English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The metastable Helium (He*) lines near $10830~{\rm A}$ are ideal probes ofatmospheric erosion--a common phenomenon of close-in exoplanet evolution. Ahandful of exoplanet observations yielded well-resolved He* absorption featuresin transits, yet they were mostly analyzed with 1D isothermal modelsprescribing mass-loss rates. This work devises 3D hydrodynamics co-evolved withray-tracing radiative transfer and non-equilibrium thermochemsitry. Startingfrom the observed stellar/planetary properties with reasonable assumptionsabout the host's high energy irradiation, we predict from first principle themass loss rate, the temperature and ionization profiles, and 3D outflowkinematics. Our simulations well reproduce the observed He* line profiles andlight curves of WASP-69b. We further investigate the dependence of He*observables on simulation conditions and host radiation. The key findings are:(1) Simulations reveal a photoevaporative outflow ($\sim 0.5~M_{\oplus}~{\rmGyr}^{-1}$) for WASP-69b without a prominent comet-like tail, consistent withthe symmetric transit shape (Vissapragada et al. 2020). (2) 3D simulations aremandatory for hydrodynamic features, including Coriolis force, advection, andkinematic line broadening. (3) EUV ($>13.6~{\rm eV}$) photons dominatephotoevaporative outflows and populate He* via recombination; FUV is alsodetrimental by destroying He*; X-ray plays a secondary role. (4) K stars hitthe sweet spot of EUV/FUV balance for He* line observation, while G and M starsare also worthy targets. (5) Stellar flars create characteristic responses inthe He* line profiles.

astrophysical journal/the astrophysical journal

Metastable Helium Absorptions with 3D Hydrodynamics and Self-Consistent  Photochemistry I: WASP-69b, Dimensionality, XUV Flux Level, Spectral Types,  and Flares