TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by Transit Timing Variations

• Published in: Astrophysical journal. Letters Vol. 971; no. 2; p. L28
• Main Authors: Korth, Judith, Chaturvedi, Priyanka, Parviainen, Hannu, Carleo, Ilaria, Endl, Michael, Guenther, Eike W., Nowak, Grzegorz, Persson, Carina M., MacQueen, Phillip J., Mustill, Alexander J., Cabrera, Juan, Cochran, William D., Lillo-Box, Jorge, Hobbs, David, Murgas, Felipe, Greklek-McKeon, Michael, Kellermann, Hanna, Hébrard, Guillaume, Fukui, Akihiko, Pallé, Enric, Jenkins, Jon M., Twicken, Joseph D., Collins, Karen A., Quinn, Samuel N., Šubjak, Ján, Beck, Paul G., Gandolfi, Davide, Mathur, Savita, Deeg, Hans J., Latham, David W., Albrecht, Simon, Barrado, David, Boisse, Isabelle, Bouy, Hervé, Delfosse, Xavier, Demangeon, Olivier, García, Rafael A., Hatzes, Artie P., Heidari, Neda, Ikuta, Kai, Kabáth, Petr, Knutson, Heather A., Livingston, John, Martioli, Eder, Morales-Calderón, María, Morello, Giuseppe, Narita, Norio, Orell-Miquel, Jaume, Osborne, Hanna L. M., Palakkatharappil, Dinil B., Pinter, Viktoria, Redfield, Seth, Relles, Howard M., Schwarz, Richard P., Seager, Sara, Shporer, Avi, Skarka, Marek, Srdoc, Gregor, Stangret, Monika, Thomas, Luis, Van Eylen, Vincent, Watanabe, Noriharu, Winn, Joshua N.
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 2024; IOP Publishing
• Subjects: Amplitudes; Astronomi, astrofysik och kosmologi; Astronomy, Astrophysics and Cosmology; Exoplanet dynamics; Extrasolar planets; Fysik; Gas giant planets; Hot Jupiters; Hot Neptunes; Jupiter; Light curve; Modelling; Natural Sciences; Naturvetenskap; Orbits; Physical Sciences; Planet detection; Planets; Radial velocity; Satellite observation; Transit; Transit photometry; Transit timing variation method
• ISSN: 2041-8205; 2041-8213; 2041-8213
• DOI: 10.3847/2041-8213/ad65fd

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 M Jup , R = 2.4 ± 0.5 R Jup ) 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.