arXiv · 2407.17798
TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by TTVs
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 ($P=4.42$ 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.
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Judith Korth, Priyanka Chaturvedi, Hannu Parviainen, Ilaria Carleo, Michael Endl, Eike W. Guenther, Grzegorz Nowak, Carina Persson, Phillip J. MacQueen, Alexander J. Mustill, Juan Cabrera, William D. Cochran, Jorge Lillo-Box, David Hobbs, Felipe Murgas, Michael Greklek-McKeon, Hanna Kellermann, Guillaume Hébrard, Akihiko Fukui, Enric Pallé, Jon M. Jenkins, Joseph D. Twicken, Karen A. Collins, Samuel N. Quinn, Ján Šubjak, Paul G. Beck, Davide Gandolfi, Savita Mathur, Hans J. Deeg, David W. Latham, Simon Albrecht, David Barrado, Isabelle Boisse, Hervé Bouy, Xavier Delfosse, Olivier Demangeon, Rafael A. García, Artie P. Hatzes, Neda Heidari, Kai Ikuta, Petr Kabáth, Heather A. Knutson, John Livingston, Eder Martioli, María Morales-Calderón, Giuseppe Morello, Norio Narita, Jaume Orell-Miquel, Hanna L. M. Osborne, Dinil B. Palakkatharappil, Viktoria Pinter, Seth Redfield, Howard M. Relles, Richard P. Schwarz, Sara Seager, Avi Shporer, Marek Skarka, Gregor Srdoc, Monika Stangret, Luis Thomas, Vincent Van Eylen, Noriharu Watanabe, Joshua N. Winn. 2024-07-25. TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by TTVs. https://doi.org/10.3847/2041-8213%2Fad65fd
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