scholarly journals Massive star evolution in nearby galaxies

1984 ◽  
Vol 105 ◽  
pp. 279-297 ◽  
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Observational Data ◽  
Stellar Evolution ◽  
Massive Star ◽  
Stellar Content ◽  
Individual Stars ◽  
Star Evolution ◽  
Different Types ◽  
Nearby Galaxies ◽  
Massive Star Evolution

In this review I will primarily be discussing the observational data relevant to understanding the process of stellar evolution in galaxies of different types. This discussion will focus on the stellar content of the nearer galaxies; those galaxies in which the brightest individual stars are resolved and can be observed.

scholarly journals Massive Star Modeling and Nucleosynthesis

2021 ◽  
Vol 8 ◽  
Author(s):  
Sylvia Ekström
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Star ◽  
Nuclear Reactions ◽  
Massive Stars ◽  
Reaction Rates ◽  
Star Evolution ◽  
Structural Impact ◽  
Massive Star Evolution ◽  
The Impact

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.

scholarly journals Massive star evolution: feedbacks in low-Z environment

2018 ◽  
Vol 14 (S344) ◽  
pp. 153-160
Author(s):  
Sylvia Ekström ◽  
Georges Meynet ◽  
Cyril Georgy ◽  
José Groh ◽  
Arthur Choplin ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Stellar Evolution ◽  
Massive Star ◽  
Dwarf Galaxies ◽  
Massive Stars ◽  
Star Evolution ◽  
Massive Star Evolution

AbstractMassive stars are the drivers of the chemical evolution of dwarf galaxies. We review here the basics of massive star evolution and the specificities of stellar evolution in low-Z environment. We discuss nucleosynthetic aspects and what observations could constrain our view on the first generations of stars.

scholarly journals Massive star evolution revealed in the Mass-Luminosity plane

2018 ◽  
Vol 14 (S346) ◽  
pp. 480-485
Author(s):  
Erin R. Higgins ◽  
Jorick S. Vink
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Star ◽  
Main Sequence ◽  
Theoretical Models ◽  
Physical Processes ◽  
Single Star ◽  
Star Evolution ◽  
Novel Method ◽  
Massive Star Evolution

AbstractMassive star evolution is dominated by key physical processes such as mass loss, convection and rotation, yet these effects are poorly constrained, even on the main sequence. We utilise a detached, eclipsing binary HD166734 as a testbed for single star evolution to calibrate new MESA stellar evolution grids. We introduce a novel method of comparing theoretical models with observations in the ‘Mass-Luminosity Plane’, as an equivalent to the HRD (see Higgins & Vink 2018). We reproduce stellar parameters and abundances of HD166734 with enhanced overshooting (αov=0.5), mass loss and rotational mixing. When comparing the constraints of our testbed to the systematic grid of models we find that a higher value of αov=0.5 (rather than αov=0.1) results in a solution which is more likely to evolve to a neutron star than a black hole, due to a lower value of the compactness parameter.

scholarly journals Luminous Infrared Sources in the Local Group: Identifying the Missing Links in Massive Star Evolution

2014 ◽  
Vol 9 (S307) ◽  
pp. 92-93
Author(s):  
N. Britavskiy ◽  
A. Z. Bonanos ◽  
A. Mehner
Keyword(s):  
Massive Star ◽  
Local Group ◽  
Massive Stars ◽  
Star Evolution ◽  
Irregular Galaxies ◽  
Nearby Galaxies ◽  
Massive Star Evolution ◽  
Infrared Sources ◽  
Dwarf Irregular Galaxies

AbstractWe present the first systematic survey of dusty massive stars (RSGs, LBVs, sgB[e]) in nearby galaxies, with the goal of understanding their importance in massive star evolution. Using the fact that these stars are bright in mid-infrared colors due to dust, we provide a technique for selecting and identifying dusty evolved stars based on the results of Bonanos et al. (2009, 2010), Britavskiy et al. (2014), and archival Spitzer/IRAC photometry. We present the results of our spectroscopic follow-up of luminous infrared sources in the Local Group dwarf irregular galaxies: Pegasus, Phoenix, Sextans A and WLM. The survey aims to complete the census of dusty massive stars in the Local Group.

scholarly journals Massive star evolution: rotation, winds, and overshooting vectors in the mass-luminosity plane

