The ZZ Ceti Stars and the Rate of Evolution of White Dwarfs

1980 ◽  
Vol 58 ◽  
pp. 613-620
Author(s):  
Edward L. Robinson ◽  
S. O. Kepler
Keyword(s):  
Stellar Evolution ◽  
Light Curves ◽  
The Other ◽  
Pulsating Stars ◽  
Relative Value ◽  
Stellar Pulsations ◽  
Additional Mode ◽  
Stellar Interiors ◽  
The One ◽  
Multi Mode

The importance of the ZZ Ceti stars, and indeed the importance of all pulsating stars, derives from the fact that stellar pulsations probe the interiors of stars, and thus they test directly our models of stellar interiors and stellar evolution. The relative value of stellar pulsations as such a probe depends on, among other factors, the number of pulsation modes simultaneously excited in a star, as each additional mode depends on and constrains the properties of the star in a different way. Judged by this criterion, the pulsations of the ZZ Ceti stars should be unusually valuable because all ZZ Ceti stars are multi-mode variables. For example, among the ZZ Ceti stars with well studied light curves, the one with the fewest modes is R548 (= ZZ Ceti itself) with 4 pulsation modes simultaneously excited (Robinson et al. 1976), while some of the other ZZ Ceti stars can have dozens of pulsation modes simutaneously excited (cf. Robinson 1979).

Lessing's Treatment of the Story of the Ring, and its Teaching

PMLA ◽  
1901 ◽  
Vol 16 (1) ◽  
pp. 107-116
Author(s):  
W. H. Carruth
Keyword(s):  
Decision Making ◽  
The Other ◽  
Outward Appearance ◽  
Final Version ◽  
Good Works ◽  
Relative Value ◽  
Healing Power ◽  
Divine Origin ◽  
The One ◽  
Point Of Departure

In Westermann's Monatshefte for January, 1891, and later in his ‘Life of Lessing,‘ Professor Erich Schmidt has outlined the chief features of the history and transformations of the story of the three rings in Europe. On examination it will be found that all the versions of the story belong to one or the other of two types, which are represented by the two earliest forms of the story preserved to us. The oldest version, that of the Spanish Jew Salomo ben Verga, tells of two rings or jewels only, which were in outward appearance exactly alike, and there is no question of one being genuine and the other false, but only of the relative value of the two. In the absence of the father it is found impossible to decide the question, and thus the decision between Christianity and Judaism is simply avoided. In Li Dis dou vrai aniel, a French poem of the end of the twelfth century, three rings appear, and to the original or genuine ring is attributed a marvelous healing power by which it may be recognized, and following which a decision is arrived at among the three religions, in this case in favor of Christianity, although ther were not wanting later narrators so bold as to hint that the true ring was possessed by Judaism. The version of Etienne de Bourbon, the versions of the Cento Novelle, the three versions of the Gesta Romanorum, all belong to one or the other of two types. We may refer to these two types as the Spanish type and the French type. Those of the first type, to which belongs also the version of Boccaccio, the one from which Lessing took his point of departure, avoid a decision, implying that all religions are equally authoritative, but without inherent or inner evidence of their quality. Those of the second type, to which in many of its features Lessing's final version of the story is allied, lead to a decision, making religion of divine origin indeed, but supplying a test, that of good works, whereby the true religion may be recognized.

scholarly journals The occurrence of non-pulsating stars in the γ Dor and δ Sct instability regions

2013 ◽  
Vol 9 (S301) ◽  
pp. 63-66 ◽  
Author(s):  
Joyce A. Guzik ◽  
Paul A. Bradley ◽  
Jason Jackiewicz ◽  
Katrien Uytterhoeven ◽  
Karen Kinemuchi
Keyword(s):  
Effective Temperature ◽  
Power Spectra ◽  
Light Curves ◽  
The Other ◽  
Pulsating Stars ◽  
Driving Mechanisms ◽  
Other Hand ◽  
Instability Regions ◽  
Physical Reasons ◽  
Ppm Level

AbstractWe examine the light curves of over 2700 stars observed in long cadence by the Kepler spacecraft as part of the Guest Observer program. Most of these stars are faint (Kepler magnitude > 14), and fall near or within the effective temperature and log g range of the γ Dor and δ Sct instability strips. We find that the pulsating stars are obvious from inspection of the light curves and power spectra, even for these faint stars. However, we find that a large number of stars are ‘constant’, i.e. show no frequencies in the 0.2 to 24 d−1 range above the 20 ppm level. We discuss the statistics for the constant stars, and some possible physical reasons for lack of pulsations. On the other hand, γ Dor and δ Sct candidates have been found in the Kepler data spread throughout and even outside of the instability regions of both types that were established from pre-Kepler ground-based observations. We revisit mechanisms to produce g- or p-mode pulsations in conditions when these modes are not expected to be unstable via the He-ionization κ effect (δ Sct) or convective blocking (γ Dor) pulsation driving mechanisms.

scholarly journals ω Centauri – a Laboratory for Critical Tests of Stellar Structure and Evolution

2000 ◽  
Vol 176 ◽  
pp. 252-253
Author(s):  
L. M. Freyhammer ◽  
J. O. Petersen ◽  
M. I. Andersen
Keyword(s):  
Stellar Evolution ◽  
Monitoring Program ◽  
Light Curves ◽  
Stellar Structure ◽  
Preliminary Results ◽  
Test Models ◽  
Multi Mode

AbstractPreliminary results are reported for a monitoring program on ω Cen. We search for multi-mode SX Phe stars and changes in pulsation parameters of the cluster variables in order to test models of stellar evolution. With a periodogram for 10,000 light curves, we estimate that ω Cen hosts several hundred SX Phe stars.

scholarly journals Light Curve Analysis of Long Period Pulsating Stars with the Wavelet Method: The semiregular star V Boo

1995 ◽  
Vol 155 ◽  
pp. 417-418 ◽  
Author(s):  
K. Szatmáry ◽  
J. Gál ◽  
L. L. Kiss
Keyword(s):  
Stellar Evolution ◽  
Curve Analysis ◽  
Point Of View ◽  
Light Curves ◽  
Data Series ◽  
Strong Fluctuation ◽  
Light Curve Analysis ◽  
Pulsating Stars ◽  
Long Period ◽  
Data Banks

AbstractWe have collected long data series of some SR and Mira stars from data banks. In many cases the light curves show strong fluctuation or variation in the period, phase and amplitude. The detection of the significant changes of these parameters is important from the point of view of pulsation theory and stellar evolution. We present here the analysis of V Boo. The used method is the Fourier and wavelet analysis in order to point out the modulations in the frequency and amplitude.

Aristippus of Cyrene

2020 ◽  
pp. 380-411
Author(s):  
Voula Tsouna
Keyword(s):  
Strong Evidence ◽  
Crucial Role ◽  
Ethical Conduct ◽  
The Other ◽  
Philosophical Inquiry ◽  
Ethical Implications ◽  
Relative Value ◽  
The One ◽  
The City

“Aristippus of Cyrene” re-evaluates the evidence concerning, on the one hand, Aristippus’ alleged hedonism and, on the other, his affiliation with Socrates and the Socratic circle. The central thesis of the chapter is this: even though some sources attribute to Aristippus the sort of ethical hedonism that we know to have been held by his grandson (Aristippus the Younger), there is strong evidence that in fact Aristippus of Cyrene was not an ethical hedonist but endorsed Socratic concerns and values. These latter include philosophical inquiry focused on ethics, the paramount importance of philosophy for education and the care of one’s soul, concern to develop the virtues and assess the relative value of external goods, the crucial role of reason and prudence in ethical conduct, the ethical implications of systematically pursuing pleasure and avoiding pain, and the rationalism that should determine one’s attitudes toward relatives, acquaintances, fellow-citizens, and the city itself.

Research into Practice: Using Money to Teach about the Decimal System

1988 ◽  
Vol 36 (4) ◽  
pp. 42-43
Author(s):  
Analúcia Dias Schliemann
Keyword(s):  
Everyday Life ◽  
The Other ◽  
Arithmetic Operations ◽  
Decimal System ◽  
Absolute Value ◽  
Number Words ◽  
Other Hand ◽  
Relative Value ◽  
The One ◽  
Value Decomposition

Children learn much mathematics in everyday life. When they buy things, for example, they have to count their money and calculate their change. Counting money is a special type of counting. On the one hand, when children count objects, they establish a one-to-one correspondence bet ween objects and number words; only absolute value, as opposed to relative value, is involved. On the other hand, when counting money children must bear in mind both types of value; while they deal with the coins one by one (absolute value), they must also take into account the relative value of the coins. Counting money thus helps children understand the decomposition of numbers; a large amount (for example, sixty-eight) is made up of smaller amounts—tens and ones—that can be repeated (six tens and eight one). All these ideas—relative and absolute value, decomposition, and repetition of equal values—are basic both to the understanding of the decimal system and to the undertanding of important properties of arithmetic operations.

An innovative four-layer heuristic for scheduling multi-mode projects under multiple resource constrains

2019 ◽  
Vol 53 (4) ◽  
pp. 1309-1330
Author(s):  
Reza Zamani
Keyword(s):  
Resource Constraints ◽  
Solution Space ◽  
Sampling Technique ◽  
Search Space ◽  
The Other ◽  
Evolutionary Search ◽  
Search Mechanism ◽  
The One ◽  
Multiple Resource ◽  
Multi Mode

In this paper, an innovative four-layer heuristic is presented for scheduling multi-mode projects under multiple resource constraints. For this purpose, a biased-random sampling technique, a local search, a decomposition method, and an evolutionary search mechanism, each in a separate layer, are combined, with each layer passing its output to the next layer for improvement. The procedure has been designed based on the fact that what makes the scheduling of multi-mode projects hard to solve is a massive search space of modes compounded with the starting times of activities. That is why the procedure is aimed at balancing exploration versus exploitation in searching a massive search space. On the one hand, it exploits promising areas further and, on the other hand, it searches unexplored areas for expanding its range. Since the first layer provides an initial solution, and each of the other three layers can either improve the result of its previous layer or keep it unchanged, solutions never deteriorate and hence promising areas are exploited. Moreover, unexplored areas are searched effectively because each layer explores solution space differently than its previous layer. Based on whether or not an improvement each layer can make to the result of its previous layer, the effect of the corresponding layer on the performance of the procedure has been measured.

scholarly journals Cepheid period changes and stellar evolution

1984 ◽  
Vol 105 ◽  
pp. 441-444 ◽  
Author(s):  
J.D. Fernie
Keyword(s):  
Stellar Evolution ◽  
The Other ◽  
Other Hand ◽  
Evolutionary Changes ◽  
Classical Cepheids ◽  
The One ◽  
Hr Diagram

The question of whether or not the period changes observed in some classical cepheids are due to evolution across the HR diagram remains controversial. On the one hand, it is known that the stars are indeed evolving across the diagram and are therefore changing their radii and must therefore be changing their periods. On the other hand, only a fraction of cepheids appear to have period changes, and some of these seem to be in the form of sudden jumps. Is it then that the evolutionary changes are too small to be detected, and the observed changes due to something else? This note explores the question.

scholarly journals History of International Law Since the Peace of Westphalia

1912 ◽  
Vol 6 (1) ◽  
pp. 30-69 ◽  
Author(s):  
Amos S. Hershey
Keyword(s):  
International Law ◽  
French Revolution ◽  
Public Law ◽  
The Other ◽  
Relative Value ◽  
The World ◽  
History Of ◽  
Main Factors ◽  
History Of International Law ◽  
The One

The treaties of Münster and Osnabrück gave to Europe a sort of international constitution which remained the basis of its public law down to the French Revolution. But it would be a serious error to assume that the international community of states as revealed to the world by the Peace of Westphalia implied the recognition of the science of international law as understood and practiced by the society of nations at the present time. The science of international law as it exists today is a result of slow historical growth and is the product of two main factors, viz., certain theories or principles on the one hand, and international practice or custom on the other. The relative value and influence of the contributions of each of these factors is so difficult to determine that they have never been thoroughly eifted or separated — a task left for the future historians of international law.

scholarly journals Modulated Light Curves of Multiperiodic Stars

2011 ◽  
Vol 7 (S285) ◽  
pp. 286-288
Author(s):  
József M. Benkő ◽  
Róbert Szabó ◽  
Margit Paparó
Keyword(s):  
Light Curves ◽  
The Other ◽  
Pulsating Stars ◽  
Long Period ◽  
Blazhko Effect ◽  
Frequency Modulations ◽  
Modulated Light

AbstractWe modelled the light curves of modulated multiperiodically pulsating stars by a simple double-mode pulsation with combined amplitude and frequency modulations. The synthetic light curves and their spectra show similar features to those we found and discussed for monoperiodic stars. Comparing the synthetic light curves and their spectra with the observed ones helps us to classify the modulations and to distinguish between long-period modulation (Blazhko effect) and the other types of amplitude and/or period changes.

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