Characterizing K2 planet discoveries : a super-Earth transiting the bright K dwarf HIP 116454
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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 pR = 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.
Vanderburg , A , Montet , B T , Johnson , J A , Buchhave , L 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 , Phillip , D F , Piotto , G , Pollacco , D , Queloz , D , Rice , K , Riddle , R , Rowe , J F , Rucinski , S M , Sasselov , D , Segransan , D , Sozzetti , A , Szentgyorgyi , A , Watson , C & Weiss , W W 2015 , ' Characterizing K2 planet discoveries : a super-Earth transiting the bright K dwarf HIP 116454 ' Astrophysical Journal , vol. 800 , no. 1 , 59 . DOI: 10.1088/0004-637X/800/1/59
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