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


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 A11

Subject Categories

Astronomy, Astrophysics and Cosmology



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