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.

Formation of Ring Nebulae around Massive Stars in LMC HII Regions

1999 ◽  
Vol 190 ◽  
pp. 134-135
Author(s):  
Kerstin Weis ◽  
Wolfgang J. Duschl
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Ambient Medium ◽  
Hii Regions ◽  
Large Magellanic Cloud ◽  
High Mass ◽  
Stellar Winds ◽  
High Mass Loss ◽  
Form Ring ◽  
Ring Nebulae

Massive stars have strong stellar winds and consequently a high mass loss during their lifetimes. Therefore they can form ring nebulae by stellar winds sweeping up the ambient medium in the main sequence phase or through wind-wind interaction or eruptions in the evolved state. We present preliminary results of a search for single bubbles and ring-nebulae around massive stars in the Large Magellanic Cloud (LMC).

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 Bimodal regime in young massive clusters leading to subsequent stellar generations

2015 ◽  
Vol 12 (S316) ◽  
pp. 294-301
Author(s):  
Richard Wünsch ◽  
Jan Palouš ◽  
Guillermo Tenorio-Tagle ◽  
Casiana Muñoz-Tuñón ◽  
Soňa Ehlerová
Keyword(s):  
Stellar Evolution ◽  
Column Density ◽  
First Generation ◽  
Massive Stars ◽  
Ionising Radiation ◽  
Cluster Center ◽  
Stellar Winds ◽  
Hot Gas ◽  
Massive Clusters ◽  
By Products

AbstractMassive stars in young massive clusters insert tremendous amounts of mass and energy into their surroundings in the form of stellar winds and supernova ejecta. Mutual shock-shock collisions lead to formation of hot gas, filling the volume of the cluster. The pressure of this gas then drives a powerful cluster wind. However, it has been shown that if the cluster is massive and dense enough, it can evolve in the so–called bimodal regime, in which the hot gas inside the cluster becomes thermally unstable and forms dense clumps which are trapped inside the cluster by its gravity. We will review works on the bimodal regime and discuss the implications for the formation of subsequent stellar generations. The mass accumulates inside the cluster and as soon as a high enough column density is reached, the interior of the clumps becomes self-shielded against the ionising radiation of stars and the clumps collapse and form new stars. The second stellar generation will be enriched by products of stellar evolution from the first generation, and will be concentrated near the cluster center.

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 35. Stellar Constitution

1985 ◽  
Vol 19 (1) ◽  
pp. 479-502
Author(s):  
A. N. Cox ◽  
D. Sugimoto ◽  
P. H. Bodenheimer ◽  
C. S. Chiosi ◽  
D. J. Faulkner ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
Massive Stars ◽  
Structure Stability ◽  
Current Interest ◽  
Late Type ◽  
Dwarf Stars ◽  
Entire Field ◽  
Stellar Formation ◽  
Central Stars

This report of Commission 35, as in past reports, consists of some details of only a few selected topics. This is necessary because a survey of the entire field of stellar formation, structure, stability, evolution, pulsation, and explosions for the three year period from mid-1981 to mid-1984 would be excessively long. Our topics here, in order from the most massive stellar classes to the least are: Massive Stars (R.M. Humphreys), Rotation in Late Type Stars (W. Benz), Helioseismology (J. Christensen-Dalsgaard), Planetary Nebula Central Stars (E.M. Sion), Pulsations in Hot Degenerate Dwarf Stars (A.N. Cox and S.D. Kawaler), and White Dwarfs (V. Weidemann). There is some overlap in the reviewing of these last three reports because the topics are very closely related. Concentration in this dying stage of stellar evolution seems appropriate because of the great current interest in these matters.

scholarly journals Bubbles and Superbubbles: Observations and Theory

2007 ◽  
Vol 3 (S250) ◽  
pp. 341-354 ◽  
Author(s):  
You-Hua Chu
Keyword(s):  
Turbulent Mixing ◽  
Thermal Conduction ◽  
Massive Stars ◽  
Ambient Medium ◽  
Surrounding Medium ◽  
Shell Structures ◽  
Stellar Winds ◽  
Hot Gas ◽  
Dense Shell ◽  
Supernova Explosions