2019 ◽  
Vol 622 ◽  
pp. A50 ◽  
Author(s):  
Erin R. Higgins ◽  
Jorick S. Vink
Keyword(s):  
Binary System ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Star ◽  
Main Sequence ◽  
Test Bed ◽  
Star Evolution ◽  
Red Supergiants ◽  
Nitrogen Abundance ◽  
Massive Star Evolution

Context. Massive star evolution is dominated by various physical effects, including mass loss, overshooting, and rotation, but the prescriptions of their effects are poorly constrained and even affect our understanding of the main sequence. Aims. We aim to constrain massive star evolution models using the unique test-bed eclipsing binary HD 166734 with new grids of MESA stellar evolution models, adopting calibrated prescriptions of overshooting, mass loss, and rotation. Methods. We introduce a novel tool, called the mass-luminosity plane or M−L plane, as an equivalent to the traditional HR diagram, utilising it to reproduce the test-bed binary HD 166734 with newly calibrated MESA stellar evolution models for single stars. Results. We can only reproduce the Galactic binary system with an enhanced amount of core overshooting (αov = 0.5), mass loss, and rotational mixing. We can utilise the gradient in the M−L plane to constrain the amount of mass loss to 0.5–1.5 times the standard prescription test-bed, and we can exclude extreme reduction or multiplication factors. The extent of the vectors in the M−L plane leads us to conclude that the amount of core overshooting is larger than is normally adopted in contemporary massive star evolution models. We furthermore conclude that rotational mixing is mandatory to obtain the correct nitrogen abundance ratios between the primary and secondary components (3:1) in our test-bed binary system. Conclusions. Our calibrated grid of models, alongside our new M−L plane approach, present the possibility of a widened main sequence due to an increased demand for core overshooting. The increased amount of core overshooting is not only needed to explain the extended main sequence, but the enhanced overshooting is also needed to explain the location of the upper-luminosity limit of the red supergiants. Finally, the increased amount of core overshooting has – via the compactness parameter – implications for supernova explodability.

scholarly journals Massive star evolution in the Small Magellanic Cloud

2003 ◽  
Vol 212 ◽  
pp. 308-315 ◽  
Author(s):  
Daniel J. Lennon
Keyword(s):  
Stellar Evolution ◽  
Massive Star ◽  
Main Sequence ◽  
Single Star ◽  
Promising Alternative ◽  
Star Models ◽  
Abundance Patterns ◽  
Star Evolution ◽  
Type Giant ◽  
Massive Star Evolution

We discuss abundances for eight early B-type giant/supergiant stars in the SMC cluster NGC 330. All are nitrogen rich with an abundance approximately 1.3 dex higher than an SMC main-sequence field. Given the number of B-type stars with low rotational projected velocities in NGC 330 (all our targets have v sin i < 50 kms–1), we suggest that it is unlikely that the stars in our sample are seen almost pole-on, but rather that they are intrinsically slow rotators. Comparing these results with the predictions of stellar evolution models including the effects of rotationally induced mixing, we conclude that while the abundance patterns may indeed be reproduced, those models with initially large rotational velocities do not reproduce the observed range of effective temperatures of our sample, nor the currently observed rotational velocities. Binary models may be able to produce stars in the observed temperature range and provide a promising alternative to single star models for explaining the observations. We also discuss the clear need for stellar evolution calculations employing the correct chemical mix of carbon, nitrogen and oxygen for the SMC.

scholarly journals The Cooler Supergiants (A to M): Crucial Signposts in the Lifecycles of Massive Stars

1986 ◽  
Vol 116 ◽  
pp. 45-59
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Stability Limit ◽  
Hydrogen Burning ◽  
Stellar Objects ◽  
Star Evolution ◽  
Different Types ◽  
The Stability ◽  
Massive Star Evolution ◽  
Hr Diagram

The intermediate and late-type supergiants are the visually brightest stars. They are among the first stellar objects observed in other galaxies and provide our first clues to the conditions of massive star evolution in galaxies of different types. They are not as massive as the hottest and most luminous stars in the upper left of the HR diagram. Nevertheless, these somewhat lower mass stars (≈20−50 M⊙) with relatively cool temperatures play a major role in our efforts to understand massive star evolution. These supergiants are usually considered to be post hydrogen burning stars, and their relative numbers in the HR diagram provide essential comparisons with models for the later stages of massive star evolution. Most importantly, the most luminous cooler supergiants define the stability limit for massive stars in the HR diagram.

