HAT-P-31b,c: A transiting, eccentric, hot Jupiter and a long-period, massive third body

D. M. Kipping, J. Hartman, G. Á Bakos, G. Torres, D. W. Latham, D. Bayliss, L. L. Kiss, B. Sato, B. Béky, Géza Kovcs, S. N. Quinn, L. A. Buchhave, J. Andersen, G. W. Marcy, A. W. Howard, D. A. Fischer, J. A. Johnson, R. W. Noyes, D. D. Sasselov, R. P. StefanikJ. Lázár, I. Papp, P. Sári, G. Frész

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


We report the discovery of HAT-P-31b, a transiting exoplanet orbiting the V = 11.660 dwarf star GSC 2099-00908. HAT-P-31b is the first planet discovered with the Hungarian-made Automated Telescope (HAT) without any follow-up photometry, demonstrating the feasibility of a new mode of operation for the HATNet project. The 2.17MJ , 1.1RJ planet has a period of Pb = 5.0054days and maintains an unusually high eccentricity of eb = 0.2450 ± 0.0045, determined through Keck, FIbr-fed chelle Spectrograph, and Subaru high-precision radial velocities (RVs). Detailed modeling of the RVs indicates an additional quadratic residual trend in the data detected to very high confidence. We interpret this trend as a long-period outer companion, HAT-P-31c, of minimum mass 3.4MJ and period ≥2.8years. Since current RVs span less than half an orbital period, we are unable to determine the properties of HAT-P-31c to high confidence. However, dynamical simulations of two possible configurations show that orbital stability is to be expected. Further, if HAT-P-31c has non-zero eccentricity, our simulations show that the eccentricity of HAT-P-31b is actively driven by the presence of c, making HAT-P-31 a potentially intriguing dynamical laboratory.

Original languageEnglish (US)
Article number95
JournalAstronomical Journal
Issue number3
StatePublished - Sep 2011
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planetary systems
  • stars: individual (HAT-P-31, GSC 2099-00908)
  • techniques: photometric
  • techniques: spectroscopic


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