Small Telescope Exoplanet Transit Surveys: XO

  • Nicolas Crouzet
Living reference work entry

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The XO project aims at detecting transiting exoplanets around bright stars from the ground using small telescopes. The original configuration of XO (McCullough et al. 2005) has been changed and extended as described here. The instrumental setup consists of three identical units located at different sites, each composed of two lenses equipped with CCD cameras mounted on the same mount. We observed two strips of the sky covering an area of 520∘2 for twice nine months. We build lightcurves for ∼20,000 stars up to magnitude R ≈ 12.5 using a custom-made photometric data reduction pipeline. The photometric precision is around 1–2% for most stars, and the large quantity of data allows us to reach a millimagnitude precision when folding the lightcurves on timescales that are relevant to exoplanetary transits. We search for periodic signals and identify several hundreds of variable stars and a few tens of transiting planet candidates. Follow-up observations are underway to confirm or reject these candidates. We found two close-in gas giant planets so far, in line with the expected yield.


Exoplanets Transits Photometry Small instruments Time-series 



N.C. gratefully acknowledges Peter R. McCullough as the founder and principal investigator of the XO project. The XO project was supported by NASA grant NNX10AG30G. This research has made use of the Extrasolar Planets Encyclopaedia (, Simbad database (, software (Lang et al. 2010), and Stellar Photometry Software (Janes and Heasley 1993).


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Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.Instituto de Astrofísica de CanariasSan Cristóbal de La Laguna, Santa Cruz de TenerifeSpain

Section editors and affiliations

  • Norio Narita
    • 1
    • 2
    • 3
  1. 1.Graduate School of Science, Department of AstronomyUniversity of TokyoTokyoJapan
  2. 2.Exoplanet Detection Project OfficeNational Astronomical Observatory of JapanTokyoJapan
  3. 3.Exoplanet Detection Project OfficeAstrobiology CenterTokyoJapan

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