The Discovery and Follow-up of Four Transiting Short-period Sub-Neptunes Orbiting M Dwarfs

DOI: 
10.3847/1538-3881/ad4115
Publication date: 
11/06/2024
Main author: 
Hori, Yasunori
IAA authors: 
Morello, Giuseppe;Pozuelos, Francisco J.
Authors: 
Hori, Yasunori;Fukui, Akihiko;Hirano, Teruyuki;Narita, Norio;de Leon, Jerome P.;Ishikawa, Hiroyuki Tako;Hartman, Joel D.;Morello, Giuseppe;García, Nestor Abreu;Álvarez Hernández, Leticia;Béjar, Víctor J. S.;Calatayud-Borras, Yéssica;Carleo, Ilaria;Enoc, Gareb;Esparza-Borges, Emma;Fukuda, Izuru;Galán, Daniel;Geraldía-González, Samuel;Hayashi, Yuya;Ikoma, Masahiro;Ikuta, Kai;Isogai, Keisuke;Kagetani, Taiki;Kawai, Yugo;Kawauchi, Kiyoe;Kimura, Tadahiro;Kodama, Takanori;Korth, Judith;Kusakabe, Nobuhiko;Laza-Ramos, Andrés;Livingston, John H.;Luque, Rafael;Miyakawa, Kohei;Mori, Mayuko;Murgas, Felipe;Orell-Miquel, Jaume;Palle, Enric;Parviainen, Hannu;Peláez-Torres, Alberto;Puig-Subirà, Marta;Sánchez-Benavente, Manuel;Sosa-Guillén, Paula;Stangret, Monika;Terada, Yuka;Muñoz Torres, Sara;Watanabe, Noriharu;Bakos, Gaspar Á.;Barkaoui, Khalid;Beichman, Charles;Benkhaldoun, Zouhair;Boyle, Andrew W.;Ciardi, David R.;Clark, Catherine A.;Collins, Karen A.;Collins, Kevin I.;Conti, Dennis M.;Crossfield, Ian J. M.;Everett, Mark E.;Furlan, Elise;Ghachoui, Mourad;Gillon, Michaël;Gonzales, Erica J.;Higuera, Jesus;Horne, Keith;Howell, Steve B.;Jehin, Emmanuël;Lester, Kathryn V.;Lund, Michael B.;Matson, Rachel;Matthews, Elisabeth C.;Pozuelos, Francisco J.;Safonov, Boris S.;Schlieder, Joshua E.;Schwarz, Richard P.;Sefako, Ramotholo;Srdoc, Gregor;Strakhov, Ivan A.;Timmermans, Mathilde;Waalkes, William C.;Ziegler, Carl;Charbonneau, David;Essack, Zahra;Guerrero, Natalia M.;Harakawa, Hiroki;Hedges, Christina;Ishizuka, Masato;Jenkins, Jon M.;Konishi, Mihoko;Kotani, Takayuki;Kudo, Tomoyuki;Kurokawa, Takashi;Kuzuhara, Masayuki;Nishikawa, Jun;Omiya, Masashi;Ricker, George R.;Seager, Sara;Serizawa, Takuma;Striegel, Stephanie;Tamura, Motohide;Ueda, Akitoshi;Vanderspek, Roland;Vievard, Sébastien;Winn, Joshua N.
Journal: 
The Astronomical Journal
Publication type: 
Article
Volume: 
167
Pages: 
289
Abstract: 
Sub-Neptunes with radii of 2–3 R <SUB>⊕</SUB> are intermediate in size between rocky planets and Neptune-sized planets. The orbital properties and bulk compositions of transiting sub-Neptunes provide clues to the formation and evolution of close-in small planets. In this paper, we present the discovery and follow-up of four sub-Neptunes orbiting M dwarfs (TOI-782, TOI-1448, TOI-2120, and TOI-2406), three of which were newly validated by ground-based follow-up observations and statistical analyses. TOI-782 b, TOI-1448 b, TOI-2120 b, and TOI-2406 b have radii of , , 2.120 ± 0.067 R <SUB>⊕</SUB>, and and orbital periods of P = 8.02, 8.11, 5.80, and 3.08 days, respectively. Doppler monitoring with the Subaru/InfraRed Doppler instrument led to 2σ upper limits on the masses of &lt;19.1 M <SUB>⊕</SUB>, &lt;19.5 M <SUB>⊕</SUB>, &lt;6.8 M <SUB>⊕</SUB>, and &lt;15.6 M <SUB>⊕</SUB> for TOI-782 b, TOI-1448 b, TOI-2120 b, and TOI-2406 b, respectively. The mass–radius relationship of these four sub-Neptunes testifies to the existence of volatile material in their interiors. These four sub-Neptunes, which are located above the so-called "radius valley," are likely to retain a significant atmosphere and/or an icy mantle on the core, such as a water world. We find that at least three of the four sub-Neptunes (TOI-782 b, TOI-2120 b, and TOI-2406 b), orbiting M dwarfs older than 1 Gyr, are likely to have eccentricities of e ∼ 0.2–0.3. The fact that tidal circularization of their orbits is not achieved over 1 Gyr suggests inefficient tidal dissipation in their interiors.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2024AJ....167..289H/abstract
ADS Bibcode: 
2024AJ....167..289H
Keywords: 
Exoplanets;Mini Neptunes;Radial velocity;Transit photometry;Tides;M dwarf stars;498;1063;1332;1709;1702;982;Astrophysics - Earth and Planetary Astrophysics