ﻻ يوجد ملخص باللغة العربية
A significative fraction of all massive stars in the Milky Way move supersonically through their local interstellar medium (ISM), producing bow shock nebulae by wind-ISM interaction. The stability of these observed astrospheres around cool massive stars challenges precedent two-dimensional (magneto-)hydrodynamical simulations of their surroundings. We present three-dimensional magneto-hydrodynamical (3D MHD) simulations of the circumstellar medium of runaway M-type red supergiant stars moving with velocity v_star= 50 km/s. We treat the stellar wind with a Parker spiral and assume a 7 microG magnetisation of the ISM. Our free parameter is the angle theta_mag between ISM flow and magnetisation, taken to 0, 45 and 90 degrees. It is found that simulation dimension, coordinate systems and grid effects can greatly affect the development of the modelled astrospheres. Nevertheless, as soon as the ISM flow and magnetisation directions differs by more than a few degrees (theta_mag>5 degree), the bow shock is stabilised, most clumpiness and ragged structures vanishing. The complex shape of the bowshocks induce important projection effects, e.g. at optical Ha line, producing complex of astrospheric morphologies. We speculate that those effects are also at work around earlier-type massive stars, which would explain their diversity of their observed arc-like nebula around runaway OB stars. Our 3D MHD models are fitting well observations of the astrospheres of several runaway red supergiant stars. The results interpret the smoothed astrosphere of IRC-10414 and Betelgeuse aOri) are stabilised by an organised, non-parallel ambient magnetic field. Our findings suggest that IRC-10414 is currently in a steady state of its evolution, and that Betelgeuses bar is of interstellar origin.
The interpretation of recent observations of bow shocks around O-stars and the creation of corresponding models require a detailed understanding of the associated (magneto-)hydrodynamic structures. We base our study on three-dimensional numerical mag
A significant fraction of massive stars are moving supersonically through the interstellar medium (ISM), either due to disruption of a binary system or ejection from their parent star cluster. The interaction of their wind with the ISM produces a bow
We present optical spectrophotometry of the red supergiant Betelgeuse from 2020 February 15, during its recent unprecedented dimming episode. By comparing this spectrum to stellar atmosphere models for cool supergiants, as well as spectrophotometry o
The nearby red supergiant (RSG) Betelgeuse has a complex circumstellar medium out to at least 0.5 parsecs from its surface, shaped by its mass-loss history within the past 0.1 Myr, its environment, and its motion through the interstellar medium (ISM)
Large millimeter interferometers are revealing a growing number of rotating outflows, which are suggested to trace magneto-centrifugal disk winds (MHD DWs). However, their impact on disk accretion is not yet well quantified. Here we identify systemat