The Point on the Theoretical Changes of Surface Chemistry During Massive Star Evolution

For main sequence stars, the central nuclear processing generally has no effect on surface abundances. Later in the evolution, the newly synthetized elements may be revealed at the stellar surface by processes such as mass loss, convective dredge-up, overshooting, diffusion, rotational and tidal mixing, etc. The changes of CNO abundances are the most conspicuous and the easiest to observe spectroscopically; some abundance ratios like C/N, O/N may undergo changes by more than 102. On the whole, surface chemistry is a most powerful diagnostics of stellar evolution, model assumptions and nuclear cross sections.

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The point on the theoretical changes of surface chemistry during massive star evolution

Atmospheric Diagnostics of Stellar Evolution: Chemical Peculiarity, Mass Loss, and Explosion - Lecture Notes in Physics ◽

10.1007/bfb0034559 ◽

2006 ◽

pp. 79-85

Author(s):

André Maeder

Keyword(s):

Surface Chemistry ◽

Massive Star ◽

Star Evolution ◽

Massive Star Evolution

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Massive star evolution revealed in the Mass-Luminosity plane

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319001170 ◽

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.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834123 ◽

2019 ◽

Vol 622 ◽

pp. A50 ◽

Cited By ~ 10

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.

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Wolf Rayet stars in galaxies and the role of binaries and hydrodynamics

Symposium - International Astronomical Union ◽

10.1017/s0074180900202143 ◽

1995 ◽

Vol 163 ◽

pp. 280-290

Author(s):

André Maeder

Keyword(s):

Mass Transfer ◽

Massive Star ◽

Main Sequence ◽

Stellar Winds ◽

Star Evolution ◽

Model Independent ◽

Domain Of Parameters ◽

Massive Star Evolution ◽

Good Agreement

WR stars obey M-L-·-Teff-R-chemistry relations, which are in general model independent (with the exception of chemistry). The processes of WR formation (stellar winds, hydrodynamical mixing, binary mass transfer etc.) influence, however, the domain of parameters occupied by WR stars. We specifically examine the distribution of luminosities and H-contents of WN stars, which both support heavy mass loss rates, or possibly mixing, in the main sequence and WNL phases. Detailed studies of the number ratios WR/O, WC/WN, WC/WR, etc. are made for galaxies at various metallicities Z which exhibit extremely different WR populations. Good agreement of models and observations is found. It is also shown that the data are better explained if a certain fraction Φ (less than 10%) of the O-stars become WR stars, preferentially of type WNE as a result of Roche lobe overflow (RLOF) in binaries. This result necessarily implies that the fraction of WR stars, owing their existence to RLOF, is variable with Z, being nearly 100% at low Z and much smaller at high Z. We also identify several hydrodynamical developments physically required in stellar models. Among them, we collect the available observational and theoretical arguments supporting an important role of mixing in massive star evolution.

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Massive star evolution in the Small Magellanic Cloud

Symposium - International Astronomical Union ◽

10.1017/s0074180900212370 ◽

2003 ◽

Vol 212 ◽

pp. 308-315 ◽

Cited By ~ 2

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.

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Properties of OB star−black hole systems derived from detailed binary evolution models

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937375 ◽

2020 ◽

Vol 638 ◽

pp. A39 ◽

Cited By ~ 12

Author(s):

N. Langer ◽

C. Schürmann ◽

K. Stoll ◽

P. Marchant ◽

D. J. Lennon ◽

...

Keyword(s):

Black Holes ◽

Black Hole ◽

Radial Velocity ◽

Massive Star ◽

Main Sequence ◽

X Ray ◽

Black Hole Binaries ◽

Star Evolution ◽

Binary Evolution ◽

Massive Star Evolution

Context. The recent gravitational wave measurements have demonstrated the existence of stellar mass black hole binaries. It is essential for our understanding of massive star evolution to identify the contribution of binary evolution to the formation of double black holes. Aims. A promising way to progress is investigating the progenitors of double black hole systems and comparing predictions with local massive star samples, such as the population in 30 Doradus in the Large Magellanic Cloud (LMC). Methods. With this purpose in mind, we analysed a large grid of detailed binary evolution models at LMC metallicity with initial primary masses between 10 and 40 M⊙, and identified the model systems that potentially evolve into a binary consisting of a black hole and a massive main-sequence star. We then derived the observable properties of such systems, as well as peculiarities of the OB star component. Results. We find that ∼3% of the LMC late-O and early-B stars in binaries are expected to possess a black hole companion when stars with a final helium core mass above 6.6 M⊙ are assumed to form black holes. While the vast majority of them may be X-ray quiet, our models suggest that these black holes may be identified in spectroscopic binaries, either by large amplitude radial velocity variations (≳50 km s−1) and simultaneous nitrogen surface enrichment, or through a moderate radial velocity (≳10 km s−1) and simultaneous rapid rotation of the OB star. The predicted mass ratios are such that main-sequence companions can be excluded in most cases. A comparison to the observed OB+WR binaries in the LMC, Be and X-ray binaries, and known massive black hole binaries supports our conclusion. Conclusions. We expect spectroscopic observations to be able to test key assumptions in our models, with important implications for massive star evolution in general and for the formation of double black hole mergers in particular.

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Massive Star Evolution: Mass Loss and Mixing

Symposium - International Astronomical Union ◽

10.1017/s0074180900149137 ◽

1986 ◽

Vol 116 ◽

pp. 287-300

Author(s):

André Maeder

Keyword(s):

Mass Loss ◽

Massive Star ◽

Main Sequence ◽

Relative Mass ◽

Physical Processes ◽

Mixing Processes ◽

Physical Reason ◽

Star Evolution ◽

Massive Star Evolution ◽

Evolutionary Consequences

At first it may be surprising that mass loss, overshooting and mixing, which are indeed very different physical processes, have similar consequences on stellar evolution. These various processes may increase the Main-Sequence (MS) lifetime, extend the width of the MS, bring CNO-processed materials to stellar surfaces and, in extreme cases, lead to quasi-homogeneous evolution. The physical reason of this similarity is that these processes increase the relative mass fraction of the stellar cores. Thus we understand that, on the basis of their evolutionary consequences, it may not be easy to disentangle the contributions of mass loss, overshooting and mixing processes. The present status of our knowledge on these effects, which appear to have major consequences on the evolution of massive stars, is now examined in detail.

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Outflowing Envelopes From Stars at Arbitrary Optical Depths a New Approach to the Problem

Highlights of Astronomy ◽

10.1017/s1539299600021316 ◽

1998 ◽

Vol 11 (1) ◽

pp. 381-381

Author(s):

A.V. Dorodnitsyn

Keyword(s):

Differential Equations ◽

Massive Star ◽

System Of Differential Equations ◽

Continuous Transition ◽

Satisfactory Description ◽

Sonic Point ◽

New Approach ◽

Star Evolution ◽

Matter Flux ◽

Massive Star Evolution

We have considered a stationary outflowing envelope accelerated by the radiative force in arbitrary optical depth case. Introduced approximations provide satisfactory description of the behavior of the matter flux with partially separated radiation at arbitrary optical depths. The obtained systemof differential equations provides a continuous transition of the solution between optically thin and optically thick regions. We analytically derivedapproximate representation of the solution at the vicinity of the sonic point. Using this representation we numerically integrate the system of equations from the critical point to the infinity. Matching the boundary conditions we obtain solutions describing the problem system of differential equations. The theoretical approach advanced in this work could be useful for self-consistent simulations of massive star evolution with mass loss.

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