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).

scholarly journals Photospheric and “Chromospheric” CIV Lines in B-Main-Sequence Stars

1986 ◽  
Vol 116 ◽  
pp. 113-116
Author(s):  
Fiorella Castelli ◽  
Carlo Morossi ◽  
Roberto Stalio
Keyword(s):  
High Temperature ◽  
Stellar Wind ◽  
High Velocity ◽  
Main Sequence ◽  
Stellar Atmosphere ◽  
Uv Spectra ◽  
Spectral Lines ◽  
Early Type ◽  
Main Sequence Stars ◽  
Early Type Stars

The presence in the far-UV spectra of early-type stars of spectral lines of superionized atoms is argument of controversial debate among astronomers. Presently there is agreement on the non-radiative origin of these ions but not on the proposed mechanisms for their production nor on the proposed locations in the stellar atmosphere where they are abundant. Cassinelli et al. (1978) suggest that the Auger mechanism is operative in a cool wind blowing above a narrow corona to produce these ions; Lucy and White (1980) introduce radiative instabilities growing into hot blobs distributed across the stellar wind; Doazan and Thomas (1982) make these ions to be formed in both pre- and post-coronal, high temperature regions at low and high velocity respectively.

scholarly journals Empirical wind models from detail ed UV-line fits: Tau Scorpii

1981 ◽  
Vol 59 ◽  
pp. 161-165
Author(s):  
W.-R. Hamann
Keyword(s):  
Main Sequence ◽  
The Other ◽  
Line Formation ◽  
Early Type ◽  
Systematic Comparison ◽  
Early Type Stars ◽  
Sobolev Approximation

The main-sequence BO star Tau Sco has been studied previously by Lamers and Rogerson (1978). However, their line fit was restricted to the blue wings of the UV resonance lines because the line formation was calculated in Sobolev approximation. We now repeat this investigation by means of the comoving-frame (CMF) method, which we have extended to the treatment of overlapping doublets. From a systematic comparison (Hamann 1980b) we know that the results may deviate considerably from those of the Sobolev method. Our method has been applied previously to the other “prototype” of mass loosing early-type stars, the Of star Zeta Puppis (Hamann 1980a).

scholarly journals Resonance Line Profiles from Radial Accretion Flows

1988 ◽  
Vol 103 ◽  
pp. 127-128
Author(s):  
R. Tylenda
Keyword(s):  
Resonance Line ◽  
Compact Star ◽  
Stellar Winds ◽  
Line Formation ◽  
Line Profiles ◽  
Early Type ◽  
Principal Mechanism ◽  
Accretion Flows ◽  
Early Type Star ◽  
Early Type Stars

A compact star in a detached binary system can accrete the matter from the stellar wind of the companion. In this case a more or less radial accretion flow is formed. By analogy to stellar winds from early type stars it is usually believed that the accretion of this sort should produce inverse P-Cygni profiles in resonance lines. However, there are physical differences between the wind and the radial accretion which can alter the outgoing profile significantly.The matter outflowing from an early type star cools off very fast due to the adiabatic expansion. However, it remains highly ionized as the quickly decreasing density does not allow it to recombine. Therefore the principal mechanism for the resonance line formation here is the scattering of the stellar continuum photons in the wind.

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).

Change to the Demands Made of the Teaching Profession and the Ambiguity of New Concepts

2012 ◽  
Vol 2 (1) ◽  
pp. 7-18
Author(s):  
Jana Kohnová
Keyword(s):  
Teaching Profession ◽  
Further Education ◽  
Career Progression ◽  
Quality Of Education ◽  
Ministry Of Education ◽  
The Czech Republic ◽  
New Concepts ◽  
Educational Programmes ◽  
A Current

This paper is concerned with concepts such as quality of education, evaluation of the standard of the work of the teacher and comparison of educational results. It points to the importance of standards and the difficulties involved in their implementation. It also discusses the concept of competence and its relevance to framework educational programmes and the further education of teachers. The paper also focuses on a number of trends in education that are less widely discussed: instability — permanent change, reduction of education, emphasis on topicality and practical applicability, underestimation of the system, etc. The final part of the paper presents a current project from the Ministry of Education, Youth and Sport of the Czech Republic — a proposal for career progression.

Sergio Leone

2020 ◽  
Author(s):  
Christian Uva
Keyword(s):  
National Identity ◽  
Political Interest ◽  
Current Events ◽  
Classical Models ◽  
Key Aspects ◽  
Sergio Leone

Spectacle, myth, fable. These are the main categories that have traditionally defined Sergio Leone’s cinematic production, but it is necessary to underline how much they are fueled by a profound, layered political interest. Leone’s cinema bears witness to a critical outlook both on the subjects it showcases and on its representational means. Far from any militancy and escaping ideological classifications, Leone’s perspective is problematic and unreconciled: it is grounded in the coexistence of different elements in a state of perennial productive tension and instability. The adjective “political” takes on a deeper meaning when it is used to denote the director’s ability to narrate and interpret key aspects of Italian national identity and history. The abstract quality of his production relies on an original use of different genres, particularly sword-and-sandal and the Spaghetti Western, which allowed Leone to insert frequent symbolic references to both history and then-current events. On the stylistic level, his constant disobedience to classical models and his need to revolutionize forms were motivated by an authorial desire to make films politically, though still within a conception of cinema as an industrial spectacle.

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.

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