Doppler Monitoring of five K2 Transiting Planetary Systems

Doppler Monitoring of five K2 Transiting Planetary Systems

Authors:

Dai et al

Abstract:

In an effort to measure the masses of planets discovered by the NASA {\it K2} mission, we have conducted precise Doppler observations of five stars with transiting planets. We present the results of a joint analysis of these new data and previously published Doppler data. The first star, an M dwarf known as K2-3 or EPIC~201367065, has three transiting planets ("b", with radius 2.1 R⊕; "c", 1.7 R⊕; and "d", 1.5 R⊕). Our analysis leads to the mass constraints: Mb=8.1+2.0−1.9 M⊕ and Mc less than 4.2 M⊕~(95\%~conf.). The mass of planet d is poorly constrained because its orbital period is close to the stellar rotation period, making it difficult to disentangle the planetary signal from spurious Doppler shifts due to stellar activity. The second star, a G dwarf known as K2-19 or EPIC~201505350, has two planets ("b", 7.7 R⊕; and "c", 4.9 R⊕) in a 3:2 mean-motion resonance, as well as a shorter-period planet ("d", 1.1 R⊕). We find Mb= 28.5+5.4−5.0 M⊕, Mc= 25.6+7.1−7.1 M⊕ and Md less than 14.0 M⊕~(95\%~conf.). The third star, a G dwarf known as K2-24 or EPIC~203771098, hosts two transiting planets ("b", 5.7 R⊕; and "c", 7.8 R⊕) with orbital periods in a nearly 2:1 ratio. We find Mb= 19.8+4.5−4.4 M⊕ and Mc = 26.0+5.8−6.1 M⊕.

EPIC 204129699b: a new hot Jupiter in a 1.26 day orbit

EPIC 204129699b, a grazing transiting hot Jupiter on an 1.26-day orbit around a bright solar like star

Authors:

Grziwa et al

Abstract:

We report the discovery of EPIC 204129699b, the first confirmed transiting hot Jupiter detected by the K2 space mission. We combined K2 photometry with FastCam lucky imaging and FIES and HARPS high-resolution spectroscopy to confirm the planetary nature of the transiting object and derived the system parameters. EPIC 204129699b is a 1.8-Jupiter-mass planet on an 1.26-day-orbit around a G7V star (M* = 0.91 Msun, R* = 0.78 Rsun). The planetary radius is poorly constrained (0.7 less than Rp less than 1.4 RJup ), owing to the grazing transit and the low sampling rate of the K2 photometry. The short orbital period and the brightness of the host star (V = 10.8 mag) make the system amenable to atmospheric characterization.