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