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|Title:||Kepler-423b: a half-Jupiter mass planet transiting a very old solar-like star||Authors:||Gandolfi, D.
Deeg, H. J.
LANZA, Antonino Francesco
Prada Moroni, P. G.
Hatzes, A. P.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||576||First Page:||A11||Abstract:||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 ~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_star = 0.85 ± 0.04 M☉, R_star = 0.95 ± 0.04 R☉, 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_planet = 0.595 ± 0.081 M_Jup and a radius of R_planet = 1.192 ± 0.052 R_Jup, yielding a planetary bulk density of ρ_planet = 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 2σ confidence level (∆F_ec< = 14.2 ± 6.6 ppm) and found that the orbit might have a small non-zero eccentricity of 0.019^(+0.028)_(-0.014). 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.||Acknowledgments:||We are infinitely grateful to the staff members at the Nordic Optical Telescope for their valuable and unique support during the observations. We thank the editor and the anonymous referee for their careful review and very positive feedback. Davide Gandolfi thanks Gabriele Cologna for the interesting conversations on the properties of the planetary system. Hannu Parviainen has received support from the Rocky Planets Around Cool Stars (RoPACS) project during this research, a Marie Curie Initial Training Network funded by the European Commission’s Seventh Framework Programme. He has also received funding from the Väisälä Foundation through the Finnish Academy of Science and Letters and from the Leverhulme Research Project grant RPG-2012-661. Financial supports from the Spanish Ministry of Economy and Competitiveness (MINECO) are acknowledged by Hans J. Deeg for the grant AYA2012-39346-C02-02, by Sergio Hoyer for the 2011 Severo Ochoa program SEV-2011-0187, and Roi Alonso for the Ramón y Cajal program RYC-2010-06519. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission Directorate. The Kepler data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This research has made an intensive use of the Simbad database and the VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in AAS, 143, 23.||URI:||http://hdl.handle.net/20.500.12386/23931||URL:||https://www.aanda.org/articles/aa/abs/2015/04/aa25062-14/aa25062-14.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201425062||Bibcode ADS:||2015A&A...576A..11G||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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