D. The Line Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 207-244
Author(s):  
R. P. Kraft
Keyword(s):  
Variable Stars ◽  
The Other ◽  
Line Spectrum ◽  
Afternoon Session ◽  
Empirical Information ◽  
Pulsating Variable Stars ◽  
Almost Continuous ◽  
Informal Approach

(Ed. note:Encouraged by the success of the more informal approach in Christy's presentation, we tried an even more extreme experiment in this session, I-D. In essence, Kraft held the floor continuously all morning, and for the hour and a half afternoon session, serving as a combined Summary-Introductory speaker and a marathon-moderator of a running discussion on the line spectrum of cepheids. There was almost continuous interruption of his presentation; and most points raised from the floor were followed through in detail, no matter how digressive to the main presentation. This approach turned out to be much too extreme. It is wearing on the speaker, and the other members of the symposium feel more like an audience and less like participants in a dissective discussion. Because Kraft presented a compendious collection of empirical information, and, based on it, an exceedingly novel series of suggestions on the cepheid problem, these defects were probably aggravated by the first and alleviated by the second. I am much indebted to Kraft for working with me on a preliminary editing, to try to delete the side-excursions and to retain coherence about the main points. As usual, however, all responsibility for defects in final editing is wholly my own.)

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

scholarly journals The Effect of Convection in Nonlinear One-Zone Stellar Models

1993 ◽  
Vol 134 ◽  
pp. 355-358
Author(s):  
M. Saitou
Keyword(s):  
Limit Cycle ◽  
Chaotic Behavior ◽  
Period Doubling ◽  
Variable Stars ◽  
Period Doubling Bifurcation ◽  
The Other ◽  
Other Hand ◽  
Pulsating Variable Stars ◽  
Stellar Models

AbstractWe study the convective nonlinear one-zone models of the pulsating variable stars. In the small convective case, the solution shows chaotic behavior through the period doubling bifurcation as the temperature is lower although the temperature at which the chaos appears is lower than in the case of no convection. On the other hand, in the strong convective case, the solution only shows period-one limit cycle.

B. The Non-Linear Calculations for Pulsating Stars

1967 ◽  
Vol 28 ◽  
pp. 105-176
Author(s):  
Robert F. Christy
Keyword(s):  
Major Part ◽  
Afternoon Session ◽  
Discussion Session ◽  
Pulsating Stars ◽  
Fourth Symposium ◽  
Non Linear ◽  
Considerable Discussion ◽  
Informal Approach ◽  
Preceding Session

(Ed. note: The custom in these Symposia has been to have a summary-introductory presentation which lasts about 1 to 1.5 hours, during which discussion from the floor is minor and usually directed at technical clarification. The remainder of the session is then devoted to discussion of the whole subject, oriented around the summary-introduction. The preceding session, I-A, at Nice, followed this pattern. Christy suggested that we might experiment in his presentation with a much more informal approach, allowing considerable discussion of the points raised in the summary-introduction during its presentation, with perhaps the entire morning spent in this way, reserving the afternoon session for discussion only. At Varenna, in the Fourth Symposium, several of the summaryintroductory papers presented from the astronomical viewpoint had been so full of concepts unfamiliar to a number of the aerodynamicists-physicists present, that a major part of the following discussion session had been devoted to simply clarifying concepts and then repeating a considerable amount of what had been summarized. So, always looking for alternatives which help to increase the understanding between the different disciplines by introducing clarification of concept as expeditiously as possible, we tried Christy's suggestion. Thus you will find the pattern of the following different from that in session I-A. I am much indebted to Christy for extensive collaboration in editing the resulting combined presentation and discussion. As always, however, I have taken upon myself the responsibility for the final editing, and so all shortcomings are on my head.)

Biomineralization Processes

1989 ◽  
Author(s):  
Heinz A. Lowenstam ◽  
Stephen Weiner
Keyword(s):  
Continuous Spectrum ◽  
Convergent Evolution ◽  
Common Ancestor ◽  
External Medium ◽  
The Other ◽  
Mineral Formation ◽  
Mineralization Processes ◽  
Established Fact ◽  
Different Sources ◽  
Almost Continuous

