Global hot-star wind models for stars from Magellanic Clouds

KRTIČKA, Jiří and Jiří KUBÁT. Global hot-star wind models for stars from Magellanic Clouds. Astronomy and Astrophysics. EDP Sciences, 2018, vol. 612, duben, p. "A20-1"-"A20-11", 11 pp. ISSN 1432-0746. Available from: https://dx.doi.org/10.1051/0004-6361/201731969.

Basic information

• Original name: Global hot-star wind models for stars from Magellanic Clouds
• Name in Czech: Globální modely větru horkých hvězd z Magellanových mračen
• Authors: KRTIČKA, Jiří (203 Czech Republic, guarantor, belonging to the institution) and Jiří KUBÁT (203 Czech Republic).
• Edition: Astronomy and Astrophysics, EDP Sciences, 2018, 1432-0746.

Other information

• Original language: English
• Type of outcome: Article in a journal
• Field of Study: 10308 Astronomy
• Country of publisher: France
• Confidentiality degree: is not subject to a state or trade secret
• WWW: URL
• Impact factor: Impact factor: 6.209
• RIV identification code: RIV/00216224:14310/18:00100896
• Organization unit: Faculty of Science
• Doi: http://dx.doi.org/10.1051/0004-6361/201731969
• UT WoS: 000430139600001
• Keywords in English: stars: winds outflows; stars: mass-loss; stars: early-type; Magellanic Clouds; hydrodynamics; radiative transfer
• Tags: International impact, Reviewed

Abstract

We provide mass-loss rate predictions for O stars from Large and Small Magellanic Clouds. We calculate global (unified, hydrodynamic) model atmospheres of main sequence, giant, and supergiant stars for chemical composition corresponding to Magellanic Clouds. The models solve radiative transfer equation in comoving frame, kinetic equilibrium equations (also known as NLTE equations), and hydrodynamical equations from (quasi-)hydrostatic atmosphere to expanding stellar wind. The models allow us to predict wind density, velocity, and temperature (consequently also the terminal wind velocity and the mass-loss rate) just from basic global stellar parameters. As a result of their lower metallicity, the line radiative driving is weaker leading to lower wind mass-loss rates with respect to the Galactic stars. We provide a formula that fits the mass-loss rate predicted by our models as a function of stellar luminosity and metallicity. On average, the mass-loss rate scales with metallicity as dMdt sim Z^0.59. The predicted mass-loss rates are lower than mass-loss rates derived from Halpha diagnostics and can be reconciled with observational results assuming clumping factor Cc = 9. On the other hand, the predicted mass-loss rates either agree or are slightly higher than the mass-loss rates derived from ultraviolet wind line profiles. The calculated P v ionization fractions also agree with values derived from observations for LMC stars with Teff < 40 000 K. Taken together, our theoretical predictions provide reasonable models with consistent mass-loss rate determination, which can be used for quantitative study of stars from Magellanic Clouds.

Abstract (in Czech)

Počítáme rychlost ztráty hvězd typu O z Velkého a Malého Magellanova mračna. Modely předpovídají hustotu, rychlost a teplotu větru. V důsledku menšího obsahu těžších prvků je rychlost ztráty hmoty menší než hvězd z naší Galaxie. Předpovězená rychlost ztráty hmoty souhlasí s hodnotami odvozenými z pozorování síly čáry Halfa za předpokladu, že faktor nehomogenity je roven alespoň 9. Na druhou stranu předpovědi dobře souhlasí s výsledky získanými z ultrafialové oblasti.

Links

• GA13-10589S, research and development project: Name: Ztráta hmoty horkých hmotných hvězd

Investor: Czech Science Foundation