Colour-magnitude diagrams of transiting Exoplanets - I. Systems with parallaxes

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


Broad-band flux measurements centred around [3.6 μm] and [4.5 μm] obtained with Spitzer during the occultation of seven extrasolar planets by their host stars have been combined with parallax measurements to compute the absolute magnitudes of these planets. Those measurements are arranged in two colour–magnitude diagrams. Because most of the targets have sizes and temperatures similar to brown dwarfs, they can be compared to one another. In principle, this should permit inferences about exoatmospheres based on knowledge acquired by decades of observations of field brown dwarfs and ultracool stars’ atmospheres. Such diagrams can assemble all measurements gathered so far and will provide help in the preparation of new observational programmes. In most cases, planets and brown dwarfs follow similar sequences. HD 2094589b and GJ 436b are found to be outliers, so is the night side of HD 189733b. The photometric variability associated with the orbital phase of HD 189733b is particularly revealing. The planet exhibits what appears like a spectral type and chemical transition between its day and night sides: HD 189733b straddles the L–T spectral class transition, which would imply different cloud coverage on each hemisphere. Methane absorption could be absent at its hotspot but present over the rest of the planet.
Original languageEnglish
Pages (from-to)L61-L64
Number of pages4
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date7 Jan 2014
Publication statusPublished - 21 Mar 2014


  • planets and satellites
  • binaries: eclipsing
  • brown dwarfs
  • stars:distances
  • Hertzsprung–Russell and colour–magnitude diagrams
  • planetary systems


Dive into the research topics of 'Colour-magnitude diagrams of transiting Exoplanets - I. Systems with parallaxes'. Together they form a unique fingerprint.

Cite this