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

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.

5 pages, 3 figures, accepted for publication in The Astrophysical Journal Letters

References in corpus (3)

• Habitable planets around the star Gl 581?
• Detailed Models of super-Earths: How well can we infer bulk properties?
• The transiting exoplanet host star GJ 436: a test of stellar evolution models in the lower main sequence, and revised planetary parameters

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• What to Expect from Transiting Multiplanet Systems
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