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

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abstract

  • 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 ⊕ , r p = 1.790 − 0.081 + 0.080 R ⊕) orbiting a nearby M2 dwarf (K s  = 8.7, R s  = 0.450 R ⊙, M s  = 0.502 M ⊙) 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 σ 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 ≲ 0.5 M ⊙.

authors

  • Cloutier, Ryan
  • Charbonneau, David
  • Stassun, Keivan G
  • Murgas, Felipe
  • Mortier, Annelies
  • Massey, Robert
  • Lissauer, Jack J
  • Latham, David W
  • Irwin, Jonathan
  • Haywood, Raphaëlle D
  • Guerra, Pere
  • Girardin, Eric
  • Giacalone, Steven A
  • Bosch-Cabot, Pau
  • Bieryla, Allyson
  • Winn, Joshua
  • Watson, Christopher A
  • Vanderspek, Roland
  • Udry, Stéphane
  • Tamura, Motohide
  • Sozzetti, Alessandro
  • Shporer, Avi
  • Ségransan, Damien
  • Seager, Sara
  • Savel, Arjun B
  • Sasselov, Dimitar
  • Rose, Mark
  • Ricker, George
  • Rice, Ken
  • Quintana, Elisa V
  • Quinn, Samuel N
  • Piotto, Giampaolo
  • Phillips, David
  • Pepe, Francesco
  • Pedani, Marco
  • Parviainen, Hannu
  • Palle, Enric
  • Narita, Norio
  • Molinari, Emilio
  • Micela, Giuseppina
  • McDermott, Scott
  • Mayor, Michel
  • Matson, Rachel A
  • Martinez Fiorenzano, Aldo F
  • Lovis, Christophe
  • López-Morales, Mercedes
  • Kusakabe, Nobuhiko
  • Jensen, Eric LN
  • Jenkins, Jon M
  • Huang, Chelsea X
  • Howell, Steve B
  • Harutyunyan, Avet
  • Fűrész, Gábor
  • Fukui, Akihiko
  • Esquerdo, Gilbert A
  • Esparza-Borges, Emma
  • Dumusque, Xavier
  • Dressing, Courtney D
  • Fabrizio, Luca Di
  • Collins, Karen A
  • Cameron, Andrew Collier
  • Christiansen, Jessie L
  • Cecconi, Massimo
  • Buchhave, Lars A
  • Boschin, Walter
  • Andreuzzi, Gloria

publication date

  • August 1, 2021