J. Korth, P. Chaturvedi, H. Parviainen, I. Carleo, M. Lendl, E. W. Guenther, G. Nowak, C. M. Persson, P. J. MacQueen, A. J. Mustill, J. Cabrera, W. D. Cochran, J. Lillo-Box, D. Hobbs, F. Murgas, M. Greklek-McKeon, H. Kellermann, G. Hébrard, A. Fukui, E. Pallé, J. M. Jenkins, J. D. Twicken, K. A. Collins, S. N. Quinn, J. Subjak, P. G. Beck, D. Gandolfi, S. Mathur, H. J. Deeg, D. W. Latham, S. Albrecht, D. Barrado, I. Boisse, H. Bouy, X. Delfosse, O. Demangeon, R. A. Garcia, A. P. Hatzes, N. Heidari, K. Ikuta, P. Kabáth, H. A. Knutson, J. H. Livingston, E. Martioli, M. Morales-Calderón, G. Morello, N. Narita, J. Orell-Miquel, H. L. M. Osborne, D. B. Palakkatharappil, V. Pintėr, S. Redfield, H. Relles, R. P. Schwarz, S. Seager, A. Shporer, M. Skarka, G. Srdoc, M. Stangret, L. Thomas, V. Van Eylen, N. Watanabe, J. N. Winn
Abstract
We report the discovery and characterization of a small planet, TOI-1408 c, on a 2.2 day orbit located interior to a previously known hot Jupiter, TOI-1408 b (P = 4.42 days, M = 1.86 ± 0.02 MJup, R = 2.4 ± 0.5 RJup) that exhibits grazing transits. The two planets are near 2:1 period commensurability, resulting in significant transit timing variations (TTVs) for both planets and transit duration variations for the inner planet. The TTV amplitude for TOI-1408 c is 15% of the planet's orbital period, marking the largest TTV amplitude relative to the orbital period measured to date. Photodynamical modeling of ground-based radial velocity (RV) observations and transit light curves obtained with the Transiting Exoplanet Survey Satellite and ground-based facilities leads to an inner planet radius of 2.22 ± 0.06 R⊕ and mass of 7.6 ± 0.2 M⊕ that locates the planet into the sub-Neptune regime. The proximity to the 2:1 period commensurability leads to the libration of the resonant argument of the inner planet. The RV measurements support the existence of a third body with an orbital period of several thousand days. This discovery places the system among the rare systems featuring a hot Jupiter accompanied by an inner low-mass planet.
Keywords
Exoplanet dynamics; Hot Jupiters; Hot Neptunes; Transit timing variation method; Transit photometry; Radial velocity
The Astrophysical Journal Letters
Volume 971, Number 2
2024 September
