Hot subdwarf wind models with accurate abundances I. Hydrogen dominated stars HD 49798 and BD+18 degrees 2647

KRTIČKA, Jiří, Jan JANÍK, Iva KRTIČKOVÁ, S. MEREGHETTI, F. PINTORE, P. NEMETH, Jiří KUBÁT and M. VUCKOVIC. Hot subdwarf wind models with accurate abundances I. Hydrogen dominated stars HD 49798 and BD+18 degrees 2647. ASTRONOMY & ASTROPHYSICS. LES ULIS CEDEX A: EDP SCIENCES S A, 2019, vol. 631, OCT 22 2019, p. 1-11. ISSN 0004-6361. Available from: https://dx.doi.org/10.1051/0004-6361/201936208.

Basic information

• Original name: Hot subdwarf wind models with accurate abundances I. Hydrogen dominated stars HD 49798 and BD+18 degrees 2647
• Authors: KRTIČKA, Jiří (203 Czech Republic, guarantor, belonging to the institution), Jan JANÍK (203 Czech Republic, belonging to the institution), Iva KRTIČKOVÁ (203 Czech Republic, belonging to the institution), S. MEREGHETTI (380 Italy), F. PINTORE (380 Italy), P. NEMETH (348 Hungary), Jiří KUBÁT (203 Czech Republic) and M. VUCKOVIC (191 Croatia).
• Edition: ASTRONOMY & ASTROPHYSICS, LES ULIS CEDEX A, EDP SCIENCES S A, 2019, 0004-6361.

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: 5.636
• RIV identification code: RIV/00216224:14310/19:00108216
• Organization unit: Faculty of Science
• Doi: http://dx.doi.org/10.1051/0004-6361/201936208
• UT WoS: 000515090700003
• Keywords in English: stars: winds; outflows stars; mass-loss; stars: early-type; subdwarfs; X-rays: binaries
• Tags: rivok
• Tags: International impact, Reviewed

Abstract

Context. Hot subdwarfs are helium burning objects in late stages of their evolution. These subluminous stars can develop winds driven by light absorption in the lines of heavier elements. The wind strength depends on chemical composition which can significantly vary from star to star. Aims. We aim to understand the influence of metallicity on the strength of the winds of the hot hydrogen-rich subdwarfs HD 49798 and BD+18 2647. Methods. We used high -resolution UV and optical spectra to derive stellar parameters and abundances using the TLUSTY and SYNSPEC codes. For derived stellar parameters, we predicted wind structure (including mass -loss rates and terminal velocities) with our METUJE code. Results. We derived effective temperature Teff = 45 900 K and mass M = 1.46 M for HD 49798 and Teff = 73 000 K and M = 0.38 M for BD+18 2647. The derived surface abundances can be interpreted as a result of interplay between stellar evolution and diffusion. The subdwarf HD 49798 has a strong wind that does not allow for chemical separation and consequently the star shows solar chemical composition modified by hydrogen burning. On the other hand, we did not find any wind in BD+18 2647 and its abundances are therefore most likely affected by radiative diffusion. Accurate abundances do not lead to a significant modification of wind mass -loss rate for HD 49798, because the increase of the contribution of iron and nickel to the radiative force is compensated by the decrease of the radiative force due to other elements. The resulting wind mass -loss rate M = 2.1 x 10-9 M. yr1 predicts an X-ray light curve during the eclipse which closely agrees with observations. On the other hand, the absence of the wind in BD+18 2647 for accurate abundances is a result of its peculiar chemical composition. Conclusions. Wind models with accurate abundances provide more reliable wind parameters, but the influence of abundances on the wind parameters is limited in many cases.

Links

• GA18-05665S, research and development project: Name: Ztráta hmoty v pozdních fázích vývoje hmotných hvězd

Investor: Czech Science Foundation