Affiliation:
1. School of Physics, Trinity College Dublin, the University of Dublin, College Green, Dublin-2, D02 PN40, Ireland
Abstract
ABSTRACT
Strong atmospheric escape has been detected in several close-in exoplanets. As these planets consist mostly of hydrogen, observations in hydrogen lines, such as Ly α and H α, are powerful diagnostics of escape. Here, we simulate the evolution of atmospheric escape of close-in giant planets and calculate their associated Ly α and H α transits. We use a 1D hydrodynamic escape model to compute physical properties of the atmosphere and a ray tracing technique to simulate spectroscopic transits. We consider giant (0.3 and 1 Mjup) planets orbiting a solar-like star at 0.045 au, evolving from 10 to 5000 Myr. We find that younger giants show higher rates of escape, owing to a favourable combination of higher irradiation fluxes and weaker gravities. Less massive planets show higher escape rates (1010–1013 g s−1) than those more massive (109–1012 g s−1) over their evolution. We estimate that the 1-Mjup planet would lose at most 1 per cent of its initial mass due to escape, while the 0.3-Mjup planet, could lose up to 20 per cent. This supports the idea that the Neptunian desert has been formed due to significant mass-loss in low-gravity planets. At younger ages, we find that the mid-transit Ly α line is saturated at line centre, while H α exhibits transit depths of at most 3–4 per cent in excess of their geometric transit. While at older ages, Ly α absorption is still significant (and possibly saturated for the lower mass planet), the H α absorption nearly disappears. This is because the extended atmosphere of neutral hydrogen becomes predominantly in the ground state after ∼1.2 Gyr.
Funder
Irish Research Council Consolidator Laureate Award 2018
George Mason University
University of Michigan
University of Cambridge
NASA Goddard Space Flight Center
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
33 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献