恒星物理研究组知识库

Escaping atmosphere has been detected by the excess absorption of Ly alpha, H alpha and He triplet (lambda 10830) lines. Simultaneously modeling the absorption of the H alpha and He lambda 10830 lines can provide useful constraints about the exoplanetary atmosphere. In this paper, we use a hydrodynamic model combined with a non-local thermodynamic model and a new Monte Carlo simulation model to obtain the H(2) and He(2(3) S) populations. The Monte Carlo simulations of Ly alpha radiative transfer are performed with assumptions of a spherical stellar Ly alpha radiation and a spherical planetary atmosphere, for the first time, to calculate the Ly alpha mean intensity distribution inside the planetary atmosphere, necessary in estimating the H(2) population. We model the transmission spectra of the H alpha and He lambda 10830 lines simultaneously in hot Jupiter WASP-52b. We find that models with many different H/He ratios can reproduce the H alpha observations well if the host star has (1) a high X-ray and extreme-ultraviolet (XUV) flux (F (XUV)) and a relatively low X-ray fraction in XUV radiation (beta ( m )) or (2) a low F (XUV) and a high beta ( m ). The simulations of the He lambda 10830 triplet suggest that a high H/He ratio (similar to 98/2) is required to fit the observation. The models that fit both lines well confine F (XUV) to be about 0.5 times the fiducial value and beta ( m ) to have a value around 0.3. The models also suggest that hydrogen and helium originate from the escaping atmosphere, and the mass-loss rate is about 2.8 x 10(11) g s(-1).