Kepler-423b: a half-Jupiter mass planet transiting a very old solar-like star
Journal article, 2015
We report the spectroscopic confirmation of the Kepler object of interest KOI-183.01 (Kepler-423b), 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 light curve of Kepler-423 exhibits quarter-to-quarter systematic variations of the transit depth, with a peak-to-peak amplitude of similar to 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 Kepler-423 is a G4 dwarf with M-* = 0.85 +/- 0.04 M-circle dot, R-* = 0.95 +/- 0.04 R-circle dot, T-eff = 5560 +/- 80 K, [M/H] = -0.10 +/- 0.05 dex, and with an age of 11 +/- 2 Gyr. The planet Kepler-423b has a mass of M-p = 0.595 +/- 0.081 M-Jup and a radius of R-p = 1.192 +/- 0.052 R-Jup, yielding a planetary bulk density of rho(p) = 0.459 +/- 0.083 g cm(-3). The radius of Kepler-423b 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 sigma confidence level (Delta F-ec = 14.2 +/- 6.6 ppm) and found that the orbit might have a small non-zero eccentricity of 0.019(-0.014)(+0.028) . With a Bond albedo of A(B) = 0.037 +/- 0.019, Kepler-423b is one of the gas-giant planets with the lowest albedo known so far.
techniques: radial velocities
planets and satellites: detection
planets and satellites: individual: Kepler-423b
planets and satellites: fundamental parameters
techniques: photometric
stars: fundamental parameters
Author
D. Gandolfi
Istituto nazionale di astrofisica (INAF)
Heidelberg-Königstuhl State Observatory
H. Parviainen
University of Oxford
H. J. Deeg
University of La Laguna
Instituto de Astrofísica de Canarias
A. F. Lanza
Istituto nazionale di astrofisica (INAF)
Malcolm Fridlund
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
P. G. P. Moroni
University of Pisa
R. Alonso
Instituto de Astrofísica de Canarias
University of La Laguna
T. Augusteijn
J. Cabrera
German Aerospace Center (DLR)
T. Evans
University of Oxford
S. Geier
A. Hatzes
T. Holczer
Tel Aviv University
S. Hoyer
University of La Laguna
Instituto de Astrofísica de Canarias
T. Kangas
Tuorla Observatory
T. Mazeh
Tel Aviv University
I. Pagano
Istituto nazionale di astrofisica (INAF)
L. Tal-Or
Tel Aviv University
B. Tingley
Aarhus University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 576 A11Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201425062