Imaging Magnetically Driven Astrospheres: A Forward Modeling Approach

Le résumé fourni par la source

Abstract An astrosphere is a vast, tailed, bubble-like volume around a star, formed through the interaction between the stellar magnetic field, the stellar wind, and the interstellar medium (ISM). Detecting and characterizing astrospheres is essential for constraining stellar wind properties, understanding stellar evolution, and assessing the habitability of surrounding exoplanetary systems. Charge exchanges between ionized stellar wind particles and cold ISM hydrogen atoms populate the astrosphere with neutral hydrogen, which leaves observable signatures in the Ly α ​​​​line absorption profile. Previous studies have inferred stellar mass-loss rates by measuring Ly α absorption in stellar spectra caused by astrospheric neutral hydrogen. However, our knowledge of the global morphology of astrospheres remains limited and largely dependent on sometimes contradictory simulations. With a three-dimensional magnetohydrodynamic astrosphere model, we perform forward modeling of the Ly α emission generated by resonant scattering from neutral hydrogen surrounding the star and constract a two-dimensional (2D) map of the astrosphere. Results show that the modeled emission intensity can potentially exceed the observational limits of the Hubble Space Telescope (HST). The 2D astrospheric maps are sensitive to varied line-of-sight orientations and averaged ISM velocity along the line of sight. The spatially resolved circumstellar Ly α emission could provide important constraints on the astrospheric configuration and stellar wind properties, such as the bow-shock standing distance, the stellar wind symmetry, and the shape of the astrotail. Our results highlight Ly α astrosphere detections as a promising science case for HST and future missions such as the Habitable Worlds Observatory.

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