scholarly journals The Complex Upper HR Diagram

Galaxies ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 75
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Historical Overview ◽  
Ob Stars ◽  
Luminous Blue Variables ◽  
Evolved Stars ◽  
Nearby Galaxies ◽  
Introductory Review ◽  
Hr Diagram

Several decades of observations of the most massive and most luminous stars have revealed a complex upper HR Diagram, shaped by mass loss, and inhabited by a variety of evolved stars exhibiting the consequences of their mass loss histories. This introductory review presents a brief historical overview of the HR Diagram for massive stars, highlighting some of the primary discoveries and results from their observation in nearby galaxies. The sections in this volume include reviews of our current understanding of different groups of evolved massive stars, all losing mass and in different stages of their evolution: the Luminous Blue Variables (LBVs), B[e] supergiants, the warm hypergiants, Wolf–Rayet stars, and the population of OB stars and supergiants in the Magellanic Clouds.

scholarly journals Red Supergiants, Yellow Hypergiants, and Post-RSG Evolution

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 92 ◽  
Author(s):  
Michael S. Gordon ◽  
Roberta M. Humphreys
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Terminal State ◽  
High Mass ◽  
Luminous Blue Variables ◽  
High Mass Loss ◽  
Red Supergiants ◽  
Wind Activity ◽  
Open Question ◽  
Hr Diagram

How massive stars end their lives remains an open question in the field of star evolution. While the majority of stars above ≳9 M ⊙ will become red supergiants (RSGs), the terminal state of these massive stars can be heavily influenced by their mass-loss histories. Periods of enhanced circumstellar wind activity can drive stars off the RSG branch of the HR Diagram. This phase, known as post-RSG evolution, may well be tied to high mass-loss events or eruptions as seen in the Luminous Blue Variables (LBVs) and other massive stars. This article highlights some of the recent observational and modeling studies that seek to characterize this unique class of stars, the post-RSGs and link them to other massive objects on the HR Diagram such as LBVs, Yellow Hypergiants and dusty RSGs.

scholarly journals The properties of early-type stars in the Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 325-336
Author(s):  
Christopher J. Evans
Keyword(s):  
Physical Properties ◽  
Mass Loss ◽  
Temperature Scale ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Early Type ◽  
The Past ◽  
The Galaxy ◽  
Stellar Temperature ◽  
Early Type Stars

AbstractThe past decade has witnessed impressive progress in our understanding of the physical properties of massive stars in the Magellanic Clouds, and how they compare to their cousins in the Galaxy. I summarise new results in this field, including evidence for reduced mass-loss rates and faster stellar rotational velocities in the Clouds, and their present-day compositions. I also discuss the stellar temperature scale, emphasizing its dependence on metallicity across the entire upper-part of the Hertzsprung-Russell diagram.

scholarly journals Spectroscopic studies of OB stars in the Magellanic Clouds with VLT-UVES

2003 ◽  
Vol 212 ◽  
pp. 176-177
Author(s):  
Christopher J. Evans ◽  
Paul A. Crowther ◽  
Alexander W. Fullerton ◽  
D. John Hillier
Keyword(s):  
Mass Loss ◽  
Model Atmosphere ◽  
Spectroscopic Studies ◽  
Magellanic Clouds ◽  
Ob Stars ◽  
Plane Parallel ◽  
Parallel Models ◽  
Cno Abundances ◽  
Loss Rates

We present results from optical and ultraviolet analysis of nine LMC/SMC supergiants. Temperatures, mass-loss rates and CNO abundances are obtained using the non-LTE, line-blanketed model atmosphere code of Hillier & Miller (1998). In general, the derived temperatures are significantly lower than those determined from unblanketed, plane-parallel models.

scholarly journals Mass loss and evolution of massive stars in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 480-482 ◽  
Author(s):  
Claus Leitherer ◽  
Norbert Langer
Keyword(s):  
Mass Loss ◽  
Iterative Procedure ◽  
Metal Content ◽  
Loss Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
Magellanic Clouds ◽  
Evolutionary Models ◽  
Low Metallicity ◽  
Self Consistency

The structure and evolution of massive stars is significantly influenced by effects of chemical composition in a low-metallicity environment (as compared to the solar neighbourhood, SN), such as the Magellanic Clouds. A fundamental ingredient in evolutionary models is the stellar mass-loss rate M. Lower metal content decreases the mass-loss rates derived theoretically, which in turn affects the stellar evolution models. On the other hand, different evolutionary models predict different stellar parameters (especially L), which again influence M so that an iterative procedure is required to achieve self-consistency.

