Characterizing K2 Planet Discoveries: A super-Earth transiting the bright K-dwarf HIP 116454

TL;DR

This paper reports the discovery and characterization of a super-Earth exoplanet, HIP 116454 b, orbiting a bright K-dwarf star, using K2 photometry, radial velocity measurements, and follow-up observations, demonstrating a new analysis technique for K2 data.

Contribution

It introduces a novel K2 photometric analysis method that corrects for telescope drifts, enabling the detection of a transiting super-Earth in a short observation window.

Findings

Discovered a super-Earth with a radius of 2.53 Earth radii.

Confirmed the planet's mass as approximately 11.82 Earth masses.

Demonstrated the effectiveness of new K2 data correction techniques.

Abstract

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] = -.16 +/- .18, and has a radius R = 0.716 +/- .0024 R_sun and mass M = .775 +/- .027 Msun. The star was observed by the Kepler spacecraft during its Two-Wheeled Concept Engineering Test in February 2014. 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 Rearth. Radial velocity observations with the HARPS-N spectrograph reveal a 11.82 +/- 1.33 Mearth 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.