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Measuring the orbit shrinkage rate of hot Jupiters due to tides

N. M. Rosário, S. C. C. Barros, O. Demangeon, N. C. Santos

Context. A tidal interaction between a star and a close-in exoplanet leads to shrinkage of the planetary orbit and eventual tidal dis- ruption of the planet. Measuring the shrinkage of the orbits will allow for the tidal quality parameter of the star (Q′) to be measured, which is an important parameter to obtain information about stellar interiors.

Aims. We analyse data from the Transiting Exoplanet Survey Satellite (TESS) for two targets known to host close-in hot Jupiters, which have significant data available and are expected to have a fast decay: WASP-18 and WASP-19. We aim to measure the current limits on orbital period variation and provide new constrains on Q′ for our targets.

Methods. We modelled the transit shape using all the available TESS observations and fitted the individual transit times of each tran- sit. We used previously published transit times together with our results to fit two models, a constant period model, and a quadratic orbital decay model, using Markov chain Monte Carlo (MCMC) algorithms.

Results. We obtain new constrains on Q′ for both targets and improve the precision of the known planet parameters with the newest observations from TESS. We find period change rates of (−0.11 ± 0.21) × 10−10 for WASP-18b and (−0.35 ± 0.22) × 10−10 for WASP-19b and we do not find significant evidence of orbital decay in these targets. We obtain new lower limits for Q′ of (1.42 ± 0.34) × 107 in WASP-18 and (1.26 ± 0.10) × 106 in WASP-19, corresponding to upper limits of the orbital decay rate of −0.45 × 10−10 and −0.71 × 10−10, respectively, with a 95% confidence level. We compare our results with other relevant targets for tidal decay studies.

Conclusions. We find that the orbital decay rate in both WASP-18b and WASP-19b appears to be smaller than the measured orbital decay of WASP-12b. We show that the minimum value of Q′ in WASP-18 is two orders of magnitude higher than that of WASP-12, while WASP-19 has a minimum value one order of magnitude higher, which is consistent with other similar targets. Further observations are required to constrain the orbital decay of WASP-18 and WASP-19.

planets and satellites: fundamental parameters / planets and satellites: dynamical evolution and stability / techniques: photometric / planet-star interactions

Astronomy & Astrophysics
Volume 668, Article Number A114, Number of pages 15
2022 December

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia