Taylor, JK, Mancini, L, Madhusudhan, N, Molliere, P, Ciceri, S and Henning, T (2017) Detection of the Atmosphere of the 1.6 M ⊕ Exoplanet GJ 1132 b. The Astronomical Journal, 153 (4).

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Abstract

Detecting the atmospheres of low-mass, low-temperature exoplanets is a high-priority goal on the path to ultimately detecting biosignatures in the atmospheres of habitable exoplanets. High-precision HST observations of several super-Earths with equilibrium temperatures below 1000 K have to date all resulted in featureless transmission spectra, which have been suggested to be due to high-altitude clouds. We report the detection of an atmospheric feature in the atmosphere of a 1.6 ${M}_{\oplus }$ transiting exoplanet, GJ 1132 b, with an equilibrium temperature of ~600 K and orbiting a nearby M dwarf. We present observations of nine transits of the planet obtained simultaneously in the griz and JHK passbands. We find an average radius of 1.43 ± 0.16 ${R}_{\oplus }$ for the planet, averaged over all the passbands, and a radius of 0.255 ± 0.023 ${R}_{\odot }$ for the star, both of which are significantly greater than previously found. The planet radius can be decomposed into a "surface radius" at ~1.375 ${R}_{\oplus }$ overlaid by atmospheric features that increase the observed radius in the z and K bands. The z-band radius is 4σ higher than the continuum, suggesting a strong detection of an atmosphere. We deploy a suite of tests to verify the reliability of the transmission spectrum, which are greatly helped by the existence of repeat observations. The large z-band transit depth indicates strong opacity from H2O and/or CH4 or a hitherto-unconsidered opacity. A surface radius of 1.375 ± 0.16 ${R}_{\oplus }$ allows for a wide range of interior compositions ranging from a nearly Earth-like rocky interior, with ~70% silicate and ~30% Fe, to a substantially H2O-rich water world.

Item Type: Article
Additional Information: © 2017. The American Astronomical Society. All rights reserved.
Uncontrolled Keywords: planetary systems; stars: fundamental parameters; stars: individual (GJ 1132)
Subjects: Q Science > QB Astronomy
Q Science > QB Astronomy > QB799 Stars
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Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Depositing User: Symplectic
Date Deposited: 07 Apr 2017 08:43
Last Modified: 26 Mar 2019 15:53
URI: http://eprints.keele.ac.uk/id/eprint/3201

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