Characterizing K2 Planet Discoveries: A Super-Earth Transiting the Bright K Dwarf HIP 116454

Vanderburg, A.
Montet, B.T.
Johnson, J.A.
Zeng, L.
Pepe, F.
Cameron, A.C.
Latham, D.W.
Molinari, E.
Udry, S.
Lovis, C.
Matthews, J.M.
Cameron, C.
Law, N.
Bowler, B.P.
Angus, R.
Baranec, C.
Bieryla, A.
Boschin, W.
Charbonneau, D.
Cosentino, R.
Dumusque, X.
Figueira, P.
Guenther, D.B.
Harutyunyan, A.
Hellier, C.
Kuschnig, R.
Lopez-Morales, M.
Mayor, M.
Micela, G.
Moffat, A.F.J.
Pedani, M.
Phillips, D.F.
Piotto, G.
Pollacco, P.
Queloz, D.
Rice, K.
Riddle, R.
Rowe, J.F.
Rucinski, S.M.
Sasselov, D.D.
Ségransan, D.
Sozzetti, A.
Szentgyorgyi, A.
Watson, C.
Weiss, W.W.
Astrophysical Journal, 800, 59

We report the first planet discovery from the two-wheeled Kepler (K2) mission: HIP 116454 b. The host star HIP 116454 is a bright (V= 10.1, K = 8.0) K1 dwarf with high proper motion and a parallax-based distance of 55.2 ± 5.4 pc. Based on high-resolution optical spectroscopy, we find that the host star is metal-poor with [Fe/H] =–0.16 ± 0.08 and has a radius R= 0.716 ± 0.024 R and mass M= 0.775 ± 0.027 M. The star was observed by the Kepler spacecraft during its Two-Wheeled Concept Engineering Test in 2014 February. During the 9 days of observations, K2 observed a single transit event. Using a new K2 photometric analysis technique, we are able to correct small telescope drifts and recover the observed transit at high confidence, corresponding to a planetary radius of Rp = 2.53 ± 0.18 R. Radial velocity observations with the HARPS-N spectrograph reveal a 11.82 ± 1.33 M⊕ planet in a 9.1 day orbit, consistent with the transit depth, duration, and ephemeris. Follow-up photometric measurements from the MOST satellite confirm the transit observed in the K2 photometry and provide a refined ephemeris, making HIP 116454 b amenable for future follow-up observations of this latest addition to the growing population of transiting super-Earths around nearby, bright stars.