Browsing by Author "Cure, M."

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    Evolution of massive stars with new hydrodynamic wind models
    (2022) Gormaz-Matamala, A. C.; Cure, M.; Meynet, G.; Cuadra, J.; Groh, J. H.; Murphy, L. J.
    Context. Mass loss through radiatively line-driven winds is central to our understanding of the evolution of massive stars in both single and multiple systems. This mass loss plays a key role in modulating massive star evolution at different metallicities, especially in the case of very massive stars (M* >= 25 M-circle dot).
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    Evolution of rotating massive stars adopting a newer, self-consistent wind prescription at Small Magellanic Cloud metallicity
    (2024) Gormaz-Matamala, A. C.; Cuadra, J.; Ekstrom, S.; Meynet, G.; Cure, M.; Belczynski, K.
    Aims. We aim to measure the impact of our mass-loss recipe in the evolution of massive stars at the metallicity of the Small Magellanic Cloud (SMC). Methods. We used the Geneva-evolution code (GENEC) to run evolutionary tracks for stellar masses ranging from 20 to 85 M-circle dot at SMC metallicity (Z(SMC) = 0.002). We upgraded the recipe for stellar winds by replacing Vink's formula with our self-consistent m-CAK prescription, which reduces the value of the mass-loss rate, (M) over dot, by a factor of between two and six depending on the mass range. Results. The impact of our new [weaker] winds is wide, and it can be divided between direct and indirect impact. For the most massive models (60 and 85 M-circle dot) with (M) over dot greater than or similar to 2 x 10(-7) M-circle dot yr(-1), the impact is direct because lower mass loss make stars remove less envelope, and therefore they remain more massive and less chemically enriched at their surface at the end of their main sequence (MS) phase. For the less massive models (20 and 25 M-circle dot) with (M) over dot less than or similar to 2 x 10(-8) M-circle dot yr(-1), the impact is indirect because lower mass loss means the stars keep high rotational velocities for a longer period of time, thus extending the H-core burning lifetime and subsequently reaching the end of the MS with higher surface enrichment. In either case, given that the conditions at the end of the H-core burning change, the stars will lose more mass during their He-core burning stages anyway. For the case of M-zams = 20-40 M-circle dot, our models predict stars will evolve through the Hertzsprung gap, from O-type supergiants to blue supergiants (BSGs), and finally red supergiants (RSGs), with larger mass fractions of helium compared to old evolution models. New models also sets the minimal initial mass required for a single star to become a Wolf-Rayet (WR) at metallicity Z = 0.002 at M-zams = 85 M-circle dot. Conclusions. These results reinforce the importance of upgrading mass-loss prescriptions in evolution models, in particular for the earlier stages of stellar lifetime, even for Z << Z(circle dot). New values for (M) over dot need to be complemented with upgrades in additional features such as convective-core overshooting and distribution of rotational velocities, besides more detailed spectroscopical observations from projects such as XShootU, in order to provide a robust framework for the study of massive stars at low-metallicity environments.
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    Evolution of rotating massive stars with new hydrodynamic wind models
    (2023) Gormaz-Matamala, A. C.; Cuadra, J.; Meynet, G.; Cure, M.
    Context. Mass loss due to radiatively line-driven winds is central to our understanding of the evolution of massive stars in both single and multiple systems. This mass loss plays a key role in modulating the stellar evolution at different metallicities, particularly in the case of massive stars with M-* >= 25 M-circle dot.
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    The wind of rotating B supergiants - II. The δ-slow hydrodynamic regime
    (2024) Venero, R. O. J.; Cure, M.; Puls, J.; Cidale, L. S.; Haucke, M.; Araya, I.; Gormaz-Matamala, A.; Arcos, C.
    The theory of line-driven winds can explain many observed spectral features in early-type stars, though our understanding the winds of B supergiants remains incomplete. The hydrodynamic equations for slowly rotating stellar winds predict two regimes based on the line-force parameter delta: the fast and the delta -slow solution. In this paper, we aim to explore the capability of the latter to explain the observed properties of B supergiant winds. We calculate H alpha line profiles, the most sensitive wind diagnostics in the optical, for both fast and delta -slow wind models. We fit them to observed data from a well-studied sample of B supergiants, by adapting the line-force parameters (k, alpha, and delta) of the hydrodynamic model. Unexpectedly, the observed H alpha spectra can be reproduced by both hydrodynamic wind regimes with similar precision. We argue that this similarity results from the similar shape of the normalized velocity law produced by both regimes in the lower, H alpha -forming wind region. Our findings raise a dichotomy, because mass-loss rates and terminal velocities (v(infinity)) for each solution are quite different. The delta -slow solution predicts maximum values for v(infinity) that are systematically lower than those measured in the ultraviolet, whereas the v(infinity) values of the fast solution are closer, and probably more appropriate. However, our results also indicate that the delta -slow solution might better describe the dense winds of B hypergiants. Multiwavelength analyses and a larger sample of stars are needed to reach a definitive conclusion.