What the galaxies of the Local Group tell us about massive star evolution

1999 ◽  
Vol 193 ◽  
pp. 429-440
Author(s):  
Philip Massey
Keyword(s):  
Massive Star ◽  
Local Group ◽  
Relative Number ◽  
Mass Range ◽  
Large Mass ◽  
High Mass ◽  
Starburst Galaxy ◽  
Stellar Content ◽  
Star Evolution ◽  
Massive Star Evolution

We consider what we've learned about massive star evolution from observations of the resolved stellar content of Local Group galaxies. Studies of mixed-age (galaxy-wide) and coeval (single associations) populations reveal much about massive star evolution, and how it is controlled by metallicity, demonstrating the ‘Conti scenario’ in action! The number of WC stars to WN stars increases with increasing metallicity, as expected: in regions of higher metallicity stars of somewhat lower luminosity can evolve all the way to the WC stage. The exception is the starburst galaxy IC 10, for which I speculate that the IMF may be weighted towards high mass stars. The highest luminosity red supergiants are lacking in galaxies of higher metallicity, suggesting that the stars that would have become these RSGs are spending more of their time as WRs. The presence of luminous RSGs is highly correlated with the presence of WC and WN stars in OB associations, suggesting that many massive stars evolve through both a RSG and WR stage. The relative number of RSGs and WRs does decrease strongly with increasing metallicity, again consistent with higher metallicity systems leading to increased time in the WR phase. The various WC subclasses appear to be the result of the influence of metallicity on stellar wind structure in these stars, and are not due to to differences in mass or luminosity. Data on the field population in the Magellanic Clouds suggest that stars more massive than 30 become WRs in the LMC, while the limit may be more like 50 in the SMC, again as expected. Studies of the turn-off masses in clusters and associations in the MCs and Milky Way are nearing completion, while investigations in the more distant galaxies of the Local Group are just getting underway. For the LMC we find the following: WNE stars come from a large mass range of progenitor (30–100 ), and have very large (negative) bolometric corrections (−6 to −8 mag). The Ofpe/WN9 stars seem to come from lower mass progenitor (20–30 ), and have more modest BCs (−1 to −3 mag). WC stars come from stars with masses > 60–70 , and have BCs of −3 to −4 mag. Both ‘B2I+WN3’ systems and LBV stars like S Doradus are found only in clusters containing very high turn off masses (>70–90 ).

scholarly journals Bridging the gap: from massive stars to supernovae

2017 ◽  
Vol 375 (2105) ◽  
pp. 20170025 ◽  
Author(s):  
Justyn R. Maund ◽  
Paul A. Crowther ◽  
Hans-Thomas Janka ◽  
Norbert Langer
Keyword(s):  
Stellar Evolution ◽  
Observational Studies ◽  
Massive Star ◽  
Massive Stars ◽  
Scientific Meeting ◽  
The Other ◽  
Star Evolution ◽  
Massive Star Evolution ◽  
The Universe ◽  
Key Questions

Almost since the beginning, massive stars and their resultant supernovae have played a crucial role in the Universe. These objects produce tremendous amounts of energy and new, heavy elements that enrich galaxies, encourage new stars to form and sculpt the shapes of galaxies that we see today. The end of millions of years of massive star evolution and the beginning of hundreds or thousands of years of supernova evolution are separated by a matter of a few seconds, in which some of the most extreme physics found in the Universe causes the explosive and terminal disruption of the star. Key questions remain unanswered in both the studies of how massive stars evolve and the behaviour of supernovae, and it appears the solutions may not lie on just one side of the explosion or the other or in just the domain of the stellar evolution or the supernova astrophysics communities. The need to view massive star evolution and supernovae as continuous phases in a single narrative motivated the Theo Murphy international scientific meeting ‘Bridging the gap: from massive stars to supernovae’ at Chicheley Hall, UK, in June 2016, with the specific purpose of simultaneously addressing the scientific connections between theoretical and observational studies of massive stars and their supernovae, through engaging astronomers from both communities. This article is part of the themed issue ‘Bridging the gap: from massive stars to supernovae’.

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