DOE OSTI · 2427420
TOI–757 b: an eccentric transiting mini–Neptune on a 17.5–d orbit
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.
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Alqasim, A. (ORCID:0000000151025505), Grieves, N. (ORCID:0000000181050373), Rosário, N. M. (ORCID:0000000285886730), Gandolfi, D. (ORCID:0000000186279628), Livingston, J. H. (ORCID:0000000248813620), Sousa, S. (ORCID:0000000190472965), Collins, K. A. (ORCID:0000000165889574), Teske, J. K. (ORCID:0009000828015040), Fridlund, M. (ORCID:0000000208558426), Egger, J. A. (ORCID:0000000316284231), Cabrera, J. (ORCID:0000000166535487), Hellier, C. (ORCID:0000000234391439), Lanza, A. F. (ORCID:0000000159287251), Van Eylen, V. (ORCID:0000000155428870), Bouchy, F. (ORCID:000000027613393X), Oelkers, R. J., Srdoc, G., Shectman, S. (ORCID:0000000286816136), Günther, M. (ORCID:0000000231649086), Goffo, E. (ORCID:000000019670961X), Wilson, T. (ORCID:0000000187491962), Serrano, L. M., Brandeker, A., Wang, S. X., Heitzmann, A., Bonfanti, A., Fossati, L., Alibert, Y. (ORCID:0000000246448818), Delrez, L. (ORCID:0000000161084808), Sefako, R. (ORCID:0000000339046754), Barros, S. (ORCID:0000000324343625), Collins, K. I. (ORCID:0000000327813207), Demangeon, O. D. S. (ORCID:0000000179180355), Albrecht, S. H. (ORCID:0000000317628235), Alonso, R. (ORCID:0000000184628126), Asquier, J., Barczy, T. (ORCID:0000000278224413), Barrado, D. (ORCID:0000000259719242), Baumjohann, W. (ORCID:0000000162710110), Beck, T., Benz, W. (ORCID:0000000178966479), Billot, N. (ORCID:0000000334293836), Borsato, L. (ORCID:0000000300669268), Broeg, C. (ORCID:0000000151322614), Bryant, E. M. (ORCID:0000000179044441), Butler, R. P. (ORCID:0000000313053761), Cochran, W. D. (ORCID:0000000196623496), Cameron, A. Collier (ORCID:0000000288637828), Correia, A. C. M., Crane, J. D. (ORCID:000000025226787X), Csizmadia, Sz (ORCID:0000000168039698), Cubillos, P. E., Davies, M. B. (ORCID:0000000160801190), Daylan, T. (ORCID:0000000269399211), Deleuil, M. (ORCID:0000000160360225), Deline, A., Demory, B. -O (ORCID:0000000293555165), Derekas, A., Edwards, B., Ehrenreich, D. (ORCID:0000000197045405), Erikson, A., Essack, Z. (ORCID:0000000224820180), Fortier, A. (ORCID:0000000184503374), Gazeas, K. (ORCID:0000000288553923), Gillon, M. (ORCID:0000000314627739), Gudel, M., Hasiba, J., Hatzes, A. P., Helling, Ch, Hirano, T., Howell, S. B. (ORCID:0000000225322853), Hoyer, S. (ORCID:0000000334772466), Isaak, K. G. (ORCID:0000000185851717), Jenkins, J. M. (ORCID:0000000247159460), Kanodia, S. (ORCID:0000000184014300), Kiss, L. L., Korth, J. (ORCID:0000000200766239), Lam, K. W. F. (ORCID:0000000299106088), Laskar, J. (ORCID:000000032634789X), Etangs, A. Lecavelier des (ORCID:0000000256375253), Lendl, M. (ORCID:0000000196991459), Lund, M. B. (ORCID:0000000325271598), Luque, R. (ORCID:0000000246712957), Mann, A. W. (ORCID:0000000336541602), Magrin, D. (ORCID:000000030312313X), Maxted, P. F. L. (ORCID:0000000337941317), Mordasini, C., Narita, N. (ORCID:0000000185112981), Nascimbeni, V. (ORCID:0000000197701214), Nowak, G., Olofsson, G. (ORCID:0000000337477120), Osborn, H. P. (ORCID:0000000240474724), Osborne, H. L. M., Osip, D. (ORCID:0000000304129664), Ottensamer, R. (ORCID:0000000156845836), Pagano, I. (ORCID:0000000195734928), Palle, E. (ORCID:0000000309871593), Peter, G. (ORCID:0000000161012513), Piotto, G. (ORCID:0000000299376387), Pollacco, D.. 2024-07-31. TOI–757 b: an eccentric transiting mini–Neptune on a 17.5–d orbit. https://doi.org/10.1093/mnras%2Fstae1767
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