Exoplanets, -moons, -comets

Long-term Monitoring Of WASP-19 b: Signs Of Apsidal Precession And Molecular Signatures

By Keith Cowing
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astro-ph.EP
March 17, 2026
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Long-term Monitoring Of WASP-19 b: Signs Of Apsidal Precession And Molecular Signatures
Variation of the planetary radius, expressed as transit depth, as a function of wavelength. Sky-blue points correspond to DanishDFOSC (this work), lime to TESS (this work), orange to GROND (Mancini et al. 2013), crimson to MMIRS (Bean et al. 2013), green to (Sedaghati et al. 2015a), and black to (Huitson et al. 2013). Vertical error bars represent measurement uncertainties, while horizontal bars indicate the full width half maximum (FWHM) of the respective passbands. Synthetic photometric points were computed using the SVO SpecPhot tool to obtain flux-weighted transit depths at the effective wavelengths of the UV–optical filters. Retrievals were performed with POSEIDON including the opacities of Na, K, TiO, VO, and H2O. The orange curve shows the median best-fit model excluding TiO and VO, with 1σ and 2σ confidence intervals. The purple curve shows the median best-fit model including TiO and VO, with corresponding uncertainties. See Sect. 6.2 for details. — astro-ph.EP

With more than 6000 exoplanets discovered so far, about 12 percent are hot Jupiters. Their large sizes and short orbital periods make them valuable targets for studying planetary formation, atmospheres, and orbital evolution.

We present a homogeneous analysis of the WASP-19 b system using a 15 year dataset to investigate both its orbital dynamics and atmospheric properties. We test whether the transit times show evidence for tidal orbital decay, apsidal precession, or periodic perturbations from an additional body, and we also construct a photometric transmission spectrum.

Multi-wavelength light curves are modeled with PRISM to account for starspots, and linear, quadratic, and cubic ephemeris models are fitted to the transit timing residuals. Our dataset includes 27 new transits and reveals no statistically significant periodic signal.

Although none of the tested models fully reproduces the timing scatter, the transit times show systematic deviations from a constant period and are best described by the cubic ephemeris, indicating a slow long-term trend over the full baseline.

This behavior is more consistent with gradual apsidal precession than with monotonic tidal decay. A precession model yields a rate of 1.00 +/- 0.12 x 10^-4 rad per orbit and a planetary Love number k2p = 0.107 +/- 0.08. The transmission spectrum shows signatures of Na, K, and H2O, with no strong evidence for TiO or VO.

These results suggest that apsidal precession may dominate the long-term orbital evolution of WASP-19 b. Continued high-precision timing and spectroscopic observations are needed to further test this scenario.

A. R. Rajkumar, A. Bayo, P. Peng, J. Tregloan-Reed, J. Southworth, Tobias C. Hinse, L. G. Alegre, F. Amadio, M. Andersen, N. Bach-Møller, M. Basilicata, M. Bonavita, V. Bozza, M. J. Burgdorf, R. E. Cannon, G. Columba, M. Dominik, A. Donaldson, R. Figuera Jaimes, J. Fynbo, M. Hundertmark, U. G. Jørgensen, E. Khalouei, H. Korhonen, P. Longa-Peña, M. Rabus, S. Rahvar, H. Rendell-Bhatti, P. Rota, A. Rożek, S. Sajadian, J. Skottfelt, C. Snodgrass

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2603.12395 [astro-ph.EP] (or arXiv:2603.12395v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2603.12395
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Related DOI:
https://doi.org/10.1051/0004-6361/202556822
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Submission history
From: Anitha Raj Rajkumar Ms.
[v1] Thu, 12 Mar 2026 19:14:10 UTC (4,343 KB)
https://arxiv.org/abs/2603.12395
Astrobiology, Astrochemistry,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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