TOI-1634 b: An Ultra-short-period Keystone Planet Sitting inside the M-dwarf Radius Valley

Cloutier, Ryan and Charbonneau, David and Stassun, Keivan G. and Murgas, Felipe and Mortier, Annelies and Massey, Robert and Lissauer, Jack J. and Latham, David W. and Irwin, Jonathan and Haywood, Raphaelle D. and Guerra, Pere and Girardin, Eric and Giacalone, Steven A. and Bosch-Cabot, Pau and Bieryla, Allyson and Winn, Joshua and Watson, Christopher A. and Vanderspek, Roland and Udry, Stephane and Tamura, Motohide and Sozzetti, Alessandro and Shporer, Avi and Segransan, Damien and Seager, Sara and Savel, Arjun B. and Sasselov, Dimitar and Rose, Mark and Ricker, George and Rice, Ken and Quintana, Elisa V. and Quinn, Samuel N. and Piotto, Giampaolo and Phillips, David and Pepe, Francesco and Pedani, Marco and Parviainen, Hannu and Palle, Enric and Narita, Norio and Molinari, Emilio and Micela, Giuseppina and McDermott, Scott and Mayor, Michel and Matson, Rachel A. and Martinez Fiorenzano, Aldo F. and Lovis, Christophe and Lopez-Morales, Mercedes and Kusakabe, Nobuhiko and Jensen, Eric L. N. and Jenkins, Jon M. and Huang, Chelsea X. ORCID: and Howell, Steve B. and Harutyunyan, Avet and Furesz, Gabor and Fukui, Akihiko and Esquerdo, Gilbert A. and Esparza-Borges, Emma and Dumusque, Xavier and Dressing, Courtney D. and Di Fabrizio, Luca and Collins, Karen A. and Cameron, Andrew Collier and Christiansen, Jessie L. and Cecconi, Massimo and Buchhave, Lars A. and Boschin, Walter and Andreuzzi, Gloria (2021) TOI-1634 b: An Ultra-short-period Keystone Planet Sitting inside the M-dwarf Radius Valley. The Astronomical Journal, 162 (2):79. pp. 1-21. ISSN 0004-6256

Text (Published Version)

Download (2MB) | Preview


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}_{-0.081}^{+0.080} R⊕) orbiting a nearby M2 dwarf (K s = 8.7, R s = 0.450 R o˙, M s = 0.502 M o˙) 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}_{-0.70}^{+0.68} M⊕, 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 composition 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 Earth supports the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with M-s less than or similar to 0.5 M-circle dot.

Statistics for USQ ePrint 47431
Statistics for this ePrint Item
Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 03 Apr 2022 23:25
Last Modified: 09 Jun 2022 03:38
Uncontrolled Keywords: Planetary system formation (1257); Exoplanet structure (495); Radial velocity (1332); Transit photometry (1709); Low mass stars (2050); Astrophysics - Earth and Planetary Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Identification Number or DOI:

Actions (login required)

View Item Archive Repository Staff Only