Grids of stellar models with rotation

Groh, J. H.; Ekström, Sylvia; Georgy, Cyril; Meynet, Georges; Choplin, Arthur; Eggenberger, P.; Hirschi, Raphaël; Maeder, A.; Murphy, Laura Bennett; Boian, Ioana; Farrell, Eoin

doi:10.1051/0004-6361/201833720

Cited by 88 publications

(81 citation statements)

References 111 publications

(140 reference statements)

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“…It would appear naively that the fraction of WR stars forming through binary mass-transfer should grow with decreasing metallicity. Indeed, this expectation is repeatedly claimed in the literature (e.g., Maeder & Meynet 1994;Bartzakos et al 2001;Smith 2014;Groh et al 2019).…”

Section: Introductionmentioning

confidence: 56%

Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity

Shenar

Gilkis

Vink

et al. 2020

A&A

103

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Context. Classical Wolf-Rayet (WR) stars are massive, hydrogen depleted, post main-sequence stars that exhibit emission-line dominated spectra. For a given metallicity Z, stars exceeding a certain initial mass M WR single (Z) can reach the WR phase through intrinsic mass-loss or eruptions (single-star channel). In principle, stars of lower masses can reach the WR phase via stripping through binary interactions (binary channel). Because winds become weaker at low Z, it is commonly assumed that the binary channel dominates the formation of WR stars in environments with low metallicity such as the Small and Large Magellanic Clouds (SMC, LMC). However, the reported WR binary fractions of 30 − 40% in the SMC (Z = 0.002) and LMC (Z = 0.006) are comparable to that of the Galaxy (Z = 0.014), and no evidence for the dominance of the binary channel at low Z could be identified observationally. Here, we explain this apparent contradiction by considering the minimum initial mass M WR spec (Z) needed for the stripped product to appear as a WR star. Aims. By constraining M WR spec (Z) and M WR single (Z), we estimate the importance of binaries in forming WR stars as a function of Z. Methods. We calibrate M WR spec (Z) using the lowest-luminosity WR stars in the Magellanic Clouds and the Galaxy. A range of M WR single values are explored using various evolution codes. We estimate the additional contribution of the binary channel by considering the interval [M WR spec (Z), M WR single (Z)], which characterizes the initial-mass range in which the binary channel can form additional WR stars. Results. The WR-phenomenon ceases below luminosities of log L≈4. 9, 5.25, and 5.6 [L ] in the Galaxy, the LMC, and the SMC, respectively, which translates to minimum He-star masses of 7.5, 11, 17 M and minimum initial masses of M WR spec = 18, 23, 37 M . Stripped stars with lower initial masses in the respective galaxies would tend to not appear as WR stars. The minimum mass necessary for self-stripping, M WR single (Z), is strongly model dependent, but lies in the range 20 − 30, 30 − 60, and 40 M for the Galaxy, LMC, and SMC, respectively. We find that that the additional contribution of the binary channel is a non-trivial and model-dependent function of Z that cannot be conclusively claimed to be monotonically increasing with decreasing Z. Conclusions. The WR spectral appearance arises from the presence of strong winds. Therefore, both M WR spec and M WR single increase with decreasing metallicity. Considering this, we show that one should not a-priori expect that binary interactions become increasingly important in forming WR stars at low Z, or that the WR binary fraction grows with decreasing Z.

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Section: Introductionmentioning

confidence: 56%

Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity

Shenar

Gilkis

Vink

et al. 2020

A&A

103

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“…The reasons can either be observational (very fast evolving to the RSG phase) or evolutionary (the upper limit of the initial mass of the RSGs phase decreases at low metallicities). The expected initial mass range of the RSG phase becomes smaller, that is, Groh et al 2019). In this context, a similar work to establish the census and physical properties of blue supergiants in these galaxies is required.…”

Section: Discussionmentioning

confidence: 99%

Physical parameters of red supergiants in dwarf irregular galaxies in the Local Group

Britavskiy

Bonanos

Herrero

et al. 2019

A&A

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Context. Increasing the statistics of evolved massive stars in the Local Group enables investigating their evolution at different metallicities. During the late stages of stellar evolution, the physics of some phenomena, such as episodic and systematic mass loss, are not well constrained. For example, the physical properties of red supergiants (RSGs) in different metallicity regimes remain poorly understood. Thus, we initiated a systematic study of RSGs in dwarf irregular galaxies (dIrrs) in the Local Group. Aims. We aim to derive the fundamental physical parameters of RSGs and characterize the RSG population in nearby dIrrs. Methods. The target selection is based on 3.6 µm and 4.5 µm photometry from archival Spitzer Space Telescope images of nearby galaxies. We selected 46 targets in the dIrrs IC 10, IC 1613, Sextans B, and the Wolf-Lundmark-Melotte (WLM) galaxy that we observed with the GTC-OSIRIS and VLT-FORS2 instruments. We used several photometric techniques together with a spectral energy distribution analysis to derive the luminosities and effective temperatures of known and newly discovered RSGs. Results. We identified and spectroscopically confirmed 4 new RSGs, 5 previously known RSGs, and 5 massive asymptotic giant branch (AGB) stars. We added known objects from previous observations. In total, we present spectral classification and fundamental physical parameters of 25 late-type massive stars in the following dIrrs: Sextans A, Sextans B, IC 10, IC 1613, Pegasus, Phoenix, and WLM. This includes 17 RSGs and 8 AGB stars that have been identified here and previously. Conclusions. Based on our observational results and PARSEC evolutionary models, we draw the following conclusions: (i) a trend to higher minimum effective temperatures at lower metallicities and (ii) the maximum luminosity of RSGs appears to be constant at log(L/L ) ≈ 5.5, independent of the metallicity of the host environment (up to [Fe/H] ≈ −1 dex).

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“…Differential rotation can induce such mixing. Evolution models for rotating massive stars have become widely available [62][63][64][65]. A comparison of models for rotating and non-rotating stars is presented in Figure 14.…”

Section: Stellar Evolutionmentioning

confidence: 99%

Massive Star Formation in the Ultraviolet Observed with the Hubble Space Telescope

Leitherer

2020

Galaxies

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Spectroscopic observations of a massive star formation in the ultraviolet and their interpretation are reviewed. After a brief historical retrospective, two well-studied resolved star clusters and the surrounding H II regions are introduced: NGC 2070 in the Large Magellanic Cloud and NGC 604 in M33. These regions serve as a training set for studies of more distant clusters, which can no longer be resolved into individual stars. Observations of recently formed star clusters and extended regions in star-forming galaxies in the nearby universe beyond the Local Group are presented. Their interpretation relies on spectral synthesis models. The successes and failures of such models are discussed, and future directions are highlighted. I present a case study of the extraordinary star cluster and giant H II region in the blue compact galaxy II Zw 40. The review concludes with a preview of two upcoming Hubble Space Telescope programs: ULLYSES, a survey of massive stars in nearby galaxies, and CLASSY, a study of massive star clusters in star-forming galaxies.

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Grids of stellar models with rotation

Cited by 88 publications

References 111 publications

Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity

Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity

Physical parameters of red supergiants in dwarf irregular galaxies in the Local Group

Massive Star Formation in the Ultraviolet Observed with the Hubble Space Telescope

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