New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars

Björklund, R.; Sundqvist, J. O.; Puls, J.; Najarro, F.

doi:10.1051/0004-6361/202038384

Cited by 104 publications

(137 citation statements)

References 60 publications

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“…We adopted v ∞ = 3.0 × v esc as in Martins & Palacios (2017) 1 . This value is consistent with both observations (Garcia et al 2014) and theoretical predictions (Björklund et al 2021) in which v ∞ /v esc is in the ranges 1.0−6.0 and 2.5−5.5, respectively. We note that the observational study of Garcia et al (2014) shows a correlation between terminal velocity and metallicity (see also Leitherer et al 1992), but no clear trend can be seen between the very scattered ratio v ∞ /v esc and metallicity.…”

Section: Evolutionary Models and Synthetic Spectrasupporting

confidence: 92%

“…In order to account for the effect of clumping in the wind (Fullerton 2011), the obtained mass-loss rates were divided by a factor of three (Cohen et al 2014). This reduction is consistent with the revision of theoretical mass-loss rates proposed by Lucy (2010), Krtička & Kubát (2017), and Björklund et al (2021).…”

Section: Evolutionary Models and Synthetic Spectrasupporting

confidence: 90%

“…We see that despite having similar spectral types, the strength of the wind features increases with initial mass. More massive stars are also more luminous and, as mass-loss rates are sensitive to luminosity (e.g., Björklund et al 2021), this translates into stronger P Cygni features. However the winds are not strong enough to cause He ii 4686 to enter the regime of giants or supergiants and the models remain classified as dwarfs.…”

Section: Metallicity Of the Small Magellanic Cloudmentioning

confidence: 99%

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Spectroscopic evolution of massive stars near the main sequence at low metallicity

Martins

2021

A&A

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Context. The evolution of massive stars is not fully understood. Several physical processes affect their life and death, with major consequences on the progenitors of core-collapse supernovae, long-soft gamma-ray bursts, and compact-object mergers leading to gravitational wave emission. Aims. In this context, our aim is to make the prediction of stellar evolution easily comparable to observations. To this end, we developed an approach called “spectroscopic evolution” in which we predict the spectral appearance of massive stars through their evolution. The final goal is to constrain the physical processes governing the evolution of the most massive stars. In particular, we want to test the effects of metallicity. Methods. Following our initial study, which focused on solar metallicity, we investigated the low Z regime. We chose two representative metallicities: 1/5 and 1/30 Z⊙. We computed single-star evolutionary tracks with the code STAREVOL for stars with initial masses between 15 and 150 M⊙. We did not include rotation, and focused on the main sequence (MS) and the earliest post-MS evolution. We subsequently computed atmosphere models and synthetic spectra along those tracks. We assigned a spectral type and luminosity class to each synthetic spectrum as if it were an observed spectrum. Results. We predict that the most massive stars all start their evolution as O2 dwarfs at sub-solar metallicities contrary to solar metallicity calculations and observations. The fraction of lifetime spent in the O2V phase increases at lower metallicity. The distribution of dwarfs and giants we predict in the SMC accurately reproduces the observations. Supergiants appear at slightly higher effective temperatures than we predict. More massive stars enter the giant and supergiant phases closer to the zero-age main sequence, but not as close as for solar metallicity. This is due to the reduced stellar winds at lower metallicity. Our models with masses higher than ∼60 M⊙ should appear as O and B stars, whereas these objects are not observed, confirming a trend reported in the recent literature. At Z = 1/30 Z⊙, dwarfs cover a wider fraction of the MS and giants and supergiants appear at lower effective temperatures than at Z = 1/5 Z⊙. The UV spectra of these low-metallicity stars have only weak P Cygni profiles. He II 1640 sometimes shows a net emission in the most massive models, with an equivalent width reaching ∼1.2 Å. For both sets of metallicities, we provide synthetic spectroscopy in the wavelength range 4500−8000 Å. This range will be covered by the instruments HARMONI and MOSAICS on the Extremely Large Telescope and will be relevant to identify hot massive stars in Local Group galaxies with low extinction. We suggest the use of the ratio of He I 7065 to He II 5412 as a diagnostic for spectral type. Using archival spectroscopic data and our synthetic spectroscopy, we show that this ratio does not depend on metallicity. Finally, we discuss the ionizing fluxes of our models. The relation between the hydrogen ionizing flux per unit area versus effective temperature depends only weakly on metallicity. The ratios of He I and He II to H ionizing fluxes both depend on metallicity, although in a slightly different way. Conclusions. We make our synthetic spectra and spectral energy distributions available to the community.

