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| Autores principales: | , , , , , , , , , , , , , , , , , , |
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| Formato: | Preprint |
| Publicado: |
2024
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| Materias: | |
| Acceso en línea: | https://arxiv.org/abs/2401.16474 |
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| _version_ | 1866913214966530048 |
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| author | Vissapragada, Shreyas McCreery, Patrick Santos, Leonardo A. Dos Espinoza, Néstor McWilliam, Andrew Matsunaga, Noriyuki Redai, Jéa Adams Behr, Patrick France, Kevin Hamano, Satoshi Hull, Charlie Ikeda, Yuji Katoh, Haruki Kawakita, Hideyo López-Morales, Mercedes Ceballos, Kevin N. Ortiz Otsubo, Shogo Sarugaku, Yuki Takeuchi, Tomomi |
| author_facet | Vissapragada, Shreyas McCreery, Patrick Santos, Leonardo A. Dos Espinoza, Néstor McWilliam, Andrew Matsunaga, Noriyuki Redai, Jéa Adams Behr, Patrick France, Kevin Hamano, Satoshi Hull, Charlie Ikeda, Yuji Katoh, Haruki Kawakita, Hideyo López-Morales, Mercedes Ceballos, Kevin N. Ortiz Otsubo, Shogo Sarugaku, Yuki Takeuchi, Tomomi |
| contents | The recent discovery of ``ultra-hot'' ($P < 1$ day) Neptunes has come as a surprise: some of these planets have managed to retain gaseous envelopes despite being close enough to their host stars to trigger strong photoevaporation and/or Roche lobe overflow. Here, we investigate atmospheric escape in LTT 9779b, an ultra-hot Neptune with a volatile-rich envelope. We observed two transits of this planet using the newly-commissioned WINERED spectrograph ($R\sim68,000$) on the 6.5 m Clay/Magellan II Telescope, aiming to detect an extended upper atmosphere in the He 10830 A triplet. We found no detectable planetary absorption: in a 0.75 A passband centered on the triplet, we set a 2$σ$ upper limit of 0.12% ($δR_p/H < 14$) and a 3$σ$ upper limit of 0.20% ($δR_p/H < 22$). Using a H/He isothermal Parker wind model, we found corresponding 95% and 99.7% upper limits on the planetary mass-loss rate of $\dot{M} < 10^{10.03}$ g s$^{-1}$ and $\dot{M} < 10^{11.11}$ g s$^{-1}$ respectively, smaller than predicted by outflow models even considering the weak stellar XUV emission. The low evaporation rate is plausibly explained by a metal-rich envelope, which would decrease the atmospheric scale height and increase the cooling rate of the outflow. This hypothesis is imminently testable: if metals commonly weaken planetary outflows, then we expect that \textit{JWST} will find high atmospheric metallicities for small planets that have evaded detection in He 10830 A. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2401_16474 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | A High-Resolution Non-Detection of Escaping Helium In The Ultra-Hot Neptune LTT 9779b: Evidence for Weakened Evaporation Vissapragada, Shreyas McCreery, Patrick Santos, Leonardo A. Dos Espinoza, Néstor McWilliam, Andrew Matsunaga, Noriyuki Redai, Jéa Adams Behr, Patrick France, Kevin Hamano, Satoshi Hull, Charlie Ikeda, Yuji Katoh, Haruki Kawakita, Hideyo López-Morales, Mercedes Ceballos, Kevin N. Ortiz Otsubo, Shogo Sarugaku, Yuki Takeuchi, Tomomi Earth and Planetary Astrophysics The recent discovery of ``ultra-hot'' ($P < 1$ day) Neptunes has come as a surprise: some of these planets have managed to retain gaseous envelopes despite being close enough to their host stars to trigger strong photoevaporation and/or Roche lobe overflow. Here, we investigate atmospheric escape in LTT 9779b, an ultra-hot Neptune with a volatile-rich envelope. We observed two transits of this planet using the newly-commissioned WINERED spectrograph ($R\sim68,000$) on the 6.5 m Clay/Magellan II Telescope, aiming to detect an extended upper atmosphere in the He 10830 A triplet. We found no detectable planetary absorption: in a 0.75 A passband centered on the triplet, we set a 2$σ$ upper limit of 0.12% ($δR_p/H < 14$) and a 3$σ$ upper limit of 0.20% ($δR_p/H < 22$). Using a H/He isothermal Parker wind model, we found corresponding 95% and 99.7% upper limits on the planetary mass-loss rate of $\dot{M} < 10^{10.03}$ g s$^{-1}$ and $\dot{M} < 10^{11.11}$ g s$^{-1}$ respectively, smaller than predicted by outflow models even considering the weak stellar XUV emission. The low evaporation rate is plausibly explained by a metal-rich envelope, which would decrease the atmospheric scale height and increase the cooling rate of the outflow. This hypothesis is imminently testable: if metals commonly weaken planetary outflows, then we expect that \textit{JWST} will find high atmospheric metallicities for small planets that have evaded detection in He 10830 A. |
| title | A High-Resolution Non-Detection of Escaping Helium In The Ultra-Hot Neptune LTT 9779b: Evidence for Weakened Evaporation |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2401.16474 |