Transiting exoplanets from the CoRoT space mission

XXIX. The hot Jupiters CoRoT-30 b and CoRoT-31 b^★

¹ Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
e-mail: pascal.borde@u-bordeaux.fr
² Observatoire astronomique de l’Université de Genève, 51 ch. des Maillettes, 1290 Versoix, Switzerland
³ Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales. Buenos Aires, Argentina
⁴ CONICET – Universidad de Buenos Aires. Instituto de Astronomía y Física del Espacio (IAFE). Buenos Aires, Argentina
⁵ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
⁶ Institut d’astrophysique spatiale, Univ. Paris-Sud, CNRS, 91405 Orsay, France
⁷ Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
⁸ Dipartimento di Fisica, Universitá di Torino, via P. Giuria 1, 10125 Torino, Italy
⁹ Landessternwarte Königstuhl, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
¹⁰ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹¹ Universidad de La Laguna, Dept. de Astrofísica, 38206 La Laguna, Tenerife, Spain
¹² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹³ Leiden Observatory, University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
¹⁴ Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
¹⁵ Department of Physics, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH, UK
¹⁶ Aix Marseille Univ, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France
¹⁷ LESIA, Observatoire de Paris, Univ. Pierre & Marie Curie, Univ. Paris-Diderot, CNRS, 5 place J. Janssen, 92195 Meudon, France
¹⁸ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
¹⁹ INAF-Osservatorio Astrofisico di Torino Strada Osservatorio, 20 10025 Pino Torinese (TO), Italy
²⁰ Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
²¹ IAG-Universidade de São Paulo, 1226 Sâo Paulo, Brasil
²² Thüringer Landessternwarte, Sternwarte 5, Tautenburg 5, 07778 Tautenburg, Germany
²³ Rheinisches Institut für Umweltforschung an der Universität zu Köln, 50931 Aachener Strasse 209, Germany
²⁴ Institut d’astrophysique de Paris, Univ. Pierre & Marie Curie, CNRS, 98 bis boulevard Arago, 75014 Paris, France
²⁵ School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, 39040 Tel Aviv University, Tel Aviv, Israel
²⁶ Sub-department of Astrophysics, Department of Physics, University of Oxford, Oxford, OX1 3RH, UK
²⁷ Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
²⁸ LUTH, Observatoire de Paris, Univ. Paris-Diderot, CNRS, 5 place Jules Janssen, 92195 Meudon, France
²⁹ Kuffner Observatory, Johann-Staud-Straße 10, 1160 Vienna, Austria

Received: 1 December 2017
Accepted: 1 September 2019

Abstract

Aims. We report the discovery as well as the orbital and physical characterizations of two new transiting giant exoplanets, CoRoT-30 b and CoRoT-31 b, with the CoRoT space telescope.

Methods. We analyzed two complementary data sets: photometric transit light curves measured by CoRoT, and radial velocity curves measured by the HARPS spectrometer. To derive the absolute masses and radii of the planets, we modeled the stars from available magnitudes and spectra.

Results. We find that CoRoT-30 b is a warm Jupiter on a close-to-circular 9.06-day orbit around a G3V star with a semi-major axis of about 0.08 AU. It has a radius of 1.01 ± 0.08 R_J, a mass of 2.90 ± 0.22 M_J, and therefore a mean density of 3.45 ± 0.65 g cm⁻³. The hot Jupiter CoRoT-31 b is on a close-to-circular 4.63-day orbit around a G2 IV star with a semi-major axis of about 0.05 AU. It has a radius of 1.46 ± 0.30 R_J, a mass of 0.84 ± 0.34 M_J, and therefore a mean density of 0.33 ± 0.18 g cm⁻³.

Conclusions. Neither system seems to support the claim that stars hosting planets are more depleted in lithium. The radii of both planets are close to that of Jupiter, but they differ in mass; CoRoT-30 b is ten times denser than CoRoT-31 b. The core of CoRoT-30 b would weigh between 15 and 75 Earth masses, whereas relatively weak constraints favor no core for CoRoT-31 b. In terms of evolution, the characteristics of CoRoT-31 b appear to be compatible with the high-eccentricity migration scenario, which is not the case for CoRoT-30 b. The angular momentum of CoRoT-31 b is currently too low for the planet to evolve toward synchronization of its orbital revolution with stellar rotation, and the planet will slowly spiral-in while its host star becomes a red giant. CoRoT-30 b is not synchronized either: it looses angular momentum owing to stellar winds and is expected reach steady state in about 2 Gyr. CoRoT-30 and 31, as a pair, are a truly remarkable example of diversity in systems with hot Jupiters.