scholarly journals Delta Scuti Stars and Dwarf Cepheids: Review and Pulsation Modes

1980 ◽  
Vol 58 ◽  
pp. 361-370
Author(s):  
Michel Breger
Keyword(s):  
Variable Stars ◽  
Considerable Progress ◽  
Instability Strip ◽  
Individual Variable ◽  
Recent Developments ◽  
Delta Scuti ◽  
Scuti Stars ◽  
Made In

AbstractRecent developments in the field of Delta Scuti stars are discussed. Considerable progress has been made in determining the multiple-period structure of individual variable stars and in identifying the excited radial and nonradial modes through a variety of methods. This allows an analysis of the change of excited modes as a function of the position in the instability strip.

scholarly journals Frequency Oscillations in the Delta Scuti Star V534 Tauri: Preliminary Results of the STEPHI IX Campaign

2000 ◽  
Vol 176 ◽  
pp. 477-478
Author(s):  
L. Fox Machado ◽  
Z. P. Li ◽  
E. Michel ◽  
M. Alvarez ◽  
M. M. Hernández ◽  
...  
Keyword(s):  
Main Sequence ◽  
Class Iii ◽  
Significant Progress ◽  
Instability Strip ◽  
Preliminary Results ◽  
Scuti Star ◽  
Delta Scuti Star ◽  
Delta Scuti ◽  
Scuti Stars ◽  
Made In

The δ Scuti stars are pulsating variables located in the lower part of the Cepheid instability strip with spectral types from A2 to F0 on the main sequence, and from A3 to F5 at luminosity class III. These variables show short periods (< 0.3day) and luminosity amplitudes ranging from a few thousandths of a magnitude to several tenths. Over the last few years, significant progress has been made in the detection of pulsating modes in the framework of the multisite campaigns, e.g. STACC (Frandsen et al. 1996), DSN (Breger et al. 1998), STEPHI (Michel et al. 2000). For the 1998 STEPHI IX photometry campaign, the δ Scuti star V534 Tau of the Pleiades cluster (see Table 1) was monitored during a three week, three continent run. Preliminary results are reported here.

scholarly journals Astrophysical Applications of Delta Scuti Stars

1995 ◽  
Vol 155 ◽  
pp. 70-80
Author(s):  
Michel Breger
Keyword(s):  
Main Sequence ◽  
Statistical Significance ◽  
Instability Strip ◽  
Short Period ◽  
Scuti Star ◽  
Systematic Behaviour ◽  
Delta Scuti ◽  
F Stars ◽  
Available Information ◽  
Scuti Stars

AbstractThe δ Scuti stars pulsate with a large number of low-order radial and nonradial p-modes. There also exists some evidence for the presence of g-modes.The pulsational variability outside the classical δ Scuti star instability strip (A1V - F0V on the main sequence) is examined. New measurements do not confirm the short-period variability of the hot B9p star ET And. However, a number of cool, early-F stars shows variability around one day: the γ Dor variables. An explanation involving nonradial g modes appears the most promising.An examination of available information on the multi-periodicity of δ Scuti stars shows no systematic behaviour in which pulsation modes axe excited to an observable level with luminosity and temperature. The asteroseismological potential of δ Scuti vaxiables is briefly examined.So far, the period changes of five luminous Pop. I δ Scuti variables have been studied. While stellar evolution predicts period increases, decreases have been observed and reported for all five stars. The statistical significance of this result and alternative explanations axe briefly examined.

scholarly journals Delta Scuti Stars in Open Clusters: w2 and w20 in NGC 2264 and h501 and h906 in α Per

2000 ◽  
Vol 176 ◽  
pp. 465-466
Author(s):  
J. H. Peña ◽  
R. Peniche ◽  
F. Cervantes ◽  
R. M. García ◽  
J. P. Sareyan
Keyword(s):  
Chemical Composition ◽  
Effective Temperature ◽  
Variable Stars ◽  
Open Clusters ◽  
Early Type ◽  
Early Type Stars ◽  
Delta Scuti ◽  
Scuti Stars ◽  
Δ Scuti Stars

There are many advantages to studying variable stars in open clusters; the parameters that determine the evolution of the stars, such as chemical composition and age, can be considered to be the same for all the stars in the cluster. These data, along with the mass, effective temperature and superficial gravity, allow us to better determine the physics which explain the pulsation mechanisms. In the present paper the variable stars h501 and h906 in α Per and w2 and w20 in NGC 2264 are studied. In particular, the reasons why δ Scuti stars coexist with early type stars in NGC 2264 is examined.

