TS23/McDonald and FIES/NOT strike again: Two new warm Jupiter systems and outer companions in a third

October 2026 • 2026A&A...714A.496K

Authors • Knudstrup, E. • Gandolfi, D. • Cochran, W. D. • Endl, M. • MacQueen, P. • Pugh, T. • Lundkvist, M. S. • Persson, C. M. • Stokholm, A. • Winther, M. L. • Larsen, J. R. • Rørsted, J. L. • Albrecht, S. H. • Collins, K. A. • Watkins, C. • Edwards, B. • Ciardi, D. R. • Clark, C. A. • Polanski, A. S. • Ziegler, C. • Briceño, C. • Mann, A. W. • Everett, M. • Howell, S. • Safonov, B. • Gan, T. • Barkaoui, K. • Benni, P. • Schwarz, R. P. • Horne, K. • Sefako, R. • Muthukrishna, D.

Abstract • Context. Gas giant planets with orbital periods of P~8--200 d, known as warm Jupiters, are thought to be largely unaffected by the tidal interactions that can often erase valuable information on the dynamical histories of hot Jupiters. Their orbital eccentricities (e) and stellar obliquities are therefore expected to be preserved, making them valuable probes of giant-planet formation and migration. Aims. Our aim is to identify and characterise transiting warm Jupiters and expand the sample of well-characterised systems and enable further studies of giant-planet formation and migration. Methods. We analysed TESS transit photometry, together with ground-based radial velocity (RV) measurements. We performed a joint fit of the photometric and spectroscopic data from the TS23 and FIES spectrographs to determine the planetary and orbital parameters. Results. We report on the discovery and characterisation of two new, transiting warm Jupiters; TOI-5120 b (M_p = 1.23 ± 0.05 M_J, R_p = 0.969 ± 0.017 R_J, P = 24.91645 ± 0.00002 d, e = 0.10 ± 0.02) and TOI-5699 b (M_p = 0.25 ± 0.03 M_J, R_p = 0.996 ± 0.015 R_J, P = 22.01850 ± 0.00004 d, e = 0.30_-0.08^+0.09). We also refined the parameters of the known warm Jupiter TOI-2158 b (M_p = 0.87 ± 0.04 M_J, R = 0.899 ± 0.015 R_J, P = 8.60079_-0.00001^+0.00002 d, e = 0.028_-0.014^+0.013). In addition, we detected an outer planetary companion, TOI-2158 c (M_p sin i = 1.62 ± 0.13 M_J, P = 414.5_-1.6^+1.5 d, e = 0.54 ± 0.04), and identified a long-term RV trend that could indicate another planetary companion on a wide orbit. Conclusions. The diverse architectures of these systems, particularly the presence and absence of outer companions, highlight the range of dynamical pathways leading to warm Jupiters.

Links

• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202661610/postscript
• PDF https://www.aanda.org/10.1051/0004-6361/202661610/pdf
• PREPRINT http://arxiv.org/abs/2609.30915
• DATA https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/714/A496
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202661610