X-Shooting ULLYSES: Massive stars at low metallicity

Context . Mass loss governs the evolution of massive stars and shapes the stellar surroundings. To quantify the impact of the stellar winds, we need to know the exact mass-loss rates; however, empirical constraints on the rates are hampered by limited knowledge of their small-scale wind structure, also referred to as ‘wind clumping’. Aims . We aim to improve empirical constraints on the mass loss of massive stars by investigating the clumping properties of their winds, in particular, the relation between stellar parameters and wind structure. Methods . We analysed the optical and ultraviolet spectra of 25 O-type giants and supergiants in the Large Magellanic Cloud, using the model atmosphere code FASTWIND and a genetic algorithm. We derived the stellar and wind parameters, including detailed clumping properties, such as the amount of clumping, the density of the interclump medium, velocity–porosity of the medium, and wind turbulence. Results . We obtained stellar and wind parameters for 24 of our sample stars and found that the winds are highly clumped, with an average clumping factor of 〈 f cl 〉 = 33 14, an interclump density factor of 〈 f ic 〉 = 0.2 0.1, and moderate-to-strong velocity-porosity effects of 〈 f vel 〉 = 0.6 0.2. The scatter around the average values of the wind-structure parameters is large. With the exception of a significant, positive correlation between the interclump density factor and mass loss, we find no dependence of clumping parameters on the mass-loss rate or stellar properties. Conclusions . In the luminosity range we investigate here, the empirical and theoretical mass-loss rates both have a scatter of about 0.5 dex (or a factor 3). Within this uncertainty, the empirical rates and theoretical predictions are in agreement. The origin of the scatter of the empirically inferred mass-loss rates requires further investigation. It is possible that our description of wind clumping is still not sufficient to capture effects of the structured wind, which could contribute to the scatter.

Authors

Institutions

Publication Details

Journal
Astronomy and Astrophysics
Published
2025-04-01
DOI
https://doi.org/10.1051/0004-6361/202452784
Citations
5
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
5.77

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

X-Shooting ULLYSES: Massive stars at low metallicity

F. Backs, J. O. Sundqvist, L. Mahy, P. A. Crowther et al.
5 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
5.77
article

X-Shooting ULLYSES: Massive stars at low metallicity

F. Backs, J. O. Sundqvist, L. Mahy, P. A. Crowther, Christiana Erba, S. A. Brands, J. Puls, H. Sana, R. K. Prinja, Alex de Koter, F. A. Driessen, J. S. Vink, F. Najarro, A. Herrero, R. R. Lefever, Calum Hawcroft, Lex Kaper, F. Tramper, J. M. Bestenlehner, Richard Ignace, V. Ramachandran, A. A. C. Sander, N. D. Kee, D. J. Hillier
article en
5 citations

Abstract

Context . Mass loss governs the evolution of massive stars and shapes the stellar surroundings. To quantify the impact of the stellar winds, we need to know the exact mass-loss rates; however, empirical constraints on the rates are hampered by limited knowledge of their small-scale wind structure, also referred to as ‘wind clumping’. Aims . We aim to improve empirical constraints on the mass loss of massive stars by investigating the clumping properties of their winds, in particular, the relation between stellar parameters and wind structure. Methods . We analysed the optical and ultraviolet spectra of 25 O-type giants and supergiants in the Large Magellanic Cloud, using the model atmosphere code FASTWIND and a genetic algorithm. We derived the stellar and wind parameters, including detailed clumping properties, such as the amount of clumping, the density of the interclump medium, velocity–porosity of the medium, and wind turbulence. Results . We obtained stellar and wind parameters for 24 of our sample stars and found that the winds are highly clumped, with an average clumping factor of 〈 f cl 〉 = 33 14, an interclump density factor of 〈 f ic 〉 = 0.2 0.1, and moderate-to-strong velocity-porosity effects of 〈 f vel 〉 = 0.6 0.2. The scatter around the average values of the wind-structure parameters is large. With the exception of a significant, positive correlation between the interclump density factor and mass loss, we find no dependence of clumping parameters on the mass-loss rate or stellar properties. Conclusions . In the luminosity range we investigate here, the empirical and theoretical mass-loss rates both have a scatter of about 0.5 dex (or a factor 3). Within this uncertainty, the empirical rates and theoretical predictions are in agreement. The origin of the scatter of the empirically inferred mass-loss rates requires further investigation. It is possible that our description of wind clumping is still not sufficient to capture effects of the structured wind, which could contribute to the scatter.

Astronomy and AstrophysicsVol. 697
East Tennessee State University (US), Space Telescope Science Institute (US), Goddard Space Flight Center (US), Universidad de La Laguna (ES), Université du Québec à Montréal (CA), University of Pittsburgh (US), Heidelberg University (DE), Royal Observatory of Belgium (BE), Armagh Observatory & Planetarium (GB), Czech Academy of Sciences, Astronomical Institute (CZ), LMU Klinikum (DE), Université Bourgogne Franche-Comté (FR), Centro de Astrobiología (ES), Instituto de Astrofísica de Canarias (ES), University College London (GB), Université de Montréal (CA), Ludwig-Maximilians-Universität München (DE), University of Amsterdam (NL), University of Sheffield (GB), KU Leuven (BE)
National Aeronautics and Space Administration, Space Telescope Science Institute, Deutsche Forschungsgemeinschaft, Grantová Agentura České Republiky, Bundesministerium für Bildung und Forschung, Fonds Wetenschappelijk Onderzoek, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg, Ministerio de Ciencia e Innovación, Vlaamse regering, Nederlandse Onderzoekschool Voor Astronomie, HORIZON EUROPE Framework Programme, Science and Technology Facilities Council, European Research Council, Agencia Estatal de Investigación
Openalex Percentile: Top 5%
Stellar, planetary, and galactic studies
5.77
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.