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

• Published in: arXiv.org
• Main Authors: Korth, Judith, Chaturvedi, Priyanka, Parviainen, Hannu, Carleo, Ilaria, Endl, Michael, Guenther, Eike W, Nowak, Grzegorz, Persson, Carina, 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, Eder Martioli, 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, Vincent Van Eylen, Watanabe, Noriharu, Winn, Joshua N
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 25.07.2024
• Subjects: Amplitudes; Extrasolar planets; Gas giant planets; Ground-based observation; Jupiter; Light curve; Modelling; Orbits; Physics - Earth and Planetary Astrophysics; Planet detection; Radial velocity; Satellite observation; Transit
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2407.17798

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 (\(P=4.42\) d, \(M=1.86\pm0.02\,M_\mathrm{Jup}\), \(R=2.4\pm0.5\,R_\mathrm{Jup}\)) 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 (TDVs) 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 (TESS) and ground-based facilities leads to an inner planet radius of \(2.22\pm0.06\,R_\oplus\) and mass of \(7.6\pm0.2\,M_\oplus\) 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.