to The Astrophysical Journal Letters

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0801.3230v1 [astro-ph]

Submission history

From: Ignasi Ribas [view email]

[v1] Mon, 21 Jan 2008 17:06:16 GMT (98kb)

http://arxiv.org/abs/0801.3230