Moving inhomogeneous envelopes of stars

Abstract

Massive stars are extremely luminous and drive strong winds, blowing a large part of their matter into the galactic environment before they finally explode as a supernova. Quantitative knowledge of massive star feedback is required to understand our Universe as we see it. Traditionally, massive stars have been studied under the assumption that their winds are homogeneous and stationary, largely relying on the Sobolev approximation. However, observations with the newest instruments, together with progress in

The X-ray catalog of spectroscopically identified Galactic O stars

“…Among the main problems affecting empirical measurements of mass-loss rates in O stars is stellar wind clumping. Significant effort has been dedicated to evaluating the effects of wind inhomogeneity on spectral analysis and to improve model stellar atmospheres (see e.g., Oskinova et al 2016). The current understanding is that the in case of O supergiants, the theoretical recipes (Vink et al 2000) predict mass-loss rates that are ∼1.5−3 times higher than those obtained from spectroscopic analyses that include the effects of optically thin ("microclumping") as well as optically thick clumping ("macroclumping"; e.g., Oskinova et al 2007;Sundqvist et al 2011;Šurlan et al 2012;Shenar et al 2015).…”

The effect of horizontal plasma inhomogeneities in 3D NLTE radiation transfer in stellar atmospheres

“…Typical examples are studies of clumping in stellar atmospheres and winds, where the inhomo-geneities are believed to be a consequence of radiative-acoustic instability (Owocki et al 1988, see also the review Sundqvist et al 2012), adiabatic fluctuations (Chiueh, 1997) or subphotospheric convection (Cantiello et al, 2009). As it was shown byŠurlan et al (2012,2013) (see also Oskinova et al, 2016), proper 3D treatment of inhomogeneities is necessary to take into account both opticaly thin and optically thick clumps.…”