scholarly journals Luminous Blue Variables

Galaxies ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 20 ◽  
Author(s):  
Kerstin Weis ◽  
Dominik J. Bomans
Keyword(s):  
Massive Stars ◽  
Current Knowledge ◽  
Variable Mass ◽  
Time Variable ◽  
Host Galaxies ◽  
Identification Scheme ◽  
Luminous Blue Variables ◽  
Evolved Stars ◽  
Η Car

Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or η Car analogs and the S Dor cycle LBVs.

scholarly journals A Census of B[e] Supergiants

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 83 ◽  
Author(s):  
Michaela Kraus
Keyword(s):  
Main Sequence ◽  
Massive Stars ◽  
Unknown Origin ◽  
Large Mass ◽  
Physical Parameters ◽  
Main Sequence Stars ◽  
Luminous Blue Variables ◽  
Spectroscopic Characteristics ◽  
Dusty Disks

Stellar evolution theory is most uncertain for massive stars. For reliable predictions of the evolution of massive stars and their final fate, solid constraints on the physical parameters, and their changes along the evolution and in different environments, are required. Massive stars evolve through a variety of short transition phases, in which they can experience large mass-loss either in the form of dense winds or via sudden eruptions. The B[e] supergiants comprise one such group of massive transition objects. They are characterized by dense, dusty disks of yet unknown origin. In the Milky Way, identification and classification of B[e] supergiants is usually hampered by their uncertain distances, hence luminosities, and by the confusion of low-luminosity candidates with massive pre-main sequence objects. The extragalactic objects are often mistaken as quiescent or candidate luminous blue variables, with whom B[e] supergiants share a number of spectroscopic characteristics. In this review, proper criteria are provided, based on which B[e] supergiants can be unambiguously classified and separated from other high luminosity post-main sequence stars and pre-main sequence stars. Using these criteria, the B[e] supergiant samples in diverse galaxies are critically inspected, to achieve a reliable census of the current population.

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 Massive stars in extremely metal-poor galaxies: a window into the past

2021 ◽  
Author(s):  
Miriam Garcia ◽  
Christopher J. Evans ◽  
Joachim M. Bestenlehner ◽  
Jean Claude Bouret ◽  
Norberto Castro ◽  
...  
Keyword(s):  
Metal Content ◽  
Hubble Space Telescope ◽  
Massive Stars ◽  
Current Knowledge ◽  
Single Point ◽  
White Paper ◽  
Host Galaxies ◽  
New Paradigm ◽  
Space Telescope ◽  
The Universe

AbstractCosmic history has witnessed the lives and deaths of multiple generations of massive stars, all of them invigorating their host galaxies with ionizing photons, kinetic energy, fresh material, and stellar-mass black holes. Ubiquitous engines as they are, astrophysics needs a good understanding of their formation, evolution, properties and yields throughout the history of the Universe, and with decreasing metal content mimicking the environment at the earliest epochs. Ultimately, a physical model that could be extrapolated to zero metallicity would enable tackling long-standing questions such as “What did the first, very massive stars of the Universe look like?” or “What was their role in the re-ionization of the Universe?” Yet, most of our knowledge of metal-poor massive stars is drawn from one single point in metallicity. Massive stars in the Small Magellanic Cloud (SMC, $\sim $ ∼ 1/5Z⊙ ) currently serve as templates for low-metallicity objects in the early Universe, even though significant differences with respect to massive stars with poorer metal content have been reported. This White Paper summarizes the current knowledge on extremely (sub-SMC) metal poor massive stars, highlighting the most outstanding open questions and the need to supersede the SMC as standard. A new paradigm can be built from nearby extremely metal-poor galaxies that make a new metallicity ladder, but massive stars in these galaxies are out of reach to current observational facilities. Such a task would require an L-size mission, consisting of a 10m-class space telescope operating in the optical and the ultraviolet ranges. Alternatively, we propose that ESA unites efforts with NASA to make the LUVOIR mission concept a reality, thus continuing the successful partnership that made the Hubble Space Telescope one of the greatest observatories of all time.

scholarly journals Not so lonely: The LBV binary HR Car

2016 ◽  
Vol 12 (S329) ◽  
pp. 440-440
Author(s):  
T. Rivinius ◽  
H. M. J. Boffin ◽  
A. Mérand ◽  
A. Mehner ◽  
J.-B. LeBouquin ◽  
...  
Keyword(s):  
Massive Stars ◽  
Luminous Blue Variables ◽  
Η Car

AbstractLuminous Blue Variables (LBVs) are a brief phase in the evolution of massive stars, but a very important one. The giant eruptions remain enigmatic, but the discovery of the flagship LBV η Car to be a five-year highly eccentric binary put focus on possible binarity induced mechanism for these outbursts, and prompted binarity searches among LBVs. While several wide LBV binaries were identified, HR Car is the first system found to be similar to η Car, i.e., relatively close & eccentric.

Analysis of Aluminium Beam-to-Column Joints by the Component Method: Existing Studies and Research Needs

2016 ◽  
Vol 710 ◽  
pp. 409-414 ◽  
Author(s):  
Gianfranco De Matteis ◽  
Giuseppe Brando
Keyword(s):  
Current Knowledge ◽  
Component Method ◽  
The Past ◽  
Research Fields ◽  
Numerical Studies ◽  
Current State ◽  
Moment Resisting ◽  
New Research ◽  
Steel Joints

This paper aims at providing an overview on the current state of the art and on possible future developments concerning the component method implementation for the classification of beam-to-column joints belonging to aluminum moment resisting frames.After a brief discussion on the component method theoretical bases, developed in the past to give a feasible calculation procedure for steel joints, recent experimental and numerical studies, carried out for investigating some aluminum components, are presented and discussed. In particular strengths and weaknesses of the current knowledge are put into evidence, also in light of the peculiarities that make aluminum alloys different from steel. The launch of new research fields, aimed at pursuing an update of the current codes dealing with aluminum structures, is therefore proposed.

