HAT-P-67b: An Extremely Low Density Saturn Transiting an F-subgiant Confirmed via Doppler Tomography

G. Zhou, G. Bakos, J. D. Hartman, D. W. Latham, G. Torres, W. Bhatti, K. Penev, L. Buchhave, G. Kovács, A. Bieryla, S. Quinn, H. Isaacson, B. J. Fulton, E. Falco, Z. Csubry, M. Everett, T. Szklenar, G. Esquerdo, P. Berlind, M. L. CalkinsB. Béky, R. P. Knox, P. Hinz, E. P. Horch, L. Hirsch, S. B. Howell, R. W. Noyes, G. Marcy, M. De Val-Borro, J. Lázár, I. Papp, P. Sári

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33 Scopus citations


We report the discovery of HAT-P-67b, which is a hot-Saturn transiting a rapidly rotating F-subgiant. HAT-P-67b has a radius of Rp=2.085 -0.071 +0.096 RJ, and orbites a M∗ = 1.642-0.072 +0.155 M, R = 2.546-0.099 +0.0084 R host star in a ∼4.81 day period orbit. We place an upper limit on the mass of the planet via radial velocity measurements to be Mp < 0.59 MJ, and a lower limit of >0.056 MJ by limitations on Roche lobe overflow. Despite being a subgiant, the host star still exhibits relatively rapid rotation, with a projected rotational velocity of v sin I = 35.8 ±1.1 km s-1, which makes it difficult to precisely determine the mass of the planet using radial velocities. We validated HAT-P-67b via two Doppler tomographic detections of the planetary transit, which eliminate potential eclipsing binary blend scenarios. The Doppler tomographic observations also confirm that HAT-P-67b has an orbit that is aligned to within 12, in projection, with the spin of its host star. HAT-P-67b receives strong UV irradiation and is among one of the lowest density planets known, which makes it a good candidate for future UV transit observations in the search for an extended hydrogen exosphere.

Original languageEnglish (US)
Article number211
JournalAstronomical Journal
Issue number5
StatePublished - May 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planetary systems
  • stars: individual (HAT-P-67)
  • techniques: photometric
  • techniques: spectroscopic


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