Morphology of Hydrodynamic Winds: A Study of Planetary Winds in Stellar Environments
AffiliationUniv Arizona, Dept Astron
Univ Arizona, Steward Observ
planets and satellites: atmospheres
planets and satellites: gaseous planets
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationJohn McCann et al 2019 ApJ 873 89
Rights© 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractBathed in intense ionizing radiation, close-in gaseous planets undergo hydrodynamic atmospheric escape, which ejects the upper extent of their atmospheres into the interplanetary medium. Ultraviolet detections of escaping gas around transiting planets corroborate such a framework. Exposed to the stellar environment, the outflow is shaped by its interaction with the stellar wind and by the planet's orbit. We model these effects using Athena to perform 3D radiative-hydrodynamic simulations of tidally locked hydrogen atmospheres receiving large amounts of ionizing extreme-ultraviolet flux in various stellar environments for the low-magnetic-field case. Through a step-by-step exploration of orbital and stellar wind effects on the planetary outflow, we find three structurally distinct stellar wind regimes: weak, intermediate, and strong. We perform synthetic Ly alpha observations and find unique observational signatures for each regime. A weak stellar wind-which cannot confine the planetary outflow, leading to a torus of material around the star-has a pretransit, redshifted dayside arm and a slightly redward-skewed spectrum during transit. The intermediate regime truncates the dayside outflow at large distances from the planet and causes periodic disruptions of the outflow, producing observational signatures that mimic a double transit. The first of these dips is blueshifted and precedes the optical transit. Finally, strong stellar winds completely confine the outflow into a cometary tail and accelerate the outflow outward, producing large blueshifted signals posttransit. Across all three regimes, large signals occur far outside of transit, offering motivation to continue ultraviolet observations outside of direct transit.
VersionFinal published version
SponsorsNational Science Foundation [AST-1411536, -1228509]; Australian Research Council [FT180100375]