Applications of

Radiative Transfer

to stellar and planetary atmospheres
Tenerife, Spain - 13-17 Nov. 2017

Poster abstract details

HERSCHEL-PACS: Constrains for clumping in the intermediate wind regions of OB stars
M. M. Rubio-Díez, J. O. Sundqvist, F. Najarro, A. Traficante, J. Puls, and L. Calzolleti


We examine the radial stratification of wind clumping and derive upper limits of mass-loss rates for a sample of 24 Galactic OB-stars, using new far-infrared (\textit{Herschel}/PACS} observations together with archival data from near infrared to radio wavelengths.
We use our density-squared diagnostic tools to derive $\dot{M} \sqrt{f_{cl}^{min}}$, where $f_{cl}^{min}$ is the minimum value of the radially dependent clumping factor $f_{cl}$. Setting $f_{cl}^{min}=1$ thus gives a maximum empirical mass-loss $\dot{M}_{max}$.
We find that for almost all stars in our sample, the clumping in the radio-emitting region is lower than in the infra-red emitting one, i.e. decreasing clumping with increasing radius. Moreover, we find that the maximum mass-loss rate is slightly lower than theoretical values for O-stars, normally included in stellar evolution models (Vink et al. 2001, A&A, 326, 295), but much lower (one order of magnitude in average) for B-stars.