Hints of a close outer companion to the ultra-hot Jupiter TOI-2109 b

Context . Hot Jupiters (HJs) with close-by planetary companions are rare, with only a handful of them having been discovered so far. This could be due to their suggested dynamical histories, which lead to the possible ejection of other planets. TOI-2109 b is special in this regard because it is the HJ with the closest relative separation from its host star, being separated by less than 2.3 stellar radii. Unexpectedly, transit timing measurements from recently obtained CHEOPS observations show low-amplitude transit-timing variations (TTVs). Aims . We aim to search for signs of orbital decay and to characterise the apparent TTVs in an attempt to gain information about a possible companion. Methods . We fitted the newly obtained CHEOPS light curves using TLCM and extracted the resulting mid-transit timings. Successively, we used these measurements in combination with TESS and archival photometric data and radial velocity (RV) data to estimate the rate of tidal orbital decay of TOI-2109 b, and also to characterise the TTVs using the N -body code TRADES and the photo-dynamical approach of PyTTV . Results . We find tentative evidence at 3 σ for orbital decay in the TOI-2109 system when we correct the mid-transit timings using the best-fitting sinusoidal model of the TTVs. We do not detect additional transits in the available photometric data, but find evidence supporting the authenticity of the apparent TTVs, indicating a close-by, outer companion with P c > 1.125 d. Due to the fast rotation of the star, the new planetary candidate cannot be detected in the available RV measurements, and its parameters can only be loosely constrained by our joint TTV and RV modelling. Conclusions . TOI-2109 could join a small group of rare HJ systems that host close-by planetary companions, only one of which (WASP-47 b) has an outer companion. More high-precision photometric measurements are necessary to confirm the existence of this planetary companion.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-11-20
DOI
https://doi.org/10.1051/0004-6361/202451068
Citations
9
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
2.98

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article

Hints of a close outer companion to the ultra-hot Jupiter TOI-2109 b

M. Stalport, T. Bárczy, A. Collier Cameron, N. Billot et al.
9 citations
Astronomy and Astrophysics
Astro and Planetary Science
2.98
article

Hints of a close outer companion to the ultra-hot Jupiter TOI-2109 b

M. Stalport, T. Bárczy, A. Collier Cameron, N. Billot, H. Rauer, Y. Alibert, A. M. S. Smith, J. Laskar, W. Benz, R. West, S. Sulis, B. Akinsanmi, M. Gillon, J. Asquier, M.N. Günther, P. F. L. Maxted, V. Nascimbeni, M. Lendl, A. Erikson, Ε. Πάλλη, K. Westerdorff, L. L. Kiss, D. Ségransan, D. Gandolfi, D. Queloz, J. Cabrera, D. Pollacco, A. C. M. Correia, C. Mordasini, A. E. Simon, G. Piotto, B. Edwards, J. Korth, M. B. Davies, Gyula M. Szabó, H. Parviainen, P. Leonardi, R. Alonso, G. Peter, Roberto Ragazzoni, A. Fortier, A. Derekas, B. Ulmer, L. Borsato, I. Ribas, K. W. F. Lam, K. G. Isaak, Ch. Helling, C. Broeg, A. Heitzmann, G. Scandariato, D. Barrado, N. A. Walton, M. Deleuil, M. Güdel, W. Baumjohann, S. C. C. Barros, L. Delrez, E. Villaver, Patricio E. Cubillos, Demetrio Magrin, Valentina Viotto, K. Gazeas, J. Venturini, G. Olofsson, M. Fridlund, L. M. Serrano, Brice-Olivier Demory, N. C. Santos, L. Fossati, D. Ehrenreich, A. Deline, A. Brandeker, T. G. Wilson, S. Udry, B. Merín, Jan‐Vincent Harre, V. Van Grootel, S. G. Sousa, V. Singh, A. Lecavelier des Etangs, Nelson Augusto Rosário, N. Rando, D. Piazza, O. D. S. Demangeon, M.-D. Busch, Sz. Csizmadia, I. Pagano, R. Ottensamer
article en
9 citations

Abstract

Context . Hot Jupiters (HJs) with close-by planetary companions are rare, with only a handful of them having been discovered so far. This could be due to their suggested dynamical histories, which lead to the possible ejection of other planets. TOI-2109 b is special in this regard because it is the HJ with the closest relative separation from its host star, being separated by less than 2.3 stellar radii. Unexpectedly, transit timing measurements from recently obtained CHEOPS observations show low-amplitude transit-timing variations (TTVs). Aims . We aim to search for signs of orbital decay and to characterise the apparent TTVs in an attempt to gain information about a possible companion. Methods . We fitted the newly obtained CHEOPS light curves using TLCM and extracted the resulting mid-transit timings. Successively, we used these measurements in combination with TESS and archival photometric data and radial velocity (RV) data to estimate the rate of tidal orbital decay of TOI-2109 b, and also to characterise the TTVs using the N -body code TRADES and the photo-dynamical approach of PyTTV . Results . We find tentative evidence at 3 σ for orbital decay in the TOI-2109 system when we correct the mid-transit timings using the best-fitting sinusoidal model of the TTVs. We do not detect additional transits in the available photometric data, but find evidence supporting the authenticity of the apparent TTVs, indicating a close-by, outer companion with P c > 1.125 d. Due to the fast rotation of the star, the new planetary candidate cannot be detected in the available RV measurements, and its parameters can only be loosely constrained by our joint TTV and RV modelling. Conclusions . TOI-2109 could join a small group of rare HJ systems that host close-by planetary companions, only one of which (WASP-47 b) has an outer companion. More high-precision photometric measurements are necessary to confirm the existence of this planetary companion.

Astronomy and AstrophysicsVol. 692
Institut d'Astrophysique de Paris (FR), Laboratoire d’Astrophysique de Marseille (FR), Château Gombert (FR), Institut de Mécanique Céleste et de Calcul des Éphémérides (FR)
National Science Foundation, Fondazione CRT, Canadian Celiac Association, UK Space Agency, Centres de Recerca de Catalunya, European Space Agency, University of Warwick, European Commission, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Swedish National Space Agency, Austrian Science Fund, Fonds De La Recherche Scientifique - FNRS, Belgian Federal Science Policy Office, Generalitat de Catalunya, Centre National d’Etudes Spatiales, Ministerio de Ciencia e Innovación, Université de Liège, Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, Instituto de Astrofísica de Canarias, Horizon 2020 Framework Programme, Science and Technology Facilities Council, Fundação para a Ciência e a Tecnologia, Staatssekretariat für Bildung, Forschung und Innovation, European Regional Development Fund, Agencia Estatal de Investigación, National Research, Development and Innovation Office
Openalex Percentile: Top 9%
Astro and Planetary Science
2.98
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