Precise radius estimates for the exoplanets WASP-1b and WASP-2b

David Charbonneau, Joshua N. Winn, Mark E. Everett, David W. Latham, Matthew J. Holman, Gilbert A. Esquerdo, Francis T. O'Donovan

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


We present precise z-band photometric time series spanning times of transit of the two exoplanets recently discovered by the SuperWASP collaboration. We find planetary radii of 1.44 ± 0.08 and 1.04 ± 0.06 RJ for WASP-1b and WASP-2b, respectively. These error estimates include both random errors in the photometry and also the uncertainty in the stellar masses. Our results are 5 times more precise than the values derived from the discovery data alone. Our measurement of the radius of WASP-2b agrees with previously published models of hot Jupiters that include both a 20 M⊖ core of solid material and the effects of stellar insolation. In contrast, we find that the models cannot account for the large size of WASP-1b, even if the planet has no core. Thus, we add WASP-1b to the growing list of hot Jupiters that are larger than expected. This suggests that "inflated" hot Jupiters are more common than previously thought and that any purported explanations involving highly unusual circumstances are disfavored.

Original languageEnglish (US)
Pages (from-to)1322-1327
Number of pages6
JournalAstrophysical Journal
Issue number2 I
StatePublished - Apr 1 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Planetary systems
  • Stars: individual (WASP-1, WASP-2)
  • Techniques: photometric


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