Hoyer, S, Bonfanti, A, Leleu, A, Acuna, L, Serrano, LM, Deleuil, M, Bekkelien, A, Broeg, C, Floren, H-G, Queloz, D, Wilson, TG, Sousa, SG, Hooton, MJ, Adibekyan, V, Alibert, Y, Alonso, R, Anglada, G, Asquier, J, Barczy, T, Barrado, D, Barros, SCC, Baumjohann, W, Beck, M, Beck, T, Benz, W, Billot, N, Biondi, F, Bonfils, X, Brandeker, A, Cabrera, J, Charnoz, S, Cameron, AC, Csizmadia, S, Davies, MB, Delrez, L, Demangeon, ODS, Demory, B-O, Ehrenreich, D, Erikson, A, Fortier, A, Fossati, L, Fridlund, M, Gandolfi, D, Gillon, M, Guedel, M, Hara, N, Heng, K, Isaak, KG, Jenkins, JM, Kiss, LL, Laskar, J, Latham, DW, des Etangs, AL, Lendl, M, Lovis, C, Luntzer, A, Magrin, D, Maxted, PFL, Nascimbeni, V, Olofsson, G, Ottensamer, R, Pagano, I, Palle, E, Persson, CM, Peter, G, Piazza, D, Piotto, G, Pollacco, D, Ragazzoni, R, Rando, N, Rauer, H, Ribas, I, Ricker, GR, Salmon, S, Santos, NC, Scandariato, G, Seager, S, Segransan, D, Simon, AE, Smith, AMS, Steller, M, Szabo, GM, Thomas, N, Twicken, JD, Udry, S, Van Grootel, V, Vanderspek, RK, Walton, NA, Westerdorff, K and Winn, JN (2022) Characterization of the HD 108236 system with CHEOPS and TESS Confirmation of a fifth transiting planet. Astronomy & Astrophysics, 668 (A117). ISSN 0004-6361

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Context. The HD 108236 system was first announced with the detection of four small planets based on TESS data. Shortly after, the transit of an additional planet with a period of 29.54 d was serendipitously detected by CHEOPS. In this way, HD 108236 (V = 9.2) became one of the brightest stars known to host five small transiting planets (Rp < 3 R⊕).

Aims. We characterize the planetary system by using all the data available from CHEOPS and TESS space missions. We use the flexible pointing capabilities of CHEOPS to follow up the transits of all the planets in the system, including the fifth transiting body.

Methods. After updating the host star parameters by using the results from Gaia eDR3, we analyzed 16 and 43 transits observed by CHEOPS and TESS, respectively, to derive the planets’ physical and orbital parameters. We carried out a timing analysis of the transits of each of the planets of HD 108236 to search for the presence of transit timing variations.

Results. We derived improved values for the radius and mass of the host star (R★ = 0.876 ± 0.007 R0 and M★ = 0.867-0.046+0.047M⊙). We confirm the presence of the fifth transiting planet f in a 29.54 d orbit. Thus, the HD 108236 system consists of five planets of Rb = 1.587±0.028, Rc = 2.122±0.025, Rd = 2.629 ± 0.031, Re = 3.008 ± 0.032, and Rf = 1.89 ± 0.04 [R⊕]. We refine the transit ephemeris for each planet and find no significant transit timing variations for planets c, d, and e. For planets b and f, instead, we measure significant deviations on their transit times (up to 22 and 28 min, respectively) with a non-negligible dispersion of 9.6 and 12.6 min in their time residuals.

Conclusions. We confirm the presence of planet f and find no significant evidence for a potential transiting planet in a 10.9 d orbital period, as previously suggested. Further monitoring of the transits, particularly for planets b and f, would confirm the presence of the observed transit time variations. HD 108236 thus becomes a key multi-planetary system for the study of formation and evolution processes. The reported precise results on the planetary radii – together with a profuse RV monitoring – will allow for an accurate characterization of the internal structure of these planets.

Item Type: Article
Additional Information: Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe-to-Open model. Subscribe to A&A to support open access publication.
Uncontrolled Keywords: planetary systems; planets and satellites: detection; planets and satellites: fundamental parameters; planets and satellites: individual: HD 108236; planets and satellites: individual: TOI 1233
Subjects: Q Science > Q Science (General)
Q Science > QB Astronomy
Q Science > QB Astronomy > QB600 Planets. Planetology
Q Science > QB Astronomy > QB799 Stars
Related URLs:
Depositing User: Symplectic
Date Deposited: 16 Mar 2023 10:23
Last Modified: 16 Mar 2023 11:21
URI: https://eprints.keele.ac.uk/id/eprint/12019

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