Mass determination of K2-19b and K2-19c from radial velocities and transit timing variations^⋆

¹ Instituto de Astrofísica de Canarias, C/vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
e-mail: dnespral@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, 38206 Tenerife, Spain
³ Dipartimento di Fisica, Università degli Studi di Trino, via Pietro Giuria 1, 10125 Torino, Italy
⁴ Landessternwarte Königstuhl, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
⁵ Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, via Marzolo 8, 35131 Padova, Italy
⁶ Leiden Observatory, University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
⁷ Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
⁸ Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung an der Universität zu Köln, Aachener Strasse 209, 50931 Köln, Germany
⁹ Stellar Astrophysics Centre, Deparment of Physics and Astronomy, Aarhus University, Ny Munkegrade 120, 8000 Aarhus C, Denmark
¹⁰ Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
¹¹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenberg, Germany
¹² Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain
¹³ Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany

Received: 4 April 2016
Accepted: 20 March 2017

Abstract

We present radial velocity follow-up observations of K2-19, a compact planetary system hosting three planets, of which the two larger ones, K2-19b and K2-19c, are close to the 3:2 mean motion resonance. An analysis considering only the radial velocity measurements detects K2-19b, the larger and more massive planet in the system, with a mass of 54.8 ± 7.5M_⊕ and provides a marginal detection of K2-19c, with a mass of M_c = 5.9^+7.6_-4.3 M_⊕. We also used the TRADES code to simultaneously model both our RV measurements and the existing transit timing measurements. We derived a mass of 54.4 ± 8.9M_⊕ for K2-19b and of 7.5^+3.0_-1.4M_⊕ for K2-19c. For K2-19b, these masses are consistent with a previous determination that was principally based on a photodynamical analysis of the K2-19 light curve. Differences remain mainly in the mass determination of the more lightweight planet, driven likely by the limited precision of the RV measurements and possibly some as yet unrecognized systematics.