Volume 650, June 2021
|Number of page(s)||13|
|Section||Interstellar and circumstellar matter|
|Published online||02 June 2021|
Simulating observable structures due to a perturbed interstellar medium in front of astrospheric bow shocks in 3D MHD
Ruhr-Universität Bochum, Fakultät für Physik und Astronomie, Institut für Theoretische Physik IV,
2 Ruhr-Universität Bochum, Research Department, Plasmas with Complex Interactions, 44780 Bochum, Germany
3 Ruhr Astroparticle and Plasma Physics (RAPP) Center, 44780 Bochum, Germany
4 Ruhr-Universität Bochum, Fakultät für Physik und Astronomie, Astronomisches Institut, 44780 Bochum, Germany
Accepted: 26 March 2021
Context. While the shapes of many observed bow shocks can be reproduced by simple astrosphere models, more elaborate approaches have recently been used to explain differing observable structures.
Aims. By placing perturbations of an otherwise homogeneous interstellar medium in front of the astrospheric bow shock of the runaway blue supergiant λ Cephei, the observable structure of the model astrosphere is significantly altered, providing insight into the origin of perturbed bow shock images.
Methods. Three-dimensional single-fluid magnetohydrodynamic (MHD) models of stationary astrospheres were subjected to various types of perturbations and simulated until stationarity was reached again. As examples, simple perturbations of the available MHD parameters (number density, bulk velocity, temperature, and magnetic field) as well as a more complex perturbation were chosen. Synthetic observations were generated by line-of-sight integration of the model data, producing Hα, 70 μm dust emission, and bremsstrahlung maps of the perturbed astrosphere’s evolution.
Results. The resulting shock structures and observational images differ strongly depending on the type of the injected perturbation and the viewing angles, forming arc-like protrusions or bifurcations of the bow shock structure, as well as rings, arcs, and irregular structures detached from the bow shock.
Key words: stars: winds, outflows / magnetohydrodynamics (MHD) / shock waves
© ESO 2021
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