scholarly journals Massive stars in their death throes

2008 ◽  
Vol 366 (1884) ◽  
pp. 4441-4452 ◽  
Author(s):  
John J Eldridge
Keyword(s):  
Stellar Evolution ◽  
Massive Stars ◽  
Evolution Theory ◽  
Luminous Blue Variables ◽  
Show Evidence ◽  
Red Supergiants ◽  
Working Backwards

The study of the stars that explode as supernovae used to be a forensic study, working backwards from the remnants of the star. This changed in 1987 when the first progenitor star was identified in pre-explosion images. Currently, there are eight detected progenitors with another 21 non-detections, for which only a limit on the pre-explosion luminosity can be placed. This new avenue of supernova research has led to many interesting conclusions, most importantly that the progenitors of the most common supernovae, type IIP, are red supergiants, as theory has long predicted. However, no progenitors have been detected thus far for the hydrogen-free type Ib/c supernovae, which, given the expected progenitors, is an unlikely result. Also, observations have begun to show evidence that luminous blue variables, which are among the most massive stars, may directly explode as supernovae. These results contradict the current stellar evolution theory. This suggests that we may need to update our understanding.

scholarly journals Predicting the nature of supernova progenitors

2017 ◽  
Vol 375 (2105) ◽  
pp. 20170219 ◽  
Author(s):  
Jose H. Groh
Keyword(s):  
High Resolution ◽  
Physical Properties ◽  
Stellar Evolution ◽  
Massive Stars ◽  
High Resolution Spectrum ◽  
Core Collapse ◽  
Single Star ◽  
Luminous Blue Variables ◽  
Star Models ◽  
Red Supergiants

Stars more massive than about 8 solar masses end their lives as a supernova (SN), an event of fundamental importance Universe-wide. The physical properties of massive stars before the SN event are very uncertain, both from theoretical and observational perspectives. In this article, I briefly review recent efforts to predict the nature of stars before death, in particular, by performing coupled stellar evolution and atmosphere modelling of single stars in the pre-SN stage. These models are able to predict the high-resolution spectrum and broadband photometry, which can then be directly compared with the observations of core-collapse SN progenitors. The predictions for the spectral types of massive stars before death can be surprising. Depending on the initial mass and rotation, single star models indicate that massive stars die as red supergiants, yellow hypergiants, luminous blue variables and Wolf–Rayet stars of the WN and WO subtypes. I finish by assessing the detectability of SN Ibc progenitors. This article is part of the themed issue ‘Bridging the gap: from massive stars to supernovae’.

scholarly journals Ring Nebulae Around Massive Stars

1991 ◽  
Vol 143 ◽  
pp. 349-364
Author(s):  
You-Hua Chu
Keyword(s):  
Stellar Evolution ◽  
Spectral Properties ◽  
Massive Stars ◽  
Ambient Medium ◽  
Stellar Winds ◽  
Luminous Blue Variables ◽  
Stellar Properties ◽  
Ring Nebulae ◽  
Central Stars ◽  
Temperature Correlations

Ring nebulae have been found around WR stars, OB and Of stars, and luminous blue variables. Ring nebulae are formed by the interaction between the central stars and their ambient medium via different combinations of stellar winds, ejecta, and radiation. The spectral properties of the nebulae can be used to diagnose the stellar properties, such as luminosity and effective temperature. Correlations between ring nebulae and their central stars may be used to check scenarios of stellar evolution.

scholarly journals Dusty LBV Nebulae: Tracing the Mass Loss History of the Most Massive Stars

1999 ◽  
Vol 169 ◽  
pp. 381-390
Author(s):  
Laurens B.F.M. Waters ◽  
Robert H.M. Voors ◽  
Patrick W. Morris ◽  
Norman R. Trams ◽  
Alex de Koter ◽  
...  
Keyword(s):  
Massive Stars ◽  
High Ratio ◽  
Agb Stars ◽  
Space Observatory ◽  
Dust Shells ◽  
Luminous Blue Variables ◽  
Dust Composition ◽  
Red Supergiants ◽  
History Of ◽  
Similar Processing

