The TOI-1117 Multi-planetary System: 3 sub-Neptunes, 1 in both the Neptunian Desert and Radius Valley
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| Format: | Preprint |
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2025
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| author | Lockley, Isobel S. Armstrong, David J. Fernández, Jorge Fernández Millholland, Sarah Knierim, Henrik Mena, Elisa Delgado Sousa, Sergio Collins, Karen A. Watkins, Cristilyn N. Howell, Steve B. Adibekyan, Vardan Helled, Ravit Ziegler, Carl Bayliss, Daniel Briceño, César Castro-González, Amadeo Clark, Catherine A. Collins, Kevin I. Christiansen, Jessie L. Cui, Kaiming Diaz, Rodrigo Jenkins, Jon M. Keniger, Marcelo A. F. Kunimoto, Michelle Law, Nicholas Lillo-Box, Jorge Littlefield, Colin Mann, Andrew W. Mitchell, Morgan A. Nielsen, Louise D. Rodrigues, José Rowden, Pam Santos, Nuno C. Seager, Sara Wheatley, Peter J. Winn, Joshua |
| author_facet | Lockley, Isobel S. Armstrong, David J. Fernández, Jorge Fernández Millholland, Sarah Knierim, Henrik Mena, Elisa Delgado Sousa, Sergio Collins, Karen A. Watkins, Cristilyn N. Howell, Steve B. Adibekyan, Vardan Helled, Ravit Ziegler, Carl Bayliss, Daniel Briceño, César Castro-González, Amadeo Clark, Catherine A. Collins, Kevin I. Christiansen, Jessie L. Cui, Kaiming Diaz, Rodrigo Jenkins, Jon M. Keniger, Marcelo A. F. Kunimoto, Michelle Law, Nicholas Lillo-Box, Jorge Littlefield, Colin Mann, Andrew W. Mitchell, Morgan A. Nielsen, Louise D. Rodrigues, José Rowden, Pam Santos, Nuno C. Seager, Sara Wheatley, Peter J. Winn, Joshua |
| contents | We present the discovery of three sub-Neptune planets around TOI-1117, a Sun-like star with mass $0.97\pm0.02M_{\odot}$, radius $1.05\pm0.03R_{\odot}$, age $4.42\pm1.50$ Gyr and effective temperature $5635\pm62$ K. Light curves from TESS and LCOGT show a transiting sub-Neptune with a $2.23$ day period, mass $M_b=8.90_{-0.96}^{+0.95}M_{\oplus}$ and radius $R_b=2.46_{-0.12}^{+0.13}R_{\oplus}$. 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 radial velocities, revealing two non-transiting planets with minimum masses $M_c=7.46_{-1.62}^{+1.43}M_{\oplus}$ and $M_d=9.06_{-1.78}^{+2.07}M_{\oplus}$, and periods of $4.579\pm0.004$ and $8.67\pm0.01$ days. The eccentricities were poorly constrained by the HARPS data, with upper limits $e_b=0.11$, $e_c=0.29$, and $e_d=0.24$. 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-1117b and c are likely to be in a near 2:1 resonance. The multi-planet 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, multi-planet system. Moreover, analysis of TOI-1117b's photoevaporation history found rocky core and H/He atmosphere models to be inconsistent with observations, whilst water-rich scenarios were favoured. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_05521 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The TOI-1117 Multi-planetary System: 3 sub-Neptunes, 1 in both the Neptunian Desert and Radius Valley Lockley, Isobel S. Armstrong, David J. Fernández, Jorge Fernández Millholland, Sarah Knierim, Henrik Mena, Elisa Delgado Sousa, Sergio Collins, Karen A. Watkins, Cristilyn N. Howell, Steve B. Adibekyan, Vardan Helled, Ravit Ziegler, Carl Bayliss, Daniel Briceño, César Castro-González, Amadeo Clark, Catherine A. Collins, Kevin I. Christiansen, Jessie L. Cui, Kaiming Diaz, Rodrigo Jenkins, Jon M. Keniger, Marcelo A. F. Kunimoto, Michelle Law, Nicholas Lillo-Box, Jorge Littlefield, Colin Mann, Andrew W. Mitchell, Morgan A. Nielsen, Louise D. Rodrigues, José Rowden, Pam Santos, Nuno C. Seager, Sara Wheatley, Peter J. Winn, Joshua Earth and Planetary Astrophysics We present the discovery of three sub-Neptune planets around TOI-1117, a Sun-like star with mass $0.97\pm0.02M_{\odot}$, radius $1.05\pm0.03R_{\odot}$, age $4.42\pm1.50$ Gyr and effective temperature $5635\pm62$ K. Light curves from TESS and LCOGT show a transiting sub-Neptune with a $2.23$ day period, mass $M_b=8.90_{-0.96}^{+0.95}M_{\oplus}$ and radius $R_b=2.46_{-0.12}^{+0.13}R_{\oplus}$. 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 radial velocities, revealing two non-transiting planets with minimum masses $M_c=7.46_{-1.62}^{+1.43}M_{\oplus}$ and $M_d=9.06_{-1.78}^{+2.07}M_{\oplus}$, and periods of $4.579\pm0.004$ and $8.67\pm0.01$ days. The eccentricities were poorly constrained by the HARPS data, with upper limits $e_b=0.11$, $e_c=0.29$, and $e_d=0.24$. 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-1117b and c are likely to be in a near 2:1 resonance. The multi-planet 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, multi-planet system. Moreover, analysis of TOI-1117b's photoevaporation history found rocky core and H/He atmosphere models to be inconsistent with observations, whilst water-rich scenarios were favoured. |
| title | The TOI-1117 Multi-planetary System: 3 sub-Neptunes, 1 in both the Neptunian Desert and Radius Valley |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2506.05521 |