Kepler-424 (KOI-214) b-c & KOI-183 b

Two more Kepler objects of interest with confirmed exoplanetary systems:

Kepler-424 b: A "Lonely" Hot Jupiter That Found A Companion

Quote :

Hot Jupiter systems provide unique observational constraints for migration models in multiple systems and binaries. We report on the discovery of the Kepler-424 (KOI-214) two-planet system, which consists of a transiting hot Jupiter (Kepler-424b) in a 3.31-d orbit accompanied by a more massive outer companion in an eccentric (e=0.3) 223-d orbit. The outer giant planet, Kepler-424c, is not detected to transit the host star. The masses of both planets and the orbital parameters for the second planet were determined using precise radial velocity (RV) measurements from the Hobby-Eberly Telescope (HET) and its High Resolution Spectrograph (HRS). In stark contrast to smaller planets, hot Jupiters are predominantly found to be lacking any nearby additional planets, the appear to be "lonely" (e.g. Steffen et al.~2012). This might be a consequence of a highly dynamical past of these systems. The Kepler-424 planetary system is a system with a hot Jupiter in a multiple system, similar to upsilon Andromedae. We also present our results for Kepler-422 (KOI-22), Kepler-77 (KOI-127; Gandolfi et al.~2013), Kepler-43 (KOI-135; Bonomo et al.~2012), and Kepler-423 (KOI-183). These results are based on spectroscopic data collected with the Nordic Optical Telescope (NOT), the Keck 1 telescope and HET. For all systems we rule out false positives based on various follow-up observations, confirming the planetary nature of these companions. We performed a comparison with planetary evolutionary models which indicate that these five hot Jupiters have a heavy elements content between 20 and 120 M_Earth.

KOI-183b*: a half-Jupiter mass planet transiting a very old solar-like star

Quote :

We report the spectroscopic confirmation of the Kepler object of interest KOI-183b (also known as KOI-183.01), a half-Jupiter mass planet transiting an old solar-like star every 2.7 days. Our analysis is the first to combine the full Kepler photometry (quarters 1-17) with high-precision radial velocity measurements taken with the FIES spectrograph at the Nordic Optical Telescope. We simultaneously modelled the photometric and spectroscopic data-sets using Bayesian approach coupled with Markov chain Monte Carlo sampling. We found that the Kepler pre-search data conditioned (PDC) light curve of KOI-183 exhibits quarter-to-quarter systematic variations of the transit depth, with a peak-to-peak amplitude of about 4.3 % and seasonal trends reoccurring every four quarters. We attributed these systematics to an incorrect assessment of the quarterly variation of the crowding metric. The host star KOI-183 is a G4 dwarf with M⋆=0.85±0.04 MSun, R⋆=0.95±0.04 RSun, Teff=5560±80 K, [M/H]=−0.10±0.05 dex, and with an age of 11±2 Gyr. The planet KOI-183b has a mass of Mp=0.595±0.081 MJup and a radius of Rp=1.192±0.052 RJup, yielding a planetary bulk density of ρp=0.459±0.083 g/cm3. The radius of KOI-183b is consistent with both theoretical models for irradiated coreless giant planets and expectations based on empirical laws. The inclination of the stellar spin axis suggests that the system is aligned along the line of sight. We detected a tentative secondary eclipse of the planet at a 2-σ confidence level (ΔFec=14.2±6.6 ppm) and found that the orbit might have a small non-zero eccentricity of e=0.019+0.028−0.014. With a Bond albedo of AB=0.037±0.019, KOI-183b is one of the gas-giant planets with the lowest albedo known so far.

(*) = KOI-183 = Kepler-423