AbstractWe present spectra obtained with the Infared Space Observatory (ISO) of the dust shells surrounding several Luminous Blue Variables (LBVs), both in our galaxy and in the LMC. The 20-45 μm spectra of R71, AG Car and Wra 751 show prominent emission features from crystalline silicates. The composition of the crystalline silicates in LBV dust shells is compared to that found in other types of objects, such as (post)-AGB stars and red supergiants (RSG). Both Wra 751 and AG Car have a high ratio of pyroxenes to olivines. This suggests that the grains in both stars experienced very similar processing, but that this processing has lead to a higher abundance of pyroxenes compared to RSG. The dust composition of the three LBVs discussed here suggests dust formation in a cool outflow not unlike those of RSG.

scholarly journals About the Luminous Blue Variable He3-519

2010 ◽  
Vol 6 (S272) ◽  
pp. 87-88
Author(s):  
Anthony Hervé ◽  
Jean-Claude Bouret
Keyword(s):  
Stellar Evolution ◽  
Time Scale ◽  
Massive Stars ◽  
Model Atmosphere ◽  
Transition Phase ◽  
Evolutionary Status ◽  
Stellar Winds ◽  
Luminous Blue Variables ◽  
Luminous Blue Variable

AbstractLuminous Blue Variables (LBVs) are massive stars, in a transition phase, from being O-type stars and rapidly becoming Wolf-Rayet objects. LBVs possess powerful stellar winds, high luminosities and show photometric and spectroscopic variability. We present the stellar and wind parameters of He3-519 obtained by the modeling of UVES observations with the model atmosphere code CMFGEN. We compare our results to previous studies in order to find mid-time scale variability of the stellar parameters and finally, we use stellar evolution models to determine the evolutionary status of this star.

scholarly journals New prescriptions of turbulent transport from local numerical simulations

2014 ◽  
Vol 9 (S307) ◽  
pp. 70-75
Author(s):  
V. Prat ◽  
F. Lignières ◽  
G. Lesur
Keyword(s):  
Numerical Simulations ◽  
Stellar Evolution ◽  
Turbulent Mixing ◽  
Massive Stars ◽  
Turbulent Transport ◽  
Strong Impact ◽  
Evolution Theory ◽  
Transport Models ◽  
Chemical Stratification ◽  
The Impact

AbstractMassive stars often experience fast rotation, which is known to induce turbulent mixing with a strong impact on the evolution of these stars. Local direct numerical simulations of turbulent transport in stellar radiative zones are a promising way to constrain phenomenological transport models currently used in many stellar evolution codes. We present here the results of such simulations of stably-stratified sheared turbulence taking notably into account the effects of thermal diffusion and chemical stratification. We also discuss the impact of theses results on stellar evolution theory.

scholarly journals Pulsation and mass loss across the H-R diagram: From OB stars to Cepheids to red supergiants

2013 ◽  
Vol 9 (S301) ◽  
pp. 205-212
Author(s):  
Hilding R. Neilson
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Massive Stars ◽  
Main Sequence Stars ◽  
Ob Stars ◽  
Classical Cepheids ◽  
Growing Body ◽  
Red Supergiants ◽  
Enhance Mass

AbstractBoth pulsation and mass loss are commonly observed in stars and are important ingredients for understanding stellar evolution and structure, especially for massive stars. There is a growing body of evidence that pulsation can also drive and enhance mass loss in massive stars and that pulsation-driven mass loss is important for stellar evolution. In this review, I will discuss recent advances in understanding pulsation-driven mass loss in massive main-sequence stars, classical Cepheids and red supergiants and present some challenges remaining.

scholarly journals The effect of rotation on RGB surface abundances

1997 ◽  
Vol 189 ◽  
pp. 349-354
Author(s):  
C. Charbonnel
Keyword(s):  
Stellar Evolution ◽  
Globular Cluster ◽  
Massive Stars ◽  
Observational Evidence ◽  
Evolution Theory ◽  
Mixing Processes ◽  
Giant Stars ◽  
The Subject ◽  
Abundance Anomalies ◽  
Chemical Anomalies

