تقرير
A High-Resolution Non-Detection of Escaping Helium In The Ultra-Hot Neptune LTT 9779b: Evidence for Weakened Evaporation
| العنوان: | A High-Resolution Non-Detection of Escaping Helium In The Ultra-Hot Neptune LTT 9779b: Evidence for Weakened Evaporation |
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| المؤلفون: | 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 |
| سنة النشر: | 2024 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Earth and Planetary Astrophysics |
| الوصف: | 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$\sigma$ upper limit of 0.12% ($\delta R_p/H < 14$) and a 3$\sigma$ upper limit of 0.20% ($\delta R_p/H < 22$). 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. Comment: 11 pages, 3 figures, accepted for publication in ApJL |
| نوع الوثيقة: | Working Paper |
| الوصول الحر: | http://arxiv.org/abs/2401.16474Test |
| رقم الانضمام: | edsarx.2401.16474 |
| قاعدة البيانات: | arXiv |
| الوصف غير متاح. |