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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2510.11490 |
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| author | Bonomo, A. S. Naponiello, L. Sozzetti, A. Benatti, S. Carleo, I. Biazzo, K. Cubillos, P. E. Damasso, M. Di Maio, C. Dorn, C. Hara, N. Polychroni, D. Steinmeyer, M. -L. Collins, K. A. Desidera, S. Dumusque, X. Lanza, A. F. Safonov, B. S. Stockdale, C. Turrini, D. Ziegler, C. Affer, L. D'Arpa, M. Fardella, V. Harutyunyan, A. Lorenzi, V. Malavolta, L. Mancini, L. Mantovan, G. Micela, G. Murgas, F. Nardiello, D. Pagano, I. Pallé, E. Pedani, M. Pinamonti, M. Rainer, M. Scandariato, G. Spinelli, R. Zingales, T. |
| author_facet | Bonomo, A. S. Naponiello, L. Sozzetti, A. Benatti, S. Carleo, I. Biazzo, K. Cubillos, P. E. Damasso, M. Di Maio, C. Dorn, C. Hara, N. Polychroni, D. Steinmeyer, M. -L. Collins, K. A. Desidera, S. Dumusque, X. Lanza, A. F. Safonov, B. S. Stockdale, C. Turrini, D. Ziegler, C. Affer, L. D'Arpa, M. Fardella, V. Harutyunyan, A. Lorenzi, V. Malavolta, L. Mancini, L. Mantovan, G. Micela, G. Murgas, F. Nardiello, D. Pagano, I. Pallé, E. Pedani, M. Pinamonti, M. Rainer, M. Scandariato, G. Spinelli, R. Zingales, T. |
| contents | Sub-Neptunes with planetary radii of $R_{p} \simeq 2-4 R_{\oplus}$ are the most common planets around solar-type stars in short-period ($P<100$ d) orbits. It is still unclear, however, what their most likely composition is, that is whether they are predominantly gas dwarfs or water worlds. The sub-Neptunes orbiting bright host stars are very valuable because they are suitable for atmospheric characterization, which can break the well-known degeneracy in planet composition from the planet bulk density, when combined with a precise and accurate mass measurement. Here we report on the characterization of the sub-Neptune TOI-5789 c, which transits in front of the bright ($V=7.3$ mag and $K_{s}=5.35$ mag) and magnetically inactive K1V dwarf HIP 99452 every 12.93 days, thanks to TESS photometry and 141 high-precision radial velocities obtained with the HARPS-N spectrograph. We find that its radius, mass, and bulk density are $R_{c}=2.86^{+0.18}_{-0.15} R_\oplus$, $M_{c}=5.00 \pm 0.50 M_\oplus$, and $ρ_{c}=1.16 \pm 0.23$ g cm$^{-3}$, and we show that TOI-5789 c is a promising target for atmospheric characterization with both JWST and, in the future, Ariel. By analyzing the HARPS-N radial velocities with different tools, we also detected three additional non-transiting planets, namely TOI-5789 b, d, and e, with orbital periods and minimum masses of $P_{b}=2.76$ d, $M_{b}\sin{i}=2.12 \pm 0.28 M_\oplus$, $P_{d}=29.6$ d, $M_{d}\sin{i}=4.29 \pm 0.68 M_\oplus$, and $P_{e}=63.0$ d, $M_{e}\sin{i}=11.61 \pm 0.97 M_\oplus$. TOI-5789 is a mutually inclined system as the difference between the orbital inclinations of planets b and c must be higher than $\sim4$ deg. Nevertheless, from sensitivity studies based on both the HARPS-N and archival HIRES radial-velocity measurements, we can exclude that these relatively high mutual inclinations are due to the perturbation by an outer gaseous giant planet. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_11490 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The GAPS programme at TNG LXXI. A sub-Neptune suitable for atmospheric characterization in a multiplanet and mutually inclined system orbiting the bright K dwarf TOI-5789 (HIP 99452) Bonomo, A. S. Naponiello, L. Sozzetti, A. Benatti, S. Carleo, I. Biazzo, K. Cubillos, P. E. Damasso, M. Di Maio, C. Dorn, C. Hara, N. Polychroni, D. Steinmeyer, M. -L. Collins, K. A. Desidera, S. Dumusque, X. Lanza, A. F. Safonov, B. S. Stockdale, C. Turrini, D. Ziegler, C. Affer, L. D'Arpa, M. Fardella, V. Harutyunyan, A. Lorenzi, V. Malavolta, L. Mancini, L. Mantovan, G. Micela, G. Murgas, F. Nardiello, D. Pagano, I. Pallé, E. Pedani, M. Pinamonti, M. Rainer, M. Scandariato, G. Spinelli, R. Zingales, T. Earth and Planetary Astrophysics Solar and Stellar Astrophysics Sub-Neptunes with planetary radii of $R_{p} \simeq 2-4 R_{\oplus}$ are the most common planets around solar-type stars in short-period ($P<100$ d) orbits. It is still unclear, however, what their most likely composition is, that is whether they are predominantly gas dwarfs or water worlds. The sub-Neptunes orbiting bright host stars are very valuable because they are suitable for atmospheric characterization, which can break the well-known degeneracy in planet composition from the planet bulk density, when combined with a precise and accurate mass measurement. Here we report on the characterization of the sub-Neptune TOI-5789 c, which transits in front of the bright ($V=7.3$ mag and $K_{s}=5.35$ mag) and magnetically inactive K1V dwarf HIP 99452 every 12.93 days, thanks to TESS photometry and 141 high-precision radial velocities obtained with the HARPS-N spectrograph. We find that its radius, mass, and bulk density are $R_{c}=2.86^{+0.18}_{-0.15} R_\oplus$, $M_{c}=5.00 \pm 0.50 M_\oplus$, and $ρ_{c}=1.16 \pm 0.23$ g cm$^{-3}$, and we show that TOI-5789 c is a promising target for atmospheric characterization with both JWST and, in the future, Ariel. By analyzing the HARPS-N radial velocities with different tools, we also detected three additional non-transiting planets, namely TOI-5789 b, d, and e, with orbital periods and minimum masses of $P_{b}=2.76$ d, $M_{b}\sin{i}=2.12 \pm 0.28 M_\oplus$, $P_{d}=29.6$ d, $M_{d}\sin{i}=4.29 \pm 0.68 M_\oplus$, and $P_{e}=63.0$ d, $M_{e}\sin{i}=11.61 \pm 0.97 M_\oplus$. TOI-5789 is a mutually inclined system as the difference between the orbital inclinations of planets b and c must be higher than $\sim4$ deg. Nevertheless, from sensitivity studies based on both the HARPS-N and archival HIRES radial-velocity measurements, we can exclude that these relatively high mutual inclinations are due to the perturbation by an outer gaseous giant planet. |
| title | The GAPS programme at TNG LXXI. A sub-Neptune suitable for atmospheric characterization in a multiplanet and mutually inclined system orbiting the bright K dwarf TOI-5789 (HIP 99452) |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2510.11490 |