Transiting planet candidate from K2 with the longest period

H. A. C. Giles, H. P. Osborn, S. Blanco-Cuaresma, C. Lovis, D. Bayliss, P. Eggenberger, A. Collier Cameron, M. H. Kristiansen, O. Turner, F. Bouchy, S. Udry

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


Context. We present the transit and follow-up of a single transit event from Campaign 14 of K2, EPIC248847494b, which has a duration of 54 h and a 0.18% depth.

Aims. Using photometric tools and conducting radial velocity follow-up, we vet and characterise this very strong candidate.

Methods. Owing to the long, unknown period, standard follow-up methods needed to be adapted. The transit was fitted using Namaste, and the radial velocity slope was measured and compared to a grid of planet-like orbits with varying masses and periods. These used stellar parameters measured from spectra and the distance as measured by Gaia.

Results. Orbiting around a sub-giant star with a radius of 2.70 ± 0.12 RSol, the planet has a radius of 1.11−0.07+0.07 RJup and a period of 3650−1130+1280 days. The radial velocity measurements constrain the mass to be lower than 13 MJup, which implies a planet-like object.

Conclusions. We have found a planet at 4.5 AU from a single-transit event. After a full radial velocity follow-up campaign, if confirmed, it will be the longest-period transiting planet discovered.
Original languageEnglish
Article numberL13
Number of pages5
JournalAstronomy & Astrophysics
Publication statusPublished - 20 Jul 2018


  • Planets and satellites: detection
  • Stars: individual: EPIC248847494
  • Planetary systems
  • Techniques: photometric
  • Techniques: radial velocities
  • Techniques: spectroscopic


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