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Section: Evolutionary Models and Synthetic Spectrasupporting

confidence: 92%

Section: Evolutionary Models and Synthetic Spectrasupporting

confidence: 90%

Section: Metallicity Of the Small Magellanic Cloudmentioning

confidence: 99%

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Spectroscopic evolution of massive stars near the main sequence at low metallicity

Martins

2021

A&A

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“…These variations are not captured in rapid population synthesis codes, in particular those reliant on the fits to single star evolution of Hurley et al (2000) which are based on detailed stellar models without mass loss and with a fixed amount of overshooting. Stellar winds may be overestimated in our calculations (Björklund et al 2021), while observations of massive stars suggest that our choice for overshooting from a convective hydrogen-burning core is underestimated for stars with masses >15 M (Castro et al 2014). Keeping in mind that due to uncertainties in stellar evolution, a halted expansion in the HG is uncertain, we can still study what would be the consequences in the evolution of a star if this effect is real.…”

Section: Resultsmentioning

confidence: 91%

The role of mass transfer and common envelope evolution in the formation of merging binary black holes

Marchant

Pappas

Gallegos-Garcia

et al. 2021

A&A

110

117

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As the number of merging binary black holes observed with ground-based gravitational-wave detectors grows, increasingly accurate theoretical models are required to compare them to the observed sample and disentangle contributions from multiple channels. In formation models involving isolated binary stars, important uncertainties remain regarding the stability of mass transfer and common-envelope evolution. To study some of these uncertainties, we have computed binary simulations using the MESA code consisting of a 30 M⊙ star in a low metallicity (Z⊙/10) environment with a black-hole companion. We have developed an updated prescription to compute mass transfer rates including the possibility of outflows from outer Lagrangian points, as well as a method to self-consistently determine the core-envelope boundary in cases where there is common-envelope evolution. We find that binaries survive common-envelope evolution only if unstable mass transfer happens after the formation of a deep convective envelope, resulting in a narrow range (0.2 dex) in period for successful envelope ejection. All cases where binary interaction is initiated with a radiative envelope have large binding energies (∼1050 erg), and they result in mergers during the common-envelope phase even under the assumption that all the internal and recombination energy of the envelope, as well as the energy from an inspiral, is used to eject the envelope. This is independent of whether or not helium is ignited in the core of the donor, conditions under which various rapid-population synthesis calculations assume a successful envelope ejection is possible. Moreover, we find that the critical mass ratio for instability is such that across a large range in initial orbital periods (∼1−1000 days), merging binary black holes can be formed via stable mass transfer. A large fraction of these systems undergo overflow of their L2 equipotential, in which case we find that stable mass transfer produces merging binary black holes even under extreme assumptions of mass and angular momentum outflows. Our conclusions are limited to the study of one donor mass at a single metallicity, but they suggest that population synthesis calculations overestimate the formation rate of merging binary black holes produced by common-envelope evolution and that stable mass transfer could dominate the formation rate from isolated binaries. This is in agreement with a few other recent studies. Further work is required to extend these results to different masses and metallicities as well as to understand how they can be incorporated into rapid population synthesis calculations.

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“…Dedicated simulations of the winds of hot stars are now coming with results that are much more in agreement with the observations (Sundqvist et al, 2019;Björklund et al, 2020). They need to be implemented in stellar evolution codes so that we can assess the changes they bring to the outcomes of stellar modeling.…”

Section: Discussion and Perspectivesmentioning

confidence: 87%

Massive Star Modeling and Nucleosynthesis

Ekström

2021

Front. Astron. Space Sci.

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After a brief introduction to stellar modeling, the main lines of massive star evolution are reviewed, with a focus on the nuclear reactions from which the star gets the needed energy to counterbalance its gravity. The different burning phases are described, as well as the structural impact they have on the star. Some general effects on stellar evolution of uncertainties in the reaction rates are presented, with more precise examples taken from the uncertainties of the 12C(α, γ)16O reaction and the sensitivity of the s-process on many rates. The changes in the evolution of massive stars brought by low or zero metallicity are reviewed. The impact of convection, rotation, mass loss, and binarity on massive star evolution is reviewed, with a focus on the effect they have on the global nucleosynthetic products of the stars.

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New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars

Cited by 104 publications

References 60 publications

Spectroscopic evolution of massive stars near the main sequence at low metallicity

Spectroscopic evolution of massive stars near the main sequence at low metallicity

The role of mass transfer and common envelope evolution in the formation of merging binary black holes

Massive Star Modeling and Nucleosynthesis

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