The large number of different minerals formed by organisms from almost 50 different phyla described in Chapter 2 should in itself discourage anyone from searching for the mechanism of biomineralization. On the other hand, the survey of macromolecules used by many organisms to control mineralization (Chapter 2), even though limited primarily to carbonate- and phosphate-bearing mineralized hard parts, shows that similar and rather unusual acidic glycoproteins and proteoglycans are widely utilized in biomineralization. This raises the possibility that many organisms may have adopted common approaches or strategies for regulating mineral formation. We do not know whether this arose as a result of divergence from a common ancestor or is a product of convergent evolution in which many different phyla independently began utilizing similar macromolecules for controlling mineralization (see Chapter 12). Either way we view the diversity in biomineralization as the product of a very broad and almost continuous spectrum of processes that organisms use to control mineralization. This ranges from no apparent control at one end to, it seems, control over every detail at the other. However, this is achieved by a fairly limited number of different basic processes used in various combinations and ways to produce a unique final product. This last statement is, we readily admit at this point in time, more an act of faith than an established fact. In this chapter we will try to identify and/or speculate about some of these basic processes. We will draw upon material from many different sources, and, in particular, we will refer whenever possible to the more detailed descriptions of mineralization processes given in the chapters that follow. As a consequence, this chapter may also be used by the reader as a guide toward more discriminating reading on selected topics in the remainder of the book. The spectrum of biomineralization processes can in principle be easily divided into cases in which control is exercised in some way over mineralization and those in which it is not. In practice the differentiation is not that simple as all organisms do exercise some control at one level or another, even if it simply involves, for example, removing from the cell some undesirable metabolic end-product or ion that combines with another ion in the external medium and precipitates.

scholarly journals The Population of Pulsating Variable Stars in the Sextans Dwarf Spheroidal Galaxy

2019 ◽  
Vol 157 (1) ◽  
pp. 35 ◽  
Author(s):  
A. Katherina Vivas ◽  
Javier Alonso-García ◽  
Mario Mateo ◽  
Alistair Walker ◽  
Brittany Howard
Keyword(s):  
Variable Stars ◽  
Pulsating Variable Stars

scholarly journals New results on OGLE Cepheids and PL relations in the LMC and SMC

2004 ◽  
Vol 193 ◽  
pp. 75-82
Author(s):  
A. Udalski
Keyword(s):  
Gravitational Lensing ◽  
Variable Stars ◽  
Magellanic Clouds ◽  
Photometric Data ◽  
Second Phase ◽  
Internet Archive ◽  
Pulsating Stars ◽  
Third Phase ◽  
Pulsating Variable Stars ◽  
Star Field

AbstractWe present results of the search for pulsating variable stars in the Magellanic Cloud fields covering central parts of these galaxies. The data were collected during the second phase of the Optical Gravitational Lensing Experiment survey (OGLE-II) from 1997 to 2000. In total, several thousand pulsating stars (Cepheids, RR Lyr) were found in both Magellanic Clouds. The photometric data of all objects are available to the astronomical community from the OGLE Internet archive. We present basic properties of pulsating stars in the Magellanic Clouds including Period–Luminosity relations for Cepheids. We also discuss observational prospects for the pulsating star field in the ongoing third phase of the OGLE project (OGLE-III) which started in 2001.

scholarly journals Phase-night diagram for periodic variable stars

1986 ◽  
Vol 118 ◽  
pp. 297-298
Author(s):  
Z. Kvíz
Keyword(s):  
Variable Stars ◽  
The Other ◽  
Graphical Form ◽  
Continuous Observation ◽  
Hewlett Packard ◽  
The World

A program has been developed for the Hewlett-Packard Computer 9845 to represent in a graphical form the period of observability, for individual nights, of periodic phenomena of stars with respect to the phase. One version of the program (Fig. 1) gives the observability with respect to the phase for the whole year. The other version (Fig. 2) gives the beginning and end of the suitable observing interval for several observatories around the world thus facilitating preparation of a program for 24-hour continuous observation.

scholarly journals Luminous vapour from the mercury arc and the progressive changes in its spectrum

1925 ◽  
Vol 108 (746) ◽  
pp. 262-279 ◽  
Keyword(s):  
Glow Discharge ◽  
Electric Field ◽  
Arc Discharge ◽  
The Other ◽  
Line Spectrum ◽  
Mercury Vapour ◽  
Band Spectrum ◽  
Other Hand ◽  
Continuous Band

It was observed originally by Stark that a stream of mercury vapour allowed to distil away from the arc or glow discharge in vacuo remains luminous. It may be said to carry the luminosity away with it, and in the case of the arc discharge there is no difficulty in detecting the luminosity for 50 cm. or so from the source. Stark found that when a glow discharge was used, which developed the continuous band spectrum, this spectrum could be detected in the distilled vapour, along with the line spectrum. When the glow was passed through an electric field, the line spectrum was found to be quenched, leaving the band spectrum unaffected. The arc discharge, on the other hand, gave only the line spectrum in his experiments.

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