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Colour-magnitude diagrams of transiting Exoplanets - II. A larger sample from photometric distances

Triaud, Amaury H.M.J.; Lanotte, Audrey A.; Smalley, Barry; Gillon, Michaël

Colour-magnitude diagrams of transiting Exoplanets - II. A larger sample from photometric distances Thumbnail


Amaury H.M.J. Triaud

Audrey A. Lanotte

Michaël Gillon


Colour–magnitude diagrams form a traditional way of presenting luminous objects in the Universe and compare them to each other. Here, we estimate the photometric distance of 44 transiting exoplanetary systems. Parallaxes for seven systems confirm our methodology. Combining those measurements with fluxes obtained while planets were occulted by their host stars, we compose colour–magnitude diagrams in the near and mid-infrared. When possible, planets are plotted alongside very low mass stars and field brown dwarfs, who often share similar sizes and equilibrium temperatures. They offer a natural, empirical, comparison sample. We also include directly imaged exoplanets and the expected loci of pure blackbodies. Irradiated planets do not match blackbodies; their emission spectra are not featureless. For a given luminosity, hot Jupiters’ daysides show a larger variety in colour than brown dwarfs do and display an increasing diversity in colour with decreasing intrinsic luminosity. The presence of an extra absorbent within the 4.5 µm band would reconcile outlying hot Jupiters with ultra-cool dwarfs’ atmospheres. Measuring the emission of gas giants cooler than 1000 K would disentangle whether planets’ atmospheres behave more similarly to brown dwarfs’ atmospheres than to blackbodies, whether they are akin to the young directly imaged planets, or if irradiated gas giants form their own sequence.

Journal Article Type Article
Acceptance Date Jul 11, 2014
Online Publication Date Aug 20, 2014
Publication Date Oct 11, 2014
Publicly Available Date May 26, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 444
Issue 1
Pages 711 -728
Keywords planets and satellites: atmospheres, binaries: eclipsing, brown dwarfs, stars: distances, Hertzsprung–Russell and colour–magnitude diagrams, planetary systems
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