TY - JOUR
T1 - The TOI-1117 multiplanetary system
T2 - 3 sub-Neptunes, 1 in both the Neptunian Desert and Radius Valley
AU - Lockley, Isobel S.
AU - Armstrong, David J.
AU - Fernández, Jorge Fernández
AU - Millholland, Sarah
AU - Knierim, Henrik
AU - Mena, Elisa Delgado
AU - Sousa, Sergio
AU - Collins, Karen A.
AU - Watkins, Cristilyn N.
AU - Howell, Steve B.
AU - Adibekyan, Vardan
AU - Helled, Ravit
AU - Ziegler, Carl
AU - Bayliss, Daniel
AU - Briceño, César
AU - Castro-González, Amadeo
AU - Clark, Catherine A.
AU - Collins, Kevin I.
AU - Christiansen, Jessie L.
AU - Cui, Kaiming
AU - Diaz, Rodrigo
AU - Jenkins, Jon M.
AU - Fetzner Keniger, Marcelo A.
AU - Kunimoto, Michelle
AU - Law, Nicholas
AU - Lillo-Box, Jorge
AU - Littlefield, Colin
AU - Mann, Andrew W.
AU - Mitchell, Morgan A.
AU - Nielsen, Louise D.
AU - Rodrigues, José
AU - Rowden, Pam
AU - Santos, Nuno C.
AU - Seager, Sara
AU - Wheatley, Peter J.
AU - Winn, Joshua
N1 - Publisher Copyright:
© 2025 The Author(s).
PY - 2025/8/1
Y1 - 2025/8/1
N2 - We present the discovery of three sub-Neptune planets around TOI-1117, a Sun-like star with mass 0.97 ± 0.02 M☉, radius 1.05 ± 0.03 R☉, age 4.42 ± 1.50 Gyr, and effective temperature 5635 ± 62 K. Light curves from Transiting Exoplanet Survey Satellite and Las Cumbres Observatory Global Telescope show a transiting sub-Neptune with a 2.23-d period, mass Mb = 8.90+−00.9695 M and radius Rb = 2.46+−00.1213 R. This is a rare ‘hot Neptune’ that falls within the parameter spaces known as the ‘Neptunian Desert’ and the ‘Radius Valley’. Two more planetary signals are detected in HARPS (High Accuracy Radial velocity Planetary Searcher) radial velocities, revealing two non-transiting planets with minimum masses Mc = 7.46+−11.6243 M and Md = 9.06+−12.7807 M, and periods of 4.579 ± 0.004 and 8.67 ± 0.01 d. The eccentricities were poorly constrained by the HARPS data, with upper limits eb = 0.11, ec = 0.29, and ed = 0.24. However, dynamical simulations of the TOI-1117 system, suggest that the orbits must be nearly circular to be stable. The simulations also show that TOI-1117 b and c are likely to be in a near 2:1 resonance. The multiplanet nature of TOI-1117 makes it a more complex case for formation theories of the Neptunian Desert and Radius Valley, as current theories such as high-eccentricity migration are too turbulent to produce a stable, non-eccentric, and multiplanet system. Moreover, analysis of TOI-1117 b’s photoevaporation history found rocky core and H/He atmosphere models to be inconsistent with observations, whilst water-rich scenarios were favoured.
AB - We present the discovery of three sub-Neptune planets around TOI-1117, a Sun-like star with mass 0.97 ± 0.02 M☉, radius 1.05 ± 0.03 R☉, age 4.42 ± 1.50 Gyr, and effective temperature 5635 ± 62 K. Light curves from Transiting Exoplanet Survey Satellite and Las Cumbres Observatory Global Telescope show a transiting sub-Neptune with a 2.23-d period, mass Mb = 8.90+−00.9695 M and radius Rb = 2.46+−00.1213 R. This is a rare ‘hot Neptune’ that falls within the parameter spaces known as the ‘Neptunian Desert’ and the ‘Radius Valley’. Two more planetary signals are detected in HARPS (High Accuracy Radial velocity Planetary Searcher) radial velocities, revealing two non-transiting planets with minimum masses Mc = 7.46+−11.6243 M and Md = 9.06+−12.7807 M, and periods of 4.579 ± 0.004 and 8.67 ± 0.01 d. The eccentricities were poorly constrained by the HARPS data, with upper limits eb = 0.11, ec = 0.29, and ed = 0.24. However, dynamical simulations of the TOI-1117 system, suggest that the orbits must be nearly circular to be stable. The simulations also show that TOI-1117 b and c are likely to be in a near 2:1 resonance. The multiplanet nature of TOI-1117 makes it a more complex case for formation theories of the Neptunian Desert and Radius Valley, as current theories such as high-eccentricity migration are too turbulent to produce a stable, non-eccentric, and multiplanet system. Moreover, analysis of TOI-1117 b’s photoevaporation history found rocky core and H/He atmosphere models to be inconsistent with observations, whilst water-rich scenarios were favoured.
KW - planets
KW - satellites: detection
KW - techniques: photometric
KW - techniques: radial velocities
UR - https://www.scopus.com/pages/publications/105010226164
UR - https://www.scopus.com/pages/publications/105010226164#tab=citedBy
U2 - 10.1093/mnras/staf939
DO - 10.1093/mnras/staf939
M3 - Article
AN - SCOPUS:105010226164
SN - 0035-8711
VL - 541
SP - 919
EP - 938
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -