학술논문
TOI-1634 b: an Ultra-Short Period Keystone Planet Sitting Inside the M Dwarf Radius Valley
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Working Paper
Author
Cloutier, R.; Charbonneau, D.; Stassun, K. G.; Murgas, F.; Mortier, A.; Massey, R.; Lissauer, J. J.; Latham, D. W.; Irwin, J.; Haywood, R. D.; Guerra, P.; Girardin, E.; Giacalone, S. A.; Bosch-Cabot, P.; Bieryla, A.; Winn, J.; Watson, C. A.; Vanderspek, R.; Udry, S.; Tamura, M.; Sozzetti, A.; Shporer, A.; Ségransan, D.; Seager, S.; Savel, A. B.; Sasselov, D.; Rose, M.; Ricker, G.; Rice, K.; Quintana, E. V.; Quinn, S. N.; Piotto, G.; Phillips, D.; Pepe, F.; Pedani, M.; Parviainen, H.; Palle, E.; Narita, N.; Molinari, E.; Micela, G.; McDermott, S.; Mayor, M.; Matson, R. A.; Fiorenzano, A. F. Martinez; Lovis, C.; López-Morales, M.; Kusakabe, N.; Jensen, E. L. N.; Jenkins, J. M.; Huang, C. X.; Howell, S. B.; Harutyunyan, A.; Fűrész, G.; Fukui, A.; Esquerdo, G. A.; Esparza-Borges, E.; Dumusque, X.; Dressing, C. D.; Di Fabrizio, L.; Collins, K. A.; Cameron, A. Collier; Christiansen, J. L.; Cecconi, M.; Buchhave, L. A.; Boschin, W.; Andreuzzi, G.
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Abstract
Studies of close-in planets orbiting M dwarfs have suggested that the M dwarf radius valley may be well-explained by distinct formation timescales between enveloped terrestrials, and rocky planets that form at late times in a gas-depleted environment. This scenario is at odds with the picture that close-in rocky planets form with a primordial gaseous envelope that is subsequently stripped away by some thermally-driven mass loss process. These two physical scenarios make unique predictions of the rocky/enveloped transition's dependence on orbital separation such that studying the compositions of planets within the M dwarf radius valley may be able to establish the dominant physics. Here, we present the discovery of one such keystone planet: the ultra-short period planet TOI-1634 b ($P=0.989$ days, $F=121 F_{\oplus}$, $r_p = 1.790^{+0.080}_{-0.081} R_{\oplus}$) orbiting a nearby M2 dwarf ($K_s=8.7$, $R_s=0.45 R_{\odot}$, $M_s=0.50 M_{\odot}$) and whose size and orbital period sit within the M dwarf radius valley. We confirm the TESS-discovered planet candidate using extensive ground-based follow-up campaigns, including a set of 32 precise radial velocity measurements from HARPS-N. We measure a planetary mass of $4.91^{+0.68}_{-0.70} M_{\oplus}$, which makes TOI-1634 b inconsistent with an Earth-like composition at $5.9\sigma$ and thus requires either an extended gaseous envelope, a large volatile-rich layer, or a rocky portion that is not dominated by iron and silicates to explain its mass and radius. The discovery that the bulk composition of TOI-1634 b is inconsistent with that of the Earth favors the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with $M_s\lesssim 0.5 M_{\odot}$.
Comment: 27 pages, 13 figures, accepted to AAS journals. Our time series are included as a csv file in the arXiv source files
Comment: 27 pages, 13 figures, accepted to AAS journals. Our time series are included as a csv file in the arXiv source files