Hot subdwarf wind models with accurate abundances II.
Helium-dominated merger products CD-46 8926 and CD-51 11879

J 2024

Hot subdwarf wind models with accurate abundances II. Helium-dominated merger products CD-46 8926 and CD-51 11879

KRTIČKA, Jiří, Iva KRTIČKOVÁ, Jan JANÍK, P. NÉMETH, J. KUBÁT et. al.

Basic information

Original name

Hot subdwarf wind models with accurate abundances II. Helium-dominated merger products CD-46 8926 and CD-51 11879

Authors

KRTIČKA, Jiří (203 Czech Republic, belonging to the institution), Iva KRTIČKOVÁ (203 Czech Republic, belonging to the institution), Jan JANÍK (203 Czech Republic, belonging to the institution), P. NÉMETH, J. KUBÁT and M. VUČKOVIĆ

Edition

Astronomy and Astrophysics, EDP Sciences, 2024, 0004-6361

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10308 Astronomy

Country of publisher

France

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

URL

Impact factor

Impact factor: 6.500 in 2022

Organization unit

Faculty of Science

DOI

http://dx.doi.org/10.1051/0004-6361/202347978

UT WoS

001181364400009

Keywords in English

stars: winds; outflows; stars: mass-loss; stars: early-type; stars: abundances; subdwarfs

Abstract

V originále

Context. Helium-dominated subdwarfs are core helium burning stars stripped of their envelope. The nuclear evolution of these stars alters surface abundances. Modified abundances impact the strength of the stellar wind. Aims. We aim to understand the influence of modified surface abundances on the strength of the stellar wind in the helium-dominated subdwarfs CD–46 8926 and CD–51 11879. A modified wind strength could resolve the problem with the X-ray emission of these stars, as the expected X-ray luminosity of both stars is significantly higher than the upper limit determined from observations. Methods. We used our own optical spectroscopy combined with archival ultraviolet spectroscopy and photometry to derive basic parameters and surface abundances of selected subdwarfs. The resulting parameterst served as input for the METUJE stellar wind code, which predicts the wind structure of these stars. We compared the derived wind parameters with the predictions derived for solar abundances. Results. The optical analysis showed that both subdwarfs have effective temperatures in excess of 60 kK and a strong overabundance of carbon in the case of CD–46 8926 and nitrogen in the case of CD–51 11879. We interpret the abundance patterns as being a result of enrichment by the products of nuclear reactions. The modified abundances reduce the wind mass-loss rate by tens of percent. The reduction improves the predicted wind line profiles in comparison to observations. The change in helium abundance does not have a strong effect on the wind parameters. As a result of a lower estimated bolometric luminosity and mass-loss rate and a larger distance, the expected X-ray luminosities become lower and agree with observational upper limits. Conclusions. The nucleosynthesis does not significantly alter the strength of the wind of hot subdwarfs, but the inclusion of proper stellar parameters improves the agreement with observational wind characteristics. Our analysis indicates that subdwarfs overabundant in helium are typically able to launch wind. This conclusion is supported by data gathered for thousands of subdwarfs from the literature, which shows that subdwarfs overabundant in helium avoid the region in the Kiel diagram where the winds are predicted to be absent. This can be interpreted in terms of the gravitational settling of helium, which is suppressed by the winds.

Links

90254, large research infrastructures

Name: e-INFRA CZ II

Citovat

KRTIČKA, Jiří, Iva KRTIČKOVÁ, Jan JANÍK, P. NÉMETH, J. KUBÁT and M. VUČKOVIĆ. Hot subdwarf wind models with accurate abundances II. Helium-dominated merger products CD-46 8926 and CD-51 11879. Astronomy and Astrophysics. EDP Sciences, 2024, vol. 683, March 2024, p. 1-10. ISSN 0004-6361. Available from: https://dx.doi.org/10.1051/0004-6361/202347978.