AbstractMassive stars inject energy into the surrounding medium and form shell structures. Bubbles are blown by fast stellar winds from individual massive stars, while superbubbles are blown by fast stellar winds and supernova explosions from groups of massive stars. Bubbles and superbubbles share a similar overall structure: a swept-up dense shell with an interior filled by low-density hot gas. Physical properties of a bubble/superbubble can be affected by magnetic field, thermal conduction, turbulent mixing, inhomogeneous ambient medium, etc. I will review recent progresses on observations and compare them to theoretical expectations for (1) swept-up dense shells, (2) hot interiors, and (3) interface between a dense shell and its interior hot gas.

scholarly journals How to inflate a wind-blown bubble

2021 ◽  
Vol 508 (2) ◽  
pp. 1768-1776
Author(s):  
J M Pittard ◽  
C J Wareing ◽  
M M Kupilas
Keyword(s):  
Stellar Wind ◽  
External Medium ◽  
Reference Model ◽  
Massive Stars ◽  
Ambient Medium ◽  
Stellar Winds ◽  
Relative Importance ◽  
Numerical Resolution ◽  
Maximum Value ◽  
Injection Region

ABSTRACT Stellar winds are one of several ways that massive stars can affect the star formation process on local and galactic scales. In this paper, we investigate the numerical resolution needed to inflate an energy-driven stellar wind bubble in an external medium. We find that the radius of the wind injection region, rinj, must be below a maximum value, rinj,max, in order for a bubble to be produced, but must be significantly below this value if the bubble properties are to closely agree with analytical predictions. The final bubble momentum is within 25 per cent of the value from a higher resolution reference model if χ = rinj/rinj,max = 0.1. Our work has significance for the amount of radial momentum that a wind-blown bubble can impart to the ambient medium in simulations, and thus on the relative importance of stellar wind feedback.

scholarly journals Wolf-Rayet and LBV Nebulae as the Result of Variable and Non-spherical Stellar Winds

1999 ◽  
Vol 169 ◽  
pp. 391-399 ◽  
Author(s):  
Mordecai-Mark Mac Low
Keyword(s):  
Massive Stars ◽  
Physical Basis ◽  
Stellar Winds ◽  
Central Stars

AbstractThe physical basis for interpreting observations of nebular morphology around massive stars in terms of the evolution of the central stars is reviewed, and examples are discussed, including NGC 6888, OMC-1, and η Carinae.

scholarly journals The Brightest Stars in the Magellanic Clouds and Other Late-Type Galaxies

1984 ◽  
Vol 108 ◽  
pp. 145-156
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Stellar Population ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Stellar Winds ◽  
Stellar Content ◽  
Late Type ◽  
Observational Astronomy ◽  
Distant Galaxies

The brightest stars always receive considerable attention in observational astronomy, but why are we so interested in these most luminous, and therefore most massive stars? These stars are our first probes for exploring the stellar content of distant galaxies. Admittedly, they are only the tip of the iceberg for the whole stellar population and very interesting processes are occurring among the less massive, older stars, but the most massive stars are our first indicators for studies of stellar evolution in other galaxies. They provide the first hint that stellar evolution may have been different in a particular galaxy because they evolve so quickly. The most luminous stars also highly influence their environments via their strong stellar winds and mass loss and eventually as supernovae.

scholarly journals Hollow H II Regions: From Giant to Ultracompact

1987 ◽  
Vol 115 ◽  
pp. 198-200 ◽  
Author(s):  
T. Montmerle ◽  
H. Dorland ◽  
C. Doom
Keyword(s):  
Heat Conduction ◽  
Stellar Evolution ◽  
Massive Stars ◽  
Temperature Gradients ◽  
Stellar Winds ◽  
H Ii Regions ◽  
Thick Shell ◽  
X Ray ◽  
The Standard Model ◽  
Theoretical Developments

H II regions around OB associations have a thick-shell structure (see, e.g., the Carina and Rosette nebulae), and yet the standard “Hot Interstellar Bubble” model (e.g., Weaver et al. 1977) predicts thin H II shells around a large X-ray emitting volume, when associated with stellar winds. Observations suggest that strong dissipation must occur at the edge of the wind cavity: (i) expansion velocities there are much smaller than predicted by the standard model (e.g., Chu, 1983); (ii) in bubbles around WR stars, overabundances of N, He, etc., are seen, hence the need to cool these WR-produced elements down to observable temperatures (Kwitter, 1981). Also, two theoretical developments are important: (i) new stellar evolution models for massive stars, including mass loss and overshooting in convective cores (e.g., Doom, 1985); (ii) a non-linear theory for heat conduction with steep temperature gradients (Luciani et al. 1985).

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