학술논문
The Discovery and Follow-up of Four Transiting Short-period Sub-Neptunes Orbiting M dwarfs
Document Type
Working Paper
Author
Hori, Y.; Fukui, A.; Hirano, T.; Narita, N.; de Leon, J. P.; Ishikawa, H. T.; Hartman, J. D.; Morello, G.; García, N. Abreu; Hernández, L. Álvarez; Béjar, V. J. S.; Calatayud-Borras, Y.; Carleo, I.; Enoc, G.; Esparza-Borges, E.; Fukuda, I.; Galán, D.; Geraldía-González, S.; Hayashi, Y.; Ikoma, M.; Ikuta, K.; Isogai, K.; Kagetani, T.; Kawai, Y.; Kawauchi, K.; Kimura, T.; Kodama, T.; Korth, J.; Kusakabe, N.; Laza-Ramos, A.; Livingston, J. H.; Luque, R.; Miyakawa, K.; Mori, M.; Torres, S. Muñoz; Murgas, F.; Orell-Miquel, J.; Palle, E.; Parviainen, H.; Peláez-Torres, A.; Puig-Subirá, M.; Sánchez-Benavente, M.; Sosa-Guillén, P.; Stangret, M.; Terada, Y.; Watanabe, N.; Bakos, G. Á.; Barkaoui, K.; Beichman, C.; Benkhaldoun, Z.; Boyle, A. W.; Ciardi, D. R.; Clark, C. A.; Collins, K. A.; Collins, K. I.; Conti, D. M.; Crossfield, I. J. M.; Everett, M. E.; Furlan, E.; Ghachoui, M.; Gillon, M.; Gonzales, E. J.; Higuera, J.; Horne, K.; Howell, S. B.; Jehin, E.; Lester, K. V.; Lund, M. B.; Matson, R.; Matthews, E. C.; Pozuelos, F. J.; Safonov, B. S.; Schlieder, J. E.; Schwarz, R. P.; Sefako, R.; Srdoc, G.; Strakhov, I. A.; Waalkes, W. C.; Ziegler, C.; Charbonneau, D.; Essack, Z.; Timmermans, M.; Guerrero, N. M.; Harakawa, H.; Hedges, C.; Ishizuka, M.; Jenkins, J. M.; Konishi, M.; Kotani, T.; Kudo, T.; Kurokawa, T.; Kuzuhara, M.; Nishikawa, J.; Omiya, M.; Ricker, G. R.; Seager, S.; Serizawa, T.; Striegel, S.; Tamura, M.; Ueda, A.; Vanderspek, R.; Vievard, S.; Winn, J. N.
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Subject
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Abstract
Sub-Neptunes with $2-3R_\oplus$ 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 $R_\mathrm{p} = 2.740^{+0.082}_{-0.079}\,R_\oplus$, $2.769^{+0.073}_{-0.068}\,R_\oplus$, $2.120\pm0.067\,R_\oplus$, and $2.830^{+0.068}_{-0.066}\,R_\oplus$ and orbital periods of $P = 8.02$, $8.11$, $5.80$, and $3.08$\,days, respectively. Doppler monitoring with Subaru/InfraRed Doppler instrument led to 2$\sigma$ upper limits on the masses of $<19.1\ M_\oplus$, $<19.5\ M_\oplus$, $<6.8\ M_\oplus$, and $<15.6\ M_\oplus$ 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 $e \sim 0.2-0.3$. The fact that tidal circularization of their orbits is not achieved over 1 Gyr suggests inefficient tidal dissipation in their interiors.
Comment: Accepted for publication in AJ, 32 pages, 17 figures, 6 tables
Comment: Accepted for publication in AJ, 32 pages, 17 figures, 6 tables