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 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 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 Theoretical investigation of the Humphreys–Davidson limit at high and low metallicity

2020 ◽  
Vol 635 ◽  
pp. A175 ◽  
Author(s):  
Erin R. Higgins ◽  
Jorick S. Vink
Keyword(s):  
Mass Loss ◽  
Massive Star ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Star Evolution ◽  
R Ratio ◽  
Red Supergiants ◽  
Low Metallicity ◽  
Massive Star Evolution

Context. Current massive star evolution grids are not able to simultaneously reproduce the empirical upper luminosity limit of red supergiants, the Humphrey–Davidson (HD) limit, nor the blue-to-red (B/R) supergiant ratio at high and low metallicity. Although previous studies have shown that the treatment of convection and semi-convection plays a role in the post-main-sequence (MS) evolution to blue or red supergiants (RSGs), a unified treatment for all metallicities has not been achieved so far. Aims. We focus on developing a better understanding of what drives massive star evolution to blue and red supergiant phases, with the ultimate aim of reproducing the HD limit at varied metallicities. We discuss the consequences of classifying B and R in the B/R ratio and clarify what is required to quantify a relatable theoretical B/R ratio for comparison with observations. Methods. For solar, Large Magellanic Cloud (50% solar), and Small Magellanic Cloud (20% solar) metallicities, we develop eight grids of MESA models for the mass range 20–60 M⊙ to probe the effect of semi-convection and overshooting on the core helium-burning phase. We compare rotating and non-rotating models with efficient (αsemi = 100) and inefficient semi-convection (αsemi = 0.1), with high and low amounts of core overshooting (αov of 0.1 or 0.5). The red and blue supergiant evolutionary phases are investigated by comparing the fraction of core He-burning lifetimes spent in each phase for a range of masses and metallicities. Results. We find that the extension of the convective core by overshooting αov = 0.5 has an effect on the post-MS evolution that can disable semi-convection, leading to more RSGs, but a lack of BSGs. We therefore implement αov = 0.1, which switches on semi-convective mixing, but for standard αsemi = 1 would result in an HD limit that is higher than observed at low Z (Large and Small Magellanic Clouds). Therefore, we need to implement very efficient semi-convection of αsemi = 100, which reproduces the HD limit at log L/L⊙ ∼ 5.5 for the Magellanic Clouds while simultaneously reproducing the Galactic HD limit of log L/L⊙ ∼ 5.8 naturally. The effect of semi-convection is not active at high metallicities because the envelope structure is depleted by strong mass loss such that semi-convective regions could not form. Conclusions. Metallicity-dependent mass loss plays an indirect, yet decisive role in setting the HD limit as a function of Z. For a combination of efficient semi-convection and low overshooting with standard Ṁ(Z), we find a natural HD limit at all metallicities.

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 Massive Star Evolution: Mass Loss and Mixing

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.

scholarly journals The Evolution of the Precursor of SN 1987 A

1988 ◽  
Vol 108 ◽  
pp. 408-409
Author(s):  
André Maeder
Keyword(s):  
Mass Loss ◽  
Massive Star ◽  
Essential Property ◽  
Solar Mass ◽  
Star Evolution ◽  
Final Mass ◽  
The Galaxy ◽  
Age Sequence ◽  
Massive Star Evolution ◽  
Hr Diagram

SummaryIdeally, the evolutionary models for the precursor of SN 1987 A should account for both the SN properties and the observational constraints for massive stars with relevant mass and composition.Mass loss is an essential property of massive star evolution. Recent parametrisations of mass loss rates for galactic stars cover the whole HR diagram. There are indications that for given L and Teff values, is lower at lower metallicity and therefore is lower in the LMC than in the Galaxy, thus we take with f < 1. Various models of an intitial 20 M⊙ star with f=0.2, 0.4, 0.6 and 1.0 are constructed (cf. Fig. 1) with a metallicity Z=0.006 and a moderate overshooting dover=0.3 Hp. From these models, we suggest an initial mass on the zero age sequence of 17 to 18 M⊙. The pre-SN location in the HR diagram very much depends on the remaining stellar mass, or more precisely on the mass of the remaining H-rich envelope. A final location at log Teff ≃ 4.2 is obtained for a final mass of about 9.0 M⊙ (cf. Fig.1). Scaled to an initial value of 17 M⊙, this corresponds to a final mass of about 8 M⊙ and a remaining H-rich envelope of a few tenths of a solar mass at most. The stellar surface exhibits CNO equilibrium values with C/N ≃ 0.01 and O/N ≃ 0.1 in mass fraction, and an hydrogen content X (surf) = 0.39. The blue progenitor is obtained for f=0.4, i.e. for -values in the LMC equal to 40% of the galactic values.

scholarly journals Luminous Blue Variables, cool hypergiants and some impostors in the H-R diagram

2003 ◽  
Vol 212 ◽  
pp. 38-46
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Surface Activity ◽  
Massive Star ◽  
Massive Stars ◽  
High Mass ◽  
Luminous Blue Variables ◽  
Star Evolution ◽  
High Mass Loss ◽  
Massive Star Evolution

Current observations of the S Dor/LBVs and candidates and the implications for their important role in massive star evolution are reviewed. Recent observations of the cool hypergiants are altering our ideas about their evolutionary state, their atmospheres and winds, and the possible mechanisms for their asymmetric high mass loss episodes which may involve surface activity and magnetic fields. Recent results for IRC+10420, ρ Cas and VY CMa are highlighted. S Dor/LBVs in eruption, and the cool hypergiants in their high mass loss phases with their optically thick winds are not what their apparent spectra and temperatures imply; they are then ‘impostors’ on the H-R diagram. The importance of the very most massive stars, like η Carinae and the ‘supernovae impostors’ are also discussed.

scholarly journals The luminosity distribution of RSGs to test their mass-loss rate

2015 ◽  
Vol 11 (A29B) ◽  
pp. 454-454 ◽  
Author(s):  
Cyril Georgy ◽  
Sylvia Ekström
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Star ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Red Supergiants ◽  
Loss Rates

AbstractThe red supergiant phase is an important phase of the evolution of massive star, as it mostly determines its final stages. One of the most important driver of the evolution during this phase is mass loss. However, the mass-loss rates prescription used for red supergiants in current stellar evolution models are still very inaccurate.Varying the mass-loss rate makes the star evolve for some time in yellow/blue regions of the HRD, modifying the number of RSGs in some luminosity ranges. Figure 1 shows how the luminosity distribution of RSGs is modified for various mass-loss prescriptions. This illustrates that it is theoretically possible to determine at least roughly what is the typical mass loss regime of RSGs in a stellar evolution perspective.

Sign in / Sign up

Export Citation Format

Share Document