Tests of the planetary hypothesis for PTFO 8-8695b

Liang Yu, Joshua N. Winn, Michaël Gillon, Simon Albrecht, Saul Rappaport, Allyson Bieryla, Fei Dai, Laetitia Delrez, Lynne Hillenbrand, Matthew J. Holman, Andrew W. Howard, Chelsea X. Huang, Howard Isaacson, Emmanuel Jehin, Monika Lendl, Benjamin T. Montet, Philip Muirhead, Roberto Sanchis-Ojeda, Amaury H.M.J. Triaud

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32 Scopus citations


The T Tauri star PTFO 8-8695 exhibits periodic fading events that have been interpreted as the transits of a giant planet on a precessing orbit. Here we present three tests of the planet hypothesis. First, we sought evidence for the secular changes in light-curve morphology that are predicted to be a consequence of orbital precession. We observed 28 fading events spread over several years and did not see the expected changes. Instead, we found that the fading events are not strictly periodic. Second, we attempted to detect the planet's radiation, based on infrared observations spanning the predicted times of occultations. We ruled out a signal of the expected amplitude. Third, we attempted to detect the Rossiter-McLaughlin effect by performing high-resolution spectroscopy throughout a fading event. No effect was seen at the expected level, ruling out most (but not all) possible orientations for the hypothetical planetary orbit. Our spectroscopy also revealed strong, time-variable, high-velocity Hα and Ca H & K emission features. All these observations cast doubt on the planetary hypothesis, and suggest instead that the fading events represent starspots, eclipses by circumstellar dust, or occultations of an accretion hotspot.

Original languageEnglish (US)
Article number48
JournalAstrophysical Journal
Issue number1
StatePublished - Oct 10 2015
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planetary systems
  • stars: individual (PTFO 8-8695)
  • stars: pre-main sequence


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