Download or read book Nonradial Pulsations of Rapidly Rotating delta Scuti Stars written by Edward James Kennelly and published by . This book was released on 1990 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nonradial Pulsations of Delta Scuti Stars written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An improved stellar model with a detailed composition structure is used to look at the nonradial behavior of a star near the region in the H-R diagram where the delta Scuti variables are found. Satisfactory solutions are obtained to the linear nonadiabatic equations. The newly calculated evolution models will be used in the future to study the pulsational stability of this class of stars. 4 refs., 2 figs., 1 tab.
Download or read book Amplitude Modulation of Pulsation Modes in Delta Scuