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

Alqasim, A.; Grieves, N.; Rosário, N. M.; Gandolfi, D.; Livingston, J. H.; Sousa, S.; Collins, K. A.; Teske, J. K.; Fridlund, M.; Egger, J. A.; Cabrera, J.; Hellier, C.; Lanza, A. F.; Van Eylen, V.; Bouchy, F.; Oelkers, R. J.; Srdoc, G.; Shectman, S.; Günther, M.; Goffo, E.; Wilson, T.; Serrano, L. M.; Brandeker, A.; Wang, S. X.; Heitzmann, A.; Bonfanti, A.; Fossati, L.; Alibert, Y.; Delrez, L.; Sefako, R.; Barros, S.; Collins, K. I.; Demangeon, O. D. S.; Albrecht, S. H.; Alonso, R.; Asquier, J.; Barczy, T.; Barrado, D.; Baumjohann, W.; Beck, T.; Benz, W.; Billot, N.; Borsato, L.; Broeg, C.; Bryant, E. M.; Butler, R. P.; Cochran, W. D.; Cameron, A. Collier; Correia, A. C. M.; Crane, J. D.; Csizmadia, Sz; Cubillos, P. E.; Davies, M. B.; Daylan, T.; Deleuil, M.; Deline, A.; Demory, B. -O.; Derekas, A.; Edwards, B.; Ehrenreich, D.; Erikson, A.; Essack, Z.; Fortier, A.; Gazeas, K.; Gillon, M.; Gudel, M.; Hasiba, J.; Hatzes, A. P.; Helling, Ch; Hirano, T.; Howell, S. B.; Hoyer, S.; Isaak, K. G.; Jenkins, J. M.; Kanodia, S.; Kiss, L. L.; Korth, J.; Lam, K. W. F.; Laskar, J.; Etangs, A. Lecavelier des; Lendl, M.; Lund, M. B.; Luque, R.; Mann, A. W.; Magrin, D.; Maxted, P. F. L.; Mordasini, C.; Narita, N.; Nascimbeni, V.; Nowak, G.; Olofsson, G.; Osborn, H. P.; Osborne, H. L. M.; Osip, D.; Ottensamer, R.; Pagano, I.; Palle, E.; Peter, G.; Piotto, G.; Pollacco, D. et al.
Referencia bibliográfica

Monthly Notices of the Royal Astronomical Society

Fecha de publicación:
9
2024
Número de autores
132
Número de autores del IAC
4
Número de citas
0
Número de citas referidas
0
Descripción
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.