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

TL;DR

This study combines radial velocity and transit timing variation data to accurately determine the masses of the planets K2-19b and K2-19c, confirming previous estimates for K2-19b and providing new insights into K2-19c.

Contribution

It presents a combined RV and TTV analysis for mass determination of K2-19 planets, improving accuracy and consistency over previous methods.

Findings

K2-19b mass: approximately 54.8 M⊕ from RV data.

K2-19c mass: marginal detection at about 5.9 M⊕ from RV, more precise at 7.5 M⊕ with combined analysis.

Results are consistent with previous photodynamical estimates for K2-19b.

Abstract

We present FIES@NOT, HARPS-N@TNG, and HARPS@ESO-3.6m radial velocity follow-up observations of K2-19, a compact planetary system hosting three planets, of which the two larger ones, namely 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 largest and most massive planet in the system, with a mass of $54.8\pm7.5$~M${_\oplus}$ and provides a marginal detection of K2-19c, with a mass of M$_\mathrm{c}$=$5.9^{+7.6}_{-4.3}$ M$_\oplus$. We also used the TRADES code to simultaneously model both our RV measurements and the existing transit-timing measurements. We derived a mass of $54.4\pm8.9$~M${_\oplus}$ for K2-19b and of $7.5^{+3.0}_{-1.4}$~M${_\oplus}$ for K2-19c. A prior K2-19b mass estimated by Barros et al. 2015, based principally on a photodynamical analysis of K2-19's light-curve, is consistent with both analysis, our combined TTV and RV analysis, and with our analysis based purely on RV measurements. Differences remain mainly in the errors of the more lightweight planet, driven likely by the limited precision of the RV measurements and possibly some yet unrecognized systematics.