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arXiv · 2403.17325

A possibly solar metallicity atmosphere escaping from HAT-P-32b revealed by H$α$ and He absorption

Dongdong Yan·Jianheng Guo·Kwang-il Seon·Manuel López-Puertas·Stefan Czesla·Manuel Lampón
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Abstract

This paper presents a hydrodynamic simulation that couples detailed non-local thermodynamic equilibrium (NLTE) calculations of the hydrogen and helium level populations to model the H$α$ and He 10830 transmission spectra of the hot Jupiter HAT-P-32b. A Monte Carlo simulation is applied to calculate the number of Ly$α$ resonance scatterings, which is the main process for populating H(2). In the examined parameter space, only the models with H/He $\geq$ 99.5/0.5, $(0.5 \sim 3.0)$ times the fiducial value of $F_{\rm XUV}$, $β_m = 0.16\sim 0.3$, can explain the H$α$ and He 10830 lines simultaneously. We find a mass-loss rate of $\sim (1.0\sim 3.1) \times 10^{13}$ g s$^{-1}$, consistent with previous studies. Moreover, we find that the stellar Ly$α$ flux should be as high as $4 \times 10^{5}$ erg cm$^{-2}$ s$^{-1}$, indicating high stellar activity during the observation epoch of the two absorption lines. Despite the fact that the metallicity in the lower atmosphere of HAT-P-32b may be super-solar, our simulations tentatively suggest it is close to solar in the upper atmosphere. The difference in metallicity between the lower and upper atmospheres is essential for future atmospheric characterisations.

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Dongdong Yan, Jianheng Guo, Kwang-il Seon, Manuel López-Puertas, Stefan Czesla, Manuel Lampón. 2024-03-26. A possibly solar metallicity atmosphere escaping from HAT-P-32b revealed by H$α$ and He absorption. https://arxiv.org/abs/2403.17325

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