29. Stellar Spectra (Spectres Stellaires)

1991 ◽  
Vol 21 (1) ◽  
pp. 309-326
Keyword(s):  
Milky Way ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Dynamical Interaction ◽  
Stellar Spectra ◽  
Luminous Blue Variables ◽  
Classical Novae ◽  
Giant Stars ◽  
Red Giant ◽  
Sydney Australia

In the triennium under review, from the late second half of 1987 to the early second half of 1990, Commission 29 has sponsored or cosponsored the following IAU Conferences: Coll. No. 106, “Evolution of Peculiar Red Giant Stars,” Bloomington, Indiana, July 1988; CoU. No. 114, “White Dwarfs,” Hanover, New Hamsphire, August 1988; Coll. No. 113, “Physics of Luminous Blue Variables,” Val Morin, Quebec, August 1988; Coll. No. 122, “Physics of Classical Novae,” Madrid, Spain, June 1989; Symp. No. 143, “Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies,” Denpasar, Indonesia, June 1990; Symp. No 148, “The Magellanic Clouds and their Dynamical Interaction with the Milky Way,” Sydney, Australia, July 1990; Symp. No. 145, “Evolution of Stars: the Photospheric Abundance Connection,” Druzba, Bulgaria. August 1990.

scholarly journals Mass loss from early-type stars

1970 ◽  
Vol 36 ◽  
pp. 209-212
Author(s):  
J. B. Hutchings
Keyword(s):  
Mass Loss ◽  
Spectral Type ◽  
Stellar Evolution ◽  
Early Type ◽  
High Luminosity ◽  
Spectroscopic Evidence ◽  
Ob Stars ◽  
Early Type Stars ◽  
Very High ◽  
Hr Diagram

Following the detailed study of four very high luminosity OB stars, a survey has been made for spectroscopic evidence of mass loss in a number of early-type supergiants. A list of spectroscopic criteria is given and the mass loss estimates for 24 stars plotted on the HR diagram. The dependence of the phenomenon on spectral type and luminosity is discussed as well as its significance in terms of stellar evolution.

scholarly journals Working Group on Hot Massive Stars (Groupe De Travail Sur Les Etoiles Massives Chaudes)

2000 ◽  
Vol 24 (1) ◽  
pp. 176-185
Author(s):  
Philippe Eenens ◽  
Joseph Cassinelli ◽  
Peter Conti ◽  
Catharine Garmany ◽  
Karel van der Hucht ◽  
...  
Keyword(s):  
Executive Committee ◽  
Working Group ◽  
Collaborative Research ◽  
Massive Stars ◽  
Starburst Galaxies ◽  
General Assembly ◽  
Hot Stars ◽  
Ob Stars ◽  
Luminous Blue Variables

The Working Group on Hot Massive Stars has been officially recognized by the IAU Executive Committee during the XXIII General Assembly in August 1997. Its origins are the Hot Star Newsletter, launched in 1994, and a long tradition of interaction and collaborative research strengthened by a series of meetings on hot beaches. It gathers over 500 researchers working on OB stars, Luminous Blue Variables, Wolf-Rayet stars, and in general all topics related to the evolution of massive stars and to the physics and consequences of winds from hot stars. The very successful recent symposium on “Wolf-Rayet phenomena in massive stars and starburst galaxies” is an indicator of the increasing interest of the extragalactic community in the study of these extraordinary stars.

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.

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