TOI-2084 b and TOI-4184 b : two new sub-Neptunes around M dwarf stars

We present the discovery and validation of two TESS exoplanets orbiting nearby M dwarfs: TOI-2084 b, and TOI-4184b. We characterized the host stars by combining spectra from Shane/Kast and Magellan/FIRE, spectral energy distribution analysis, and stellar evolutionary models. In addition, we used Gemini-South/Zorro & -North/Alopeke high-resolution imaging, archival science images, and statistical validation packages to support the planetary interpretation. We performed a global analysis of multi-colour photometric data from TESS and ground-based facilities in order to derive the stellar and planetary physical parameters for each system. We find that TOI-2084 band TOI-4184 bare sub-Neptune-sized planets with radii of Rp = 2.47 ± 0.13R⊕ and Rp = 2.43 ± 0.21 R⊕, respectively. TOI-2084 b completes an orbit around its host star every 6.08 days, has an equilibrium temperature of Teq = 527 ± 8 K and an irradiation of Sp = 12.8 ± 0.8 S⊕. Its host star is a dwarf of spectral M2.0 ± 0.5 at a distance of 114 pc with an effective temperature of Teff = 3550 ± 50 K, and has a wide, co-moving M8 companion at a projected separation of 1400 au. TOI-4184 b orbits around an M5.0 ± 0.5 type dwarf star (Kmag = 11.87) each 4.9 days, and has an equilibrium temperature of Teq = 412 ± 8 K and an irradiation of Sp = 4.8 ± 0.4 S⊕. TOI-4184 is a metal poor star ([Fe/H] = −0.27 ± 0.09 dex) at a distance of 69 pc with an effective temperature of Teff = 3225 ± 75 K. Both planets are located at the edge of the sub-Jovian desert in the radius-period plane. The combination of the small size and the large infrared brightness of their host stars make these new planets promising targets for future atmospheric exploration with JWST.

Citation

Barkaoui , K , Timmermans , M , Soubkiou , A , Rackham , B V , Burgasser , A J , Chouqar , J , Pozuelos , F J , Collins , K A , Howell , S B , Simcoe , R , Melis , C , Stassun , K G , Tregloan-Reed , J , Cointepas , M , Gillon , M , Bonfils , X , Furlan , E , Gnilka , C L , Almenara , J M , Alonso , R , Benkhaldoun , Z , Bonavita , M , Bouchy , F , Burdanov , A , Chinchilla , P , Davoudi , F , Delrez , L , Demangeon , O , Dominik , M , Demory , B -O , de Wit , J , Dransfield , G , Ducrot , E , Fukui , A , Hinse , T C , Hooton , M J , Jehin , E , Jenkins , J M , Jørgensen , U G , Latham , D W , Garcia , L , Carrazco-Gaxiola , S , Ghachoui , M , Gómez Maqueo Chew , Y , Günther , M N , McCormac , J , Murgas , F , Murray , C A , Narita , N , Niraula , P , Pedersen , P P , Queloz , D , Rebolo-López , R , Ricker , G , Sabin , L , Sajadian , S , Schanche , N , Schwarz , R P , Seager , S , Sebastian , D , Sefako , R , Sohy , S , Southworth , J , Srdoc , G , Thompson , S J , Triaud , A H M J , Vanderspek , R , Wells , R D , Winn , J N & Zúñiga-Fernández , S 2023 , ' TOI-2084 b and TOI-4184 b : two new sub-Neptunes around M dwarf stars ' , Astronomy & Astrophysics , vol. 677 , A38 . https://doi.org/10.1051/0004-6361/202346838

Publication

Astronomy & Astrophysics

Status

Peer reviewed

DOI

https://doi.org/10.1051/0004-6361/202346838

ISSN

0004-6361

Type

Journal article

Rights

Copyright © The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.

Description

Funding: The research leading to these results has received funding from the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. This research is in part funded by the European Union’s Horizon 2020 research and innovation program (grants agreements n◦ 803193/BEBOP), and from the Science and Technology Facilities Council (STFC; grant n◦ ST/S00193X/1). U.G.J. gratefully acknowledges support from tthe European Union H2020-MSCA-ITN-2019 under grant No. 860470 (CHAMELEON). The authors acknowledge funding from the European Research Council under the ERC Grant Agreement n. 337591-ExTrA.