TOI–757 b: an eccentric transiting mini–Neptune on a 17.5–d orbit

ABSTRACT We report the spectroscopic confirmation and fundamental properties of TOI$-$757 b, a mini$-$Neptune on a 17.5$-$d orbit transiting a bright star ($V\, =\, 9.7$ mag) discovered by the TESS mission. We acquired high$-$precision radial velocity measurements with the HARPS, ESPRESSO, and PFS spectrographs to confirm the planet detection and determine its mass. We also acquired space$-$borne transit photometry with the CHEOPS space telescope to place stronger constraints on the planet radius, supported with ground$-$based LCOGT photometry. WASP and KELT photometry were used to help constrain the stellar rotation period. We also determined the fundamental parameters of the host star. We find that TOI$-$757 b has a radius of $R_{\mathrm{p}} = 2.5 \pm 0.1 R_{\oplus }$ and a mass of $M_{\mathrm{p}} = 10.5^{+2.2}_{-2.1} M_{\oplus }$, implying a bulk density of $\rho _{\text{p}} = 3.6 \pm 0.8$ g cm$^{-3}$. Our internal composition modelling was unable to constrain the composition of TOI$-$757 b, highlighting the importance of atmospheric observations for the system. We also find the planet to be highly eccentric with e = 0.39$^{+0.08}_{-0.07}$, making it one of the very few highly eccentric planets among precisely characterized mini$-$Neptunes. Based on comparisons to other similar eccentric systems, we find a likely scenario for TOI$-$757 b’s formation to be high eccentricity migration due to a distant outer companion. We additionally propose the possibility of a more intrinsic explanation for the high eccentricity due to star$-$star interactions during the earlier epoch of the Galactic disc formation, given the low metallicity and older age of TOI$-$757.

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UNC Libraries
Published
2024-11-06
DOI
https://doi.org/10.17615/gser-4n45
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Astro and Planetary Science
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article
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article

TOI–757 b: an eccentric transiting mini–Neptune on a 17.5–d orbit

M. Stalport, T. Bárczy, A. Bonfanti, Tansu Daylan et al.
UNC Libraries
Astro and Planetary Science
article

TOI–757 b: an eccentric transiting mini–Neptune on a 17.5–d orbit

M. Stalport, T. Bárczy, A. Bonfanti, Tansu Daylan, Simon Albrecht, A. Collier Cameron, N. Billot, H. Rauer, Y. Alibert, A. M. S. Smith, J. Laskar, Jon M. Jenkins, W. Benz, Maximilian N. Günther, Andrew W. Mann, R. Luque, F Bouchy, L. Borsato, Ramotholo Sefako, M. Gillon, J. Asquier, P. F. L. Maxted, V. Nascimbeni, H. P. Osborn, M. Lendl, Ε. Πάλλη, L. L. Kiss, Joseph D. Twicken, D. Ségransan, D. Gandolfi, D. Queloz, Michael B. Lund, J. Cabrera, A. F. Lanza, D. Pollacco, A. C. M. Correia, C. Mordasini, A. E. Simon, G. Piotto, Malena Rice, M. B. Davies, Sébastien Salmon, Samuel W. Yee, R. Paul Butler, Karen A. Collins, J. A. Egger, G. Peter, Steve B. Howell, Zahra Essack, Shubham Kanodia, Roberto Ragazzoni, H. L. M. Osborne, J. Korth, Nolan Grieves, Stephen A. Shectman, Sara Seager, A. Fortier, A. Derekas, Seth Redfield, Jeffrey D. Crane, Johanna Teske, A. P. Hatzes, I. Ribas, K. W. F. Lam, Ryan J. Oelkers, K. G. Isaak, Teruyuki Hirano, J. H. Livingston, S Udry, Ch. Helling, G. Ricker, Vincent Van Eylen, C. Broeg, D. J. Osip, A. Heitzmann, Kevin I. Collins, G. Scandariato, J Hasiba, M Fridlund, A. Alqasim, Avi Shporer, Edward M. Bryant, D. Barrado, N. A. Walton, A. Lecavelier des Étangs, Ingo Walter, Elisa Goffo, W. Baumjohann, S. C. C. Barros, S. Hoyer, C. Hellier, L. Delrez, E. Villaver, N. C. Santos, Patricio E. Cubillos, Demetrio Magrin, Sharon X. Wang, Valentina Viotto, Norio Narita, K. Gazeas, J. Venturini, G. Olofsson, R Alonso, L. M. Serrano, Brice-Olivier Demory, M Deleuil, L. Fossati, D. Ehrenreich, R. Vanderspek, A. Deline, William D. Cochran, B Edwards, A. Brandeker, T. G. Wilson, G. Nowak, V. Van Grootel, S. G. Sousa, Nelson Augusto Rosário, N. Rando, O. D. S. Demangeon, Gy. M. Szabó, I. Thompson, J. Villaseñor, Anders Erikson, Sz. Csizmadia, T. Beck, M. Güdel, M. Rieder, Joshua N. Winn, Gregor Srdoč, I. Pagano, R. Ottensamer
article en

Abstract

ABSTRACT We report the spectroscopic confirmation and fundamental properties of TOI$-$757 b, a mini$-$Neptune on a 17.5$-$d orbit transiting a bright star ($V\, =\, 9.7$ mag) discovered by the TESS mission. We acquired high$-$precision radial velocity measurements with the HARPS, ESPRESSO, and PFS spectrographs to confirm the planet detection and determine its mass. We also acquired space$-$borne transit photometry with the CHEOPS space telescope to place stronger constraints on the planet radius, supported with ground$-$based LCOGT photometry. WASP and KELT photometry were used to help constrain the stellar rotation period. We also determined the fundamental parameters of the host star. We find that TOI$-$757 b has a radius of $R_{\mathrm{p}} = 2.5 \pm 0.1 R_{\oplus }$ and a mass of $M_{\mathrm{p}} = 10.5^{+2.2}_{-2.1} M_{\oplus }$, implying a bulk density of $\rho _{\text{p}} = 3.6 \pm 0.8$ g cm$^{-3}$. Our internal composition modelling was unable to constrain the composition of TOI$-$757 b, highlighting the importance of atmospheric observations for the system. We also find the planet to be highly eccentric with e = 0.39$^{+0.08}_{-0.07}$, making it one of the very few highly eccentric planets among precisely characterized mini$-$Neptunes. Based on comparisons to other similar eccentric systems, we find a likely scenario for TOI$-$757 b’s formation to be high eccentricity migration due to a distant outer companion. We additionally propose the possibility of a more intrinsic explanation for the high eccentricity due to star$-$star interactions during the earlier epoch of the Galactic disc formation, given the low metallicity and older age of TOI$-$757.

UNC Libraries
University of North Carolina at Chapel Hill (US)
National Science Foundation, National Aeronautics and Space Administration, Simons Foundation, California Institute of Technology, Fondazione CRT, UK Space Agency, Space Telescope Science Institute, Centres de Recerca de Catalunya, Universidad de La Laguna, 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, Ministry of Science, ICT and Future Planning, Korea Astronomy and Space Science Institute, Université de Genève, Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, UAE Space Agency, Ames Research Center, Horizon 2020 Framework Programme, Science Mission Directorate, 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
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