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@article{762570, author = {Kraus, Michaela and Kubát, Jiří and Krtička, Jiří}, article_location = {Les Ulis Cedex, France}, article_number = {481}, keywords = {stars: early-type -- stars: supergiants -- stars: winds outflows -- stars: mass-loss -- stars: circumstellar matter}, language = {eng}, issn = {0004-6361}, journal = {Astronomy and Astrophysics}, title = {On the importance of the wind emission to the optical continuum of OB supergiants}, url = {http://www.aanda.org/index.php?option=article&access=standard&Itemid=129&url=/articles/aa/abs/2008/14/aa8991-07/aa8991-07.html}, volume = {36}, year = {2008} }
TY - JOUR ID - 762570 AU - Kraus, Michaela - Kubát, Jiří - Krtička, Jiří PY - 2008 TI - On the importance of the wind emission to the optical continuum of OB supergiants JF - Astronomy and Astrophysics VL - 36 IS - 481 SP - 499-506 EP - 499-506 PB - EDP Sciences SN - 00046361 KW - stars: early-type -- stars: supergiants -- stars: winds outflows -- stars: mass-loss -- stars: circumstellar matter UR - http://www.aanda.org/index.php?option=article&access=standard&Itemid=129&url=/articles/aa/abs/2008/14/aa8991-07/aa8991-07.html N2 - Context. Thermal wind emission in the form of free-free and free-bound emission is known to show up in the infrared and radio continuum of hot and massive stars. For OB supergiants with moderate mass loss rates and a wind velocity distribution with $\beta$$\simeq$ 0.8 ... 1.0, no influence of the wind to the optical continuum, i.e. for $\lambda \la$ 1.0 $\mu$m, is expected. Investigations of stellar and wind parameters of OB supergiants over the last few years suggest, however, that for many objects $\beta$ is much higher than 1.0, reaching values up to 3.5. Aims. We investigate the influence of the free-free and free-bound emission on the emerging radiation, especially at optical wavelengths, from OB supergiants having wind velocity distributions with $\beta \ge$ 1.0. Methods. For the case of a spherically symmetric, isothermal wind in local thermodynamical equilibrium (LTE) we calculate the free-free and free-bound processes and the emerging wind and total continuum spectra. We localize the generation region of the optical wind continuum and especially focus on the influence of a $\beta$-type wind velocity distribution with $\beta$ > 1 on the formation of the wind continuum at optical wavelengths. Results. The optical wind continuum is found to be generated within about 2 $R_{\rm *}$ which is exactly the wind region where $\beta$ strongly influences the density distribution. We find that for $\beta$ > 1, the continuum of a typical OB supergiant can indeed be contaminated with thermal wind emission, even at optical wavelengths. The strong increase in the optical wind emission is dominantly produced by free-bound processes. ER -
KRAUS, Michaela, Jiří KUBÁT and Jiří KRTIČKA. On the importance of the wind emission to the optical continuum of OB supergiants. \textit{Astronomy and Astrophysics}. Les Ulis Cedex, France: EDP Sciences, 2008, vol.~36, No~481, p.~499-506. ISSN~0004-6361.
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