Advances in the Biology and Genetics of the Podocytopathies: Implications for Diagnosis and Therapy

2009 ◽  
Vol 133 (2) ◽  
pp. 201-216 ◽  
Author(s):  
Laura Barisoni ◽  
H. William Schnaper ◽  
Jeffrey B. Kopp
Keyword(s):  
Current Knowledge ◽  
Diffuse Mesangial Sclerosis ◽  
Therapeutic Approaches ◽  
Glomerular Diseases ◽  
Podocyte Injury ◽  
Collapsing Glomerulopathy ◽  
Novel Approach ◽  
Genes Encoding ◽  
Glomerular Morphology

AbstractContext.—Etiologic factors and pathways leading to altered podocyte phenotype are clearly numerous and involve the activity of different cellular function.Objective.—To focus on recent discoveries in podocyte biology and genetics and their relevance to these human glomerular diseases, named podocytopathies.Data Sources.—Genetic mutations in genes encoding for proteins in the nucleus, slit diaphragm, podocyte cytoplasm, and cell membrane are responsible for podocyte phenotype and functional abnormalities. Podocyte injury may also derive from secondary stimuli, such as mechanical stress, infections, or use of certain medications. Podocytes can respond to injury in a limited number of ways, which include (1) effacement, (2) apoptosis, (3) arrest of development, and (4) dedifferentiation. Each of these pathways results in a specific glomerular morphology: minimal change nephropathy, focal segmental glomerulosclerosis, diffuse mesangial sclerosis, and collapsing glomerulopathy.Conclusions.—Based on current knowledge of podocyte biology, we organized etiologic factors and morphologic features in a taxonomy of podocytopathies, which provides a novel approach to the classification of these diseases. Current and experimental therapeutic approaches are also discussed.

Adenomyosis – its possible effect on endometrial function and receptivity

2021 ◽  
Vol 86 (3) ◽  
pp. 205-209
Author(s):  
Karel Crha ◽  
◽  
Michal Ješeta ◽  
Radovan Pilka ◽  
Pavel Ventruba ◽  
...  
Keyword(s):  
Epithelial Mesenchymal Transition ◽  
Current Knowledge ◽  
Histopathological Examination ◽  
Transvaginal Ultrasound ◽  
Embryo Implantation ◽  
Diagnostic Methods ◽  
Mesenchymal Transition ◽  
New Information

Summary Objective: There have been many studies on adenomyosis, which can impair the quality of life of a woman. There are various kinds of opinions on the pathogenesis, diagnostics and treatment of adenomyosis. The goal of this article is to present the current knowledge of adenomyosis and its impact on the endometrial function and receptivity. Methods: PubMed/Medline, Web of Sciences and Scopus were searched for the articles in English indexed until February 2021 with terms of: adenomyosis, endometrial receptivity, and infertility. Results: Recent studies on angiogenesis and epithelial-mesenchymal transition in the endometrium bring new information on the ethiology and pathogenesis of adenomyosis. In clinical practice, the main diagnostic methods of adenomyosis include transvaginal ultrasound, magnetic resonance imaging or hysteroscopy, although the definitive confirmation is set by histopathological examination. The rules of #Enzian classification of endometriosis should be applied for the classification of adenomyosis. The treatment of adenomyosis should consider individual clinical presentation and reproductive plans of a patient and should be performed in centers for the treatment of endometriosis. Conclusion: Adenomyosis affects endometrial vascularisation and epithelial-mesenchymal transition/mesenchymal-epithelial transition; thus, it can be the cause of irregular uterine bleeding or embryo implantation failure. The research and analysis of endometrial proteome could lead to the new ways of adenomyosis treatment.

scholarly journals Maser, infrared and optical emission for late-type stars in the Galactic plane

2017 ◽  
Vol 13 (S336) ◽  
pp. 184-186
Author(s):  
L. H. Quiroga-Nuñez ◽  
H. J. van Langevelde ◽  
L. O. Sjouwerman ◽  
Y. M. Pihlström ◽  
M. J. Reid ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Population Distribution ◽  
Massive Stars ◽  
Optical Emission ◽  
Proper Motions ◽  
Late Type ◽  
Intrinsic Properties ◽  
Radio Observations ◽  
Evolved Stars

AbstractRadio astrometric campaigns using VLBI have provided distances and proper motions for masers associated with young massive stars (BeSSeL survey). The ongoing BAaDE project plans to obtain astrometric information of SiO maser stars located in the inner Galaxy. These stars are associated with evolved, mass-losing stars. By overlapping optical (Gaia), infrared (2MASS, MSX and WISE) and radio (BAaDE) sources, we expect to obtain important clues on the intrinsic properties and population distribution of late-type stars. Moreover, a comparison of the Galactic parameters obtained with Gaia and VLBI can be done using radio observations on different targets: young massive stars (BeSSeL) and evolved stars (BAaDE).

scholarly journals Predictions of variable mass loss for Luminous Blue Variables

2002 ◽  
Vol 393 (2) ◽  
pp. 543-553 ◽  
Author(s):  
Jorick S. Vink ◽  
A. de Koter
Keyword(s):  
Mass Loss ◽  
Variable Mass ◽  
Luminous Blue Variables

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.

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