NLTE models of line-driven stellar winds II. O stars in the Small Magellanic Cloud

KRTIČKA, Jiří. NLTE models of line-driven stellar winds II. O stars in the Small Magellanic Cloud. Monthly Notices of the Royal Astronomical Society. 2006, vol. 367, No 3, p. 1282-1296. ISSN 0035-8711.

Basic information

• Original name: NLTE models of line-driven stellar winds II. O stars in the Small Magellanic Cloud
• Name in Czech: NLTE modely hvězdného větru - II. O hvězdy v Malém Magellanově mračnu
• Authors: KRTIČKA, Jiří (203 Czech Republic, guarantor).
• Edition: Monthly Notices of the Royal Astronomical Society, 2006, 0035-8711.

Other information

• Original language: English
• Type of outcome: Article in a journal
• Field of Study: 10308 Astronomy
• Country of publisher: United Kingdom of Great Britain and Northern Ireland
• Confidentiality degree: is not subject to a state or trade secret
• WWW: URL
• Impact factor: Impact factor: 5.057
• RIV identification code: RIV/00216224:14310/06:00015648
• Organization unit: Faculty of Science
• UT WoS: 000236385600039
• Keywords in English: instabilities hydrodynamics stars: early-type stars: mass-loss stars: winds; outflows Magellanic Clouds
• Tags: outflows Magellanic Clouds
• Tags: International impact, Reviewed

Abstract

We calculate non-local thermodynamic equilibrium (NLTE) line-driven wind models of selected O stars in the spectral range of O4 to O9 in the Small Magellanic Cloud (SMC). We compare predicted basic wind properties, i.e. the terminal velocity and the mass-loss rate with values derived from observation. We found relatively good agreement between theoretical and observed terminal velocities. On the other hand, predicted mass-loss rates and mass-loss rates derived from observation are in a good agreement only for higher mass-loss rates. Theoretical mass-loss rates lower than approximately 10^-7 M yr^-1 are significantly higher than those derived from observation. These results confirm the previously reported problem of weak winds, since our calculated mass-loss rates are in fair agreement with predictions of Vink et al. We study multicomponent models for these winds. For this purpose we develop a more detailed description of wind decoupling. We show that the instability connected with the decoupling of individual wind elements may occur for low-density winds. In the case of winds with very low observed mass-loss rates the multicomponent effects are important for the wind structure, however this is not able to explain consistently the difference between the predicted mass-loss rate and the mass-loss rate derived from observation for these stars. Similar to previous studies, we found the level of dependence of the wind parameters on the metallicity. We conclude that the wind mass-loss rate significantly increases with metallicity as , whereas the terminal velocity of wind on average depends on metallicity only slightly, namely v~Z^0.06 (for studied stars).

Abstract (in Czech)

Byly spočteny NLTE modely hvězdného větru vybraných O hvězd z Malého Magellanova mračna. Porovnáváme předpovězenou konečnou rychlost větru a rychlost ztráty hmoty s hodnotami získanými z pozorování. Byl nalezen poměrně dobrý soulad mezi předpovězenými a pozorovanými konečnými rychlostmi větru. Předpovězené a pozorované rychlosti ztráty hmoty jsou ale v souladu pouze pro hvězdy s vysokou rychlostí ztráty hmoty. Pro hvězdy s rychlostí ztráty hmoty menší než asi 10^-7 M yr^-1 jsou předpovězené rychlosti ztráty hmoty podstatně vyšší než pozorované. Tyto výpočty potvrzují nedávno nalezený problém hvězd s malou rychlostí ztráty hmoty. Byly studovány vícesložkové modely větru hvězd s malou hustotou a bylo ukázáno, že pro mnohé větry hvězd jsou vícesložkové jevy důležité. Byl studován vliv chemického složení na konečnou rychlost hvězdného větru a na rychlost ztráty hmoty.

Links

• GP205/03/D020, research and development project: Name: Hydrodynamika hvězdného větru horkých hvězd

Investor: Czech Science Foundation, Hydrodynamics of stellar wind of hot stars