Dr John Taylor j.k.taylor@keele.ac.uk
Detection of the Atmosphere of the 1.6 M ? Exoplanet GJ 1132 b
Southworth, John; Mancini, Luigi; Madhusudhan, Nikku; Mollière, Paul; Ciceri, Simona; Henning, Thomas
Authors
Luigi Mancini
Nikku Madhusudhan
Paul Mollière
Simona Ciceri
Thomas Henning
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 4s 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.
Journal Article Type | Article |
---|---|
Acceptance Date | Feb 27, 2017 |
Online Publication Date | Mar 31, 2017 |
Publication Date | Mar 31, 2017 |
Publicly Available Date | Mar 29, 2024 |
Journal | The Astronomical Journal |
Print ISSN | 0004-6256 |
Publisher | American Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 153 |
Issue | 4 |
Article Number | 191 |
DOI | https://doi.org/10.3847/1538-3881/aa6477 |
Keywords | planetary systems; stars: fundamental parameters; stars: individual (GJ 1132) |
Publisher URL | http://iopscience.iop.org/article/10.3847/1538-3881/aa6477/meta;jsessionid=73C450C154F51013BF652EE71F2FE650.c1.iopscience.cld.iop.org |
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