TY - JOUR
T1 - A Hydrodynamic Study of the Escape of Metal Species and Excited Hydrogen from the Atmosphere of the Hot Jupiter WASP-121b
AU - Huang, Chenliang
AU - Koskinen, Tommi
AU - Lavvas, Panayotis
AU - Fossati, Luca
N1 - Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/7/1
Y1 - 2023/7/1
N2 - In the near-UV and optical transmission spectrum of the hot Jupiter WASP-121b, recent observations have detected strong absorption features of Mg, Fe, Ca, and Hα, extending outside of the planet’s Roche lobe. Studying these atomic signatures can directly trace the escaping atmosphere and constrain the energy balance of the upper atmosphere. To understand these features, we introduce a detailed forward model by expanding the capability of a one-dimensional model of the upper atmosphere and hydrodynamic escape to include important processes of atomic metal species. The hydrodynamic model is coupled to a Lyα Monte Carlo radiative transfer calculation to simulate the excited hydrogen population and associated heating/ionization effects. Using this model, we interpret the detected atomic features in the transmission spectrum of WASP-121b and explore the impact of metals and excited hydrogen on its upper atmosphere. We demonstrate the use of multiple absorption lines to impose stronger constraints on the properties of the upper atmosphere than the analysis of a single transmission feature can provide. In addition, the model shows that line broadening due to atmospheric outflow driven by Roche lobe overflow is necessary to explain the observed line widths and highlights the importance of the high mass-loss rate caused by Roche lobe overflow, which requires careful consideration of the structure of the lower and middle atmosphere. We also show that metal species and excited-state hydrogen can play an important role in the thermal and ionization balance of ultrahot Jupiter thermospheres.
AB - In the near-UV and optical transmission spectrum of the hot Jupiter WASP-121b, recent observations have detected strong absorption features of Mg, Fe, Ca, and Hα, extending outside of the planet’s Roche lobe. Studying these atomic signatures can directly trace the escaping atmosphere and constrain the energy balance of the upper atmosphere. To understand these features, we introduce a detailed forward model by expanding the capability of a one-dimensional model of the upper atmosphere and hydrodynamic escape to include important processes of atomic metal species. The hydrodynamic model is coupled to a Lyα Monte Carlo radiative transfer calculation to simulate the excited hydrogen population and associated heating/ionization effects. Using this model, we interpret the detected atomic features in the transmission spectrum of WASP-121b and explore the impact of metals and excited hydrogen on its upper atmosphere. We demonstrate the use of multiple absorption lines to impose stronger constraints on the properties of the upper atmosphere than the analysis of a single transmission feature can provide. In addition, the model shows that line broadening due to atmospheric outflow driven by Roche lobe overflow is necessary to explain the observed line widths and highlights the importance of the high mass-loss rate caused by Roche lobe overflow, which requires careful consideration of the structure of the lower and middle atmosphere. We also show that metal species and excited-state hydrogen can play an important role in the thermal and ionization balance of ultrahot Jupiter thermospheres.
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U2 - 10.3847/1538-4357/accd5e
DO - 10.3847/1538-4357/accd5e
M3 - Article
AN - SCOPUS:85165192023
SN - 0004-637X
VL - 951
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 123
ER -