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

A Alqasim*, N Grieves, N M Rosário, D Gandolfi*, J H Livingston, S Sousa, K A Collins, J K Teske, M Fridlund, J A Egger, J Cabrera, C Hellier, A F Lanza, V Van Eylen, F Bouchy, R J Oelkers, G Srdoc, S Shectman, M Günther, E GoffoT Wilson, L M Serrano, A Brandeker, S X Wang, A Heitzmann, A Bonfanti, L Fossati, Y Alibert, L Delrez, R Sefako, S Barros, K I Collins, O D S Demangeon, S H Albrecht, R Alonso, J Asquier, T Barczy, D Barrado, W Baumjohann, T Beck, W Benz, N Billot, L Borsato, C Broeg, E M Bryant, R P Butler, W D Cochran, A Collier Cameron, A C M Correia, J D Crane, Sz Csizmadia, P E Cubillos, M B Davies, T Daylan, M Deleuil, A Deline, B -O Demory, A Derekas, B Edwards, D Ehrenreich, A Erikson, Z Essack, A Fortier, K Gazeas, M Gillon, M Gudel, J Hasiba, A P Hatzes, Ch Helling, T Hirano, S B Howell, S Hoyer, K G Isaak, J M Jenkins, S Kanodia, L L Kiss, J Korth, K W F Lam, J Laskar, A Lecavelier des Etangs, M Lendl, M B Lund, R Luque, A W Mann, D Magrin, P F L Maxted, C Mordasini, N Narita, V Nascimbeni, G Nowak, G Olofsson, H P Osborn, H L M Osborne, D Osip, R Ottensamer, I Pagano, E Palle, G Peter, G Piotto, D Pollacco, D Queloz, R Ragazzoni, N Rando, H Rauer, S Redfield, I Ribas, M Rice, G R Ricker, M Rieder, S Salmon, N C Santos, G Scandariato, S Seager, D Segransan, A Shporer, A E Simon, A M S Smith, M Stalport, Gy M Szabo, I Thompson, J D Twicken, S Udry, R Vanderspek, V Van Grootel, J Venturini, E Villaver, J Villaseñor, V Viotto, I Walter, N A Walton, J N Winn, S W Yee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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 Rp = 2.5 ± 0.1 R⊕ and a mass of Mp = 10.5+2.2-2.1 M⊕, implying a bulk density of ρp = 3.6 ± 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.
Original languageEnglish
Article numberstae1767
Pages (from-to)1-26
Number of pages26
JournalMonthly Notices of the Royal Astronomical Society
Volume533
Issue number1
Early online date31 Jul 2024
DOIs
Publication statusPublished - Sept 2024

Keywords

  • Techniques: photometric
  • Techniques: radial velocities
  • Planets and satellites: composition
  • Planets and satellites: interiors
  • Stars: individual: TOI-757 (TIC 130924120)

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