HST PanCET programme: a flat optical transmission spectrum for the Hot Jupiter WASP-101b

Alexander D. Rathcke*, Lars A. Buchhave, João M. Mendonça, David K. Sing, Mercedes López-Morales, Munazza K. Alam, Gregory W. Henry, Nikolay K. Nikolov, A. García Muñoz, Thomas Mikal-Evans, Hannah R. Wakeford, Leonardo A. Dos Santos, Vinesh Maguire Rajpaul

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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We present an optical transmission spectrum of the hot Jupiter WASP-101b. We observed three primary transits with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph, covering a wavelength range from 0.3 to 1 μm. The observations suffer from significant systematics that we model using Gaussian Processes. Kernel selection for the Gaussian Processes is performed in a data-driven approach through Bayesian model comparison. We find a flat and featureless transmission spectrum, corroborating a previous measurement obtained with HST/Wide-Field Camera 3 in the 1–1.7 μm range. The spectrum is consistent with high-altitude clouds located at less than 100 μbar. This cloud layer completely blocks our view into deeper parts of the atmosphere and makes WASP-101b the cloudiest gas giant observed so far. We compute a series of temperature-pressure profiles for WASP-101b and compare these to condensation curves for cloud particles, which match clouds composed of silicates. We also include 13 transits observed with Transiting Exoplanet Survey Satellite and use these to refine system parameters.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Pages (from-to)582-594
Publication statusPublished - 2023

Bibliographical note

Please note correction: https://doi.org/10.1093/mnras/stad1411

In the originally published version of this manuscript, the Acknowledgements section inadvertently omitted acknowledging a collaborator for their significant contribution to this work.

This error has been corrected.


  • Methods: data analysis
  • Methods: observational
  • Planets
  • Planets and satellites: atmospheres
  • Satellites: gaseous planets


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