Pop II field and globular cluster giant stars (and, to a less extent, Pop I giants) exhibit chemical anomalies which are not predicted by standard stellar evolution theory. Two hypotheses have been proposed to explain these abundance variations, namely the primordial and the evolutionary explanations. A primordial origin for intracluster abundance anomalies (see e.g. Cottrel & Da Costa 1981) would be related to inhomogeneities in the cluster material due to pollution by a prior generation of massive stars. In the evolutionary hypothesis, abundance variations would be due to nuclear and mixing processes internal to the giant stars themselves. Many good reviews exist on the subject (see e.g. Briley et al. 1994a, Kraft 1994), in which observational evidence supporting both hypotheses are presented. In this conference, Da Costa recalls the most recent observational data, and some excellent poster contributions bring essential clues to the subject.

scholarly journals Grids of stellar models with rotation

2019 ◽  
Vol 627 ◽  
pp. A24 ◽  
Author(s):  
J. H. Groh ◽  
S. Ekström ◽  
C. Georgy ◽  
G. Meynet ◽  
A. Choplin ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Massive Stars ◽  
Stellar Winds ◽  
Pulsation Period ◽  
Instability Strip ◽  
Helium Burning ◽  
Red Supergiants ◽  
Low Metallicity ◽  
Effects Of Rotation ◽  
The Impact

The effects of rotation on stellar evolution are particularly important at low metallicity, when mass loss by stellar winds diminishes and the surface enrichment due to rotational mixing becomes relatively more pronounced than at high metallicities. Here we investigate the impact of rotation and metallicity on stellar evolution. Using similar physics as in our previous large grids of models at Z = 0.002 and Z = 0.014, we compute stellar evolution models with the Geneva code for rotating and nonrotating stars with initial masses (Mini) between 1.7 and 120 M⊙ and Z = 0.0004 (1/35 solar). This is comparable to the metallicities of the most metal poor galaxies observed so far, such as I Zw 18. Concerning massive stars, both rotating and nonrotating models spend most of their core-helium burning phase with an effective temperature higher than 8000 K. Stars become red supergiants only at the end of their lifetimes, and few red supergiants are expected. Our models predict very few to no classical Wolf–Rayet stars as a results of weak stellar winds at low metallicity. The most massive stars end their lifetimes as luminous blue supergiants or luminous blue variables, a feature that is not predicted by models with higher initial metallicities. Interestingly, due to the behavior of the intermediate convective zone, the mass domain of stars producing pair-instability supernovae is smaller at Z = 0.0004 than at Z = 0.002. We find that during the main sequence (MS) phase, the ratio between nitrogen and carbon abundances (N/C) remains unchanged for nonrotating models. However, N/C increases by factors of 10–20 in rotating models at the end of the MS. Cepheids coming from stars with Mini >  4 − 6 M⊙ are beyond the core helium burning phase and spend little time in the instability strip. Since they would evolve towards cooler effective temperatures, these Cepheids should show an increase of the pulsation period as a function of age.

scholarly journals Common envelope evolution of massive stars

2018 ◽  
Vol 14 (S346) ◽  
pp. 449-454 ◽  
Author(s):  
Paul M. Ricker ◽  
Frank X. Timmes ◽  
Ronald E. Taam ◽  
Ronald F. Webbink
Keyword(s):  
Black Hole ◽  
Stellar Evolution ◽  
Massive Stars ◽  
Evolution Theory ◽  
Helium Burning ◽  
Massive Black Hole ◽  
Common Envelope ◽  
Binary Black Hole ◽  
Low Metallicity ◽  
The Common

AbstractThe discovery via gravitational waves of binary black hole systems with total masses greater than 60Mʘ has raised interesting questions for stellar evolution theory. Among the most promising formation channels for these systems is one involving a common envelope binary containing a low metallicity, core helium burning star with mass ⁓30 – 40Mʘ and a black hole with mass ⁓30 – 40Mʘ. For this channel to be viable, the common envelope binary must eject more than half the giant star’s mass and reduce its orbital separation by as much as a factor of 80. We discuss issues faced in numerically simulating the common envelope evolution of such systems and present a 3D AMR simulation of the dynamical inspiral of a low-metallicity red supergiant with a massive black hole companion.

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