On the importance of the wind emission to the optical continuum
of OB supergiants

KRAUS, Michaela, Jiří KUBÁT a Jiří KRTIČKA. On the importance of the wind emission to the optical continuum of OB supergiants. Astronomy and Astrophysics. Les Ulis Cedex, France: EDP Sciences, 2008, roč. 36, č. 481, s. 499-506. ISSN 0004-6361.

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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  -

Základní údaje
Originální název	On the importance of the wind emission to the optical continuum of OB supergiants
Název česky	O důležitosti emise větru pro optické kontinuum OB veleobrů
Autoři	KRAUS, Michaela (276 Německo), Jiří KUBÁT (203 Česká republika) a Jiří KRTIČKA (203 Česká republika, garant, domácí).
Vydání	Astronomy and Astrophysics, Les Ulis Cedex, France, EDP Sciences, 2008, 0004-6361.

Další údaje
Originální jazyk	angličtina
Typ výsledku	Článek v odborném periodiku
Obor	10308 Astronomy
Stát vydavatele	Francie
Utajení	není předmětem státního či obchodního tajemství
WWW	URL
Impakt faktor	Impact factor: 4.153
Kód RIV	RIV/00216224:14310/08:00040362
Organizační jednotka	Přírodovědecká fakulta
UT WoS	000254515800025
Klíčová slova anglicky	stars: early-type -- stars: supergiants -- stars: winds outflows -- stars: mass-loss -- stars: circumstellar matter
Příznaky	Mezinárodní význam, Recenzováno
Změnil	Změnil: prof. Mgr. Jiří Krtička, Ph.D., učo 8714. Změněno: 30. 4. 2011 17:02.

Anotace

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.

Anotace česky
Ukázali jsme, že optické kontinuum OB veleobrů vzniká ve vzdálenosti menší než 2 R_* od hvězdy. Pro pomalu urychlované větry podstatná část kontinua vzniká ve hvězdném větru.

Návaznosti
KJB300030701, projekt VaV	Název: B[e] veleobři: kde je jejich místo ve vývoji velmi hmotných hvězd?

VytisknoutZobrazeno: 26. 4. 2024 08:46

On the importance of the wind emission to the optical continuum of OB supergiants

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