@article{2396860,
   author = {Krtička, Jiří and Krtičková, Iva and Janík, Jan and Németh, P. and Kubát, J. and Vučković, M.},
   article_number = {March 2024},
   doi = {http://dx.doi.org/10.1051/0004-6361/202347978},
   keywords = {stars: winds; outflows; stars: mass-loss; stars: early-type; stars: abundances; subdwarfs},
   language = {eng},
   issn = {0004-6361},
   journal = {Astronomy and Astrophysics},
   title = {Hot subdwarf wind models with accurate abundances II. Helium-dominated merger products CD-46 8926 and CD-51 11879},
   url = {https://www.aanda.org/articles/aa/full_html/2024/03/aa47978-23/aa47978-23.html},
   volume = {683},
   year = {2024}
}

TY  - JOUR
ID  - 2396860
AU  - Krtička, Jiří - Krtičková, Iva - Janík, Jan - Németh, P. - Kubát, J. - Vučković, M.
PY  - 2024
TI  - Hot subdwarf wind models with accurate abundances II. Helium-dominated merger products CD-46 8926 and CD-51 11879
JF  - Astronomy and Astrophysics
VL  - 683
IS  - March 2024
SP  - 1-10
EP  - 1-10
PB  - EDP Sciences
SN  - 00046361
KW  - stars: winds
KW  - outflows
KW  - stars: mass-loss
KW  - stars: early-type
KW  - stars: abundances
KW  - subdwarfs
UR  - https://www.aanda.org/articles/aa/full_html/2024/03/aa47978-23/aa47978-23.html
N2  - Context. Helium-dominated subdwarfs are core helium burning stars stripped of their envelope. The nuclear evolution of these stars alters surface abundances. Modified abundances impact the strength of the stellar wind. Aims. We aim to understand the influence of modified surface abundances on the strength of the stellar wind in the helium-dominated subdwarfs CD–46 8926 and CD–51 11879. A modified wind strength could resolve the problem with the X-ray emission of these stars, as the expected X-ray luminosity of both stars is significantly higher than the upper limit determined from observations. Methods. We used our own optical spectroscopy combined with archival ultraviolet spectroscopy and photometry to derive basic parameters and surface abundances of selected subdwarfs. The resulting parameterst served as input for the METUJE stellar wind code, which predicts the wind structure of these stars. We compared the derived wind parameters with the predictions derived for solar abundances. Results. The optical analysis showed that both subdwarfs have effective temperatures in excess of 60 kK and a strong overabundance of carbon in the case of CD–46 8926 and nitrogen in the case of CD–51 11879. We interpret the abundance patterns as being a result of enrichment by the products of nuclear reactions. The modified abundances reduce the wind mass-loss rate by tens of percent. The reduction improves the predicted wind line profiles in comparison to observations. The change in helium abundance does not have a strong effect on the wind parameters. As a result of a lower estimated bolometric luminosity and mass-loss rate and a larger distance, the expected X-ray luminosities become lower and agree with observational upper limits. Conclusions. The nucleosynthesis does not significantly alter the strength of the wind of hot subdwarfs, but the inclusion of proper stellar parameters improves the agreement with observational wind characteristics. Our analysis indicates that subdwarfs overabundant in helium are typically able to launch wind. This conclusion is supported by data gathered for thousands of subdwarfs from the literature, which shows that subdwarfs overabundant in helium avoid the region in the Kiel diagram where the winds are predicted to be absent. This can be interpreted in terms of the gravitational settling of helium, which is suppressed by the winds.
ER  -

KRTIČKA, Jiří, Iva KRTIČKOVÁ, Jan JANÍK, P. NÉMETH, J. KUBÁT and M. VUČKOVI$\backslash$'C. Hot subdwarf wind models with accurate abundances II. Helium-dominated merger products CD-46 8926 and CD-51 11879. \textit{Astronomy and Astrophysics}. EDP Sciences, 2024, vol.~683, March 2024, p.~1-10. ISSN~0004-6361. Available from: https://dx.doi.org/10.1051/0004-6361/202347978.

Detailed Information on Publication Record