An Oasis in the Brown Dwarf Desert: Confirmation of Two Low-mass Transiting Brown Dwarfs Discovered by TESS
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| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Zhang, Elina Y. Carmichael, Theron W. Huber, Daniel Stassun, Keivan G. Fukui, Akihiko Narita, Norio Murgas, Felipe Palle, Enric Latham, David W. Calkins, Michael L. Seager, Sara Winn, Joshua N. Vezie, Michael Hounsell, Rebekah Osborn, Hugh P. Caldwell, Douglas A. Jenkins, Jon M. |
| author_facet | Zhang, Elina Y. Carmichael, Theron W. Huber, Daniel Stassun, Keivan G. Fukui, Akihiko Narita, Norio Murgas, Felipe Palle, Enric Latham, David W. Calkins, Michael L. Seager, Sara Winn, Joshua N. Vezie, Michael Hounsell, Rebekah Osborn, Hugh P. Caldwell, Douglas A. Jenkins, Jon M. |
| contents | As the intermediate-mass siblings of stars and planets, brown dwarfs (BDs) are vital to study for a better understanding of how objects change across the planet-to-star mass range. Here, we report two low-mass transiting BD systems discovered by TESS, TOI-4776 (TIC 196286578) and TOI-5422 (TIC 80611440), located in an under-populated region of the BD mass-period space. These two systems have comparable masses but different ages. The younger and larger BD is TOI-4776b with $32.0^{+1.9}_{-1.8}M_{Jup}$ and $1.018^{+0.048}_{-0.043}R_{Jup}$, orbiting a late-F star about $5.4^{+2.8}_{-2.2}$ Gyr old in a 10.4138$\pm$0.000014 day period. The older TOI-5422b has $27.7^{+1.4}_{-1.1}M_{Jup}$ and $0.815^{+0.031}_{-0.026}R_{Jup}$ in a 5.3772$\pm$0.00001 day orbit around a subgiant star about $8.2\pm2.4$ Gyr old. Compared with substellar mass-radius (M-R) evolution models, TOI-4776b has an inflated radii. In contrast, TOI-5422b is slightly "underluminous" with respect to model predictions, which is not commonly seen in the BD population. In addition, TOI-5422 shows apparent photometric modulations with a rotation period of 10.75$\pm$0.54 day found by rotation analysis, and the stellar inclination angle is obtained to be $I_{\star}=75.52^{+9.96}_{-11.79}$$^{\circ}$. Therefore, it is likely that TOI-5422b is spinning up the host star and its orbit is aligned with the stellar spin axis. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_05115 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | An Oasis in the Brown Dwarf Desert: Confirmation of Two Low-mass Transiting Brown Dwarfs Discovered by TESS Zhang, Elina Y. Carmichael, Theron W. Huber, Daniel Stassun, Keivan G. Fukui, Akihiko Narita, Norio Murgas, Felipe Palle, Enric Latham, David W. Calkins, Michael L. Seager, Sara Winn, Joshua N. Vezie, Michael Hounsell, Rebekah Osborn, Hugh P. Caldwell, Douglas A. Jenkins, Jon M. Solar and Stellar Astrophysics Earth and Planetary Astrophysics As the intermediate-mass siblings of stars and planets, brown dwarfs (BDs) are vital to study for a better understanding of how objects change across the planet-to-star mass range. Here, we report two low-mass transiting BD systems discovered by TESS, TOI-4776 (TIC 196286578) and TOI-5422 (TIC 80611440), located in an under-populated region of the BD mass-period space. These two systems have comparable masses but different ages. The younger and larger BD is TOI-4776b with $32.0^{+1.9}_{-1.8}M_{Jup}$ and $1.018^{+0.048}_{-0.043}R_{Jup}$, orbiting a late-F star about $5.4^{+2.8}_{-2.2}$ Gyr old in a 10.4138$\pm$0.000014 day period. The older TOI-5422b has $27.7^{+1.4}_{-1.1}M_{Jup}$ and $0.815^{+0.031}_{-0.026}R_{Jup}$ in a 5.3772$\pm$0.00001 day orbit around a subgiant star about $8.2\pm2.4$ Gyr old. Compared with substellar mass-radius (M-R) evolution models, TOI-4776b has an inflated radii. In contrast, TOI-5422b is slightly "underluminous" with respect to model predictions, which is not commonly seen in the BD population. In addition, TOI-5422 shows apparent photometric modulations with a rotation period of 10.75$\pm$0.54 day found by rotation analysis, and the stellar inclination angle is obtained to be $I_{\star}=75.52^{+9.96}_{-11.79}$$^{\circ}$. Therefore, it is likely that TOI-5422b is spinning up the host star and its orbit is aligned with the stellar spin axis. |
| title | An Oasis in the Brown Dwarf Desert: Confirmation of Two Low-mass Transiting Brown Dwarfs Discovered by TESS |
| topic | Solar and Stellar Astrophysics Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2503.05115 |