Some results of the Barbier-Chalonge-Divan system of stellar classification

1966 ◽  
Vol 24 ◽  
pp. 77-90 ◽  
Author(s):  
D. Chalonge
Keyword(s):  
Early Type ◽  
Parameter System ◽  
Early Type Stars ◽  
Two Parameter

Several years ago a three-parameter system of stellar classification has been proposed (1, 2), for the early-type stars (O-G): it was an improvement on the two-parameter system described by Barbier and Chalonge (3).

scholarly journals Singly-Ionized Iron Emission Lines in the Spectra of Early Type Stars

1976 ◽  
Vol 70 ◽  
pp. 99-103
Author(s):  
R. Viotti ◽  
P. Koubský
Keyword(s):  
Spectroscopic Investigation ◽  
Emission Lines ◽  
Be Stars ◽  
Early Type ◽  
Atomic Processes ◽  
Early Type Stars ◽  
Stellar Envelopes ◽  
Two Parameter

The appearance of singly ionized iron emission lines in the spectra of early type stars is studied, and the results of a spectroscopic investigation of EW Lac and other Be stars are given. We also discuss the atomic processes of excitation of Fe ii in the stellar envelopes using a two-parameter diagram W, NeT−1/2e.

Radio Continuum Measurements of Southern Early‐Type Stars. III. Nonthermal Emission from Wolf‐Rayet Stars

1999 ◽  
Vol 518 (2) ◽  
pp. 890-900 ◽  
Author(s):  
Jessica M. Chapman ◽  
Claus Leitherer ◽  
Barbel Koribalski ◽  
Roderick Bouter ◽  
Michelle Storey
Keyword(s):  
Radio Continuum ◽  
Early Type ◽  
Nonthermal Emission ◽  
Early Type Stars

Preliminary Observations of Interstellar Sodium D-Line Absorption towards the Carina Nebula

1980 ◽  
Vol 4 (1) ◽  
pp. 95-97 ◽  
Author(s):  
J. B. Whiteoak ◽  
F. F. Gardner
Keyword(s):  
High Resolution ◽  
Hii Regions ◽  
Early Type ◽  
Interstellar Clouds ◽  
Carina Nebula ◽  
Line Absorption ◽  
General Investigation ◽  
Early Type Stars ◽  
Resolution Study

As part of a general investigation of interstellar clouds associated with southern HII regions we have begun a high-resolution study of the sodium D-line absorption in the directions of early-type stars that are likely to be associated with or located behind the clouds.

scholarly journals Chemical Abundances of Early Type Stars

1998 ◽  
Vol 188 ◽  
pp. 224-225
Author(s):  
S. Tanaka ◽  
S. Kitamoto ◽  
T. Suzuki ◽  
K. Torii ◽  
M.F. Corcoran ◽  
...  
Keyword(s):  
Surface Layer ◽  
Stellar Wind ◽  
Nuclear Reactions ◽  
X Rays ◽  
Early Type ◽  
Chemical Abundances ◽  
X Ray ◽  
Low Metallicity ◽  
Early Type Stars

X-rays from early-type stars are emitted by the corona or the stellar wind. The materials in the surface layer of early-type stars are not contaminated by nuclear reactions in the stellar inside. Therefore, abundance study of the early-type stars provides us an information of the abundances of the original gas. However, the X-ray observations indicate low-metallicity, which is about 0.3 times of cosmic abundances. This fact raises the problem on the cosmic abundances.

scholarly journals UV Spectral Classification of B Stars

1985 ◽  
Vol 111 ◽  
pp. 411-413
Author(s):  
Janet Rountree ◽  
George Sonneborn ◽  
Robert J. Panek
Keyword(s):  
Classification System ◽  
Classification Criteria ◽  
High Dispersion ◽  
Spectral Classification ◽  
Early Type ◽  
B Stars ◽  
Dimensional Classification ◽  
Early Type Stars ◽  
Comprehensive Classification

Previous studies of ultraviolet spectral classification have been insufficient to establish a comprehensive classification system for ultraviolet spectra of early-type stars because of inadequate spectral resolution. We have initiated a new study of ultraviolet spectral classification of B stars using high-dispersion IUE archival data. High-dispersion SWP spectra of MK standards and other B stars are retrieved from the IUE archives and numerically degraded to a uniform resolution of 0.25 or 0.50 Å. The spectra (in the form of plots or photowrites) are then visually examined with the aim of setting up a two-dimensional classification matrix. We follow the method used to create the MK classification system for visual spectra. The purpose of this work is to examine the applicability of the MK system (and in particular, the set of standard stars) in the ultraviolet, and to establish classification criteria in this spectral region.

scholarly journals The Use of Model Atmospheres for Temperature-Gravity Calibration

1973 ◽  
Vol 54 ◽  
pp. 173-221
Author(s):  
J. C. Pecker
Keyword(s):  
Model Building ◽  
Stellar Atmosphere ◽  
Line Formation ◽  
Early Type ◽  
New Concepts ◽  
Total Luminosity ◽  
Classical Models ◽  
Early Type Stars ◽  
Two Parameters

Regardless of the degree of elaboration of series of models, just how can they be used for calibration purposes? And how much is this calibration sensitive to the quality of the model theory? These two questions are the basis of our discussion, which covers : I – The general principles of the use of model atmospheres in stellar calibration (1 – The two dimensional classifications; 2 – The use of the total luminosity; 3 – The cases of Vega and Sirius; 4 – The calibration of ST – Teff relation); II – The failures of the two parameters model atmospheres (1 – The observational need for more-than-two-parameters classification; 2 – The abundance of elements, the line formation, and the model atmospheres; 3 – Various sources of unadequacy of models; 4 – Envelopes or shell features; their influence on model-building; 5 – The case of HD 45677. Diagnostic of early-type stars; 6 – Various unexplained spectral features); III – The present state of the model factory (1 – The classical models; 2 – New concepts in the description of a stellar atmosphere; 3 – New approaches in model making; 4 – Conclusions).

X‐Ray Emission from Early‐Type Stars in the Orion Nebula Cluster

2005 ◽  
Vol 160 (2) ◽  
pp. 557-581 ◽  
Author(s):  
B. Stelzer ◽  
E. Flaccomio ◽  
T. Montmerle ◽  
G. Micela ◽  
S. Sciortino ◽  
...  
Keyword(s):  
Orion Nebula ◽  
Early Type ◽  
X Ray ◽  
Early Type Stars

scholarly journals Torsional oscillations and observed rotational period variations in early-type stars

2016 ◽  
Vol 464 (1) ◽  
pp. 933-939 ◽  
Author(s):  
J. Krtička ◽  
Z. Mikulášek ◽  
G. W. Henry ◽  
P. Kurfürst ◽  
M. Karlický
Keyword(s):  
Rotational Period ◽  
Early Type ◽  
Torsional Oscillations ◽  
Period Variations ◽  
Early Type Stars

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 New Results on Pulsating OB Stars

1995 ◽  
Vol 155 ◽  
pp. 44-55 ◽  
Author(s):  
Paweł Moskalik
Keyword(s):  
Data Model ◽  
Physical Mechanism ◽  
High Order ◽  
Early Type ◽  
Instability Strip ◽  
Model Calculations ◽  
B Stars ◽  
Ob Stars ◽  
Early Type Stars ◽  
Theoretical Results

AbstractUntil very recently the physical mechanism driving oscillations in β Cep and other early type stars has been a mystery. The breakthrough came with the publication of new OPAL and OP opacity data. Model calculations with the new opacities have demonstrated that the pulsations are driven by the familiar K-mechanism, acting in the metal opacity bump at T ≈ 2 × 105K. The mechanism excites the low order p- and g-modes in the upper part of the instability strip and the high order g-modes in the lower part of the strip. The theoretical instability domains agree well with the observed domains of the β Cep and the SPB stars. In this review I present these recent theoretical results and discuss their consequences for our understanding of B stars pulsations.

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