Biological Production of (S)-acetoin: A State-of-the-Art Review

2019 ◽  
Vol 19 (25) ◽  
pp. 2348-2356 ◽  
Author(s):  
Neng-Zhong Xie ◽  
Jian-Xiu Li ◽  
Ri-Bo Huang
Keyword(s):  
Side Effects ◽  
Chemical Synthesis ◽  
State Of The Art ◽  
Optically Active ◽  
Considerable Progress ◽  
Future Prospects ◽  
Chiral Compound ◽  
Biological Production ◽  
Acetoin Production ◽  
Made In

Acetoin is an important four-carbon compound that has many applications in foods, chemical synthesis, cosmetics, cigarettes, soaps, and detergents. Its stereoisomer (S)-acetoin, a high-value chiral compound, can also be used to synthesize optically active drugs, which could enhance targeting properties and reduce side effects. Recently, considerable progress has been made in the development of biotechnological routes for (S)-acetoin production. In this review, various strategies for biological (S)- acetoin production are summarized, and their constraints and possible solutions are described. Furthermore, future prospects of biological production of (S)-acetoin are discussed.

scholarly journals III. On the nature and construction of the sun and fixed stars

1795 ◽  
Vol 85 ◽  
pp. 46-72 ◽  
Keyword(s):  
Central Body ◽  
Planetary System ◽  
Considerable Progress ◽  
The Sun ◽  
Great Satisfaction ◽  
The Earth ◽  
The World ◽  
Celestial Bodies ◽  
The Universe ◽  
Made In

Among the celestial bodies the sun is certainly the first which should attract our notice. It is a fountain of light that illuminates the world! it is the cause of that heat which main­tains the productive power of nature, and makes the earth a fit habitation for man! it is the central body of the planetary system; and what renders a knowledge of its nature still more interesting to us is, that the numberless stars which compose the universe, appear, by the strictest analogy, to be similar bodies. Their innate light is so intense, that it reaches the eye of the observer from the remotest regions of space, and forcibly claims his notice. Now, if we are convinced that an inquiry into the nature and properties of the sun is highly worthy of our notice, we may also with great satisfaction reflect on the considerable progress that has already been made in our knowledge of this eminent body. It would require a long detail to enumerate all the various discoveries which have been made on this subject; I shall, therefore, content myself with giving only the most capital of them.

The study of short orbital period of delta scuti pulsating variable stars

2019 ◽  
Vol 15 (S356) ◽  
pp. 407-407
Author(s):  
Abduselam Mohammed
Keyword(s):  
Time Delay ◽  
Orbital Period ◽  
Binary Stars ◽  
Arrival Time ◽  
Periodic Variation ◽  
Variable Stars ◽  
Orbital Elements ◽  
Pulsating Stars ◽  
Delta Scuti ◽  
Arrival Time Delay

AbstractAs a pulsating star moves in its binary orbit, the path length of the light between us and the star varies, leading to the periodic variation in the arrival time of the signal from the star to us (earth). With the consideration of pulsators light arrival time delay effects several new methods which allows using Kepler photometric data (light curves) alone to find binary stars have been recently developed. Among these modern techniques we used binarogram method and we identified that several δSct pulsating stars have companions. The application of these method on detecting long periods(i.e. longer than about 50 d) δSct pulsating stars is not new, but the uniqueness of this study is we verified that it is also applicable to detect and determine the orbital elements of short periods (i.e short orbital period) δSct pulsating stars. With this investigation, we identified the possible way to overcome effects of fictious peaks, even, on the maximum peaks helpful to verify weather the star has companion or not depend up on the existence of the time-delay. Then, we applied the technique on known binary stars and their orbital elements are previously published. Finally, we identified some new short orbital period δSct pulsating stars and obtained their orbital frequency and period with the same procedures. Because of with our attempts we succeeded and verified the applicability of the method (the Binarogram method) on these stars (i.e short orbital period) for the first time, we expect that our present study will play a great role for similar study and to improve our binary statistics.

scholarly journals Non-Adiabatic Seismic Study of The Thin Convective Envelope of δ Scuti Stars

2004 ◽  
Vol 193 ◽  
pp. 470-473
Author(s):  
M.-A. Dupret ◽  
A. Grigahcène ◽  
R. Garrido ◽  
J. Montalban ◽  
M. Gabriel ◽  
...  
Keyword(s):  
Instability Strip ◽  
Full Spectrum ◽  
Convective Envelope ◽  
Theoretical Predictions ◽  
Mode Stability ◽  
Different Color ◽  
Mixing Length Theory ◽  
Scuti Stars ◽  
Δ Scuti Stars ◽  
Phase Differences

AbstractFor δ Sct stars, the theoretical predictions of a non-adiabatic pulsation code are very dependent on the characteristics of the thin convective envelope of the models (Balona & Evers 1999). The treatment of the non-adiabatic interaction between convection and pulsation also has a significant impact on the results, particularly near the red edge of the instability strip. The non-adiabatic theoretical predictions can be tested upon observations by comparing them to the amplitude ratios and phase differences as observed in different color passbands (Dupret et al. 2003). In the first part of this paper, we compare the results obtained by adopting different treatments of convection in the interior and atmosphere models: mixing-length theory (MLT) and full spectrum of turbulence (FST) (Canuto et al. 1996, CGM). In the second part, we examine the problem of the interaction between convection and pulsation and compare the mode stability obtained with and without including time-dependent convection in our non-adiabatic code.

scholarly journals Delta Scuti stars in the Praesepe cluster observed by the MOST satellite

2012 ◽  
Vol 333 (2) ◽  
pp. 131-137 ◽  
Author(s):  
M. Breger ◽  
M. Hareter ◽  
M. Endl ◽  
R. Kuschnig ◽  
W.W. Weiss ◽  
...  
Keyword(s):  
Delta Scuti ◽  
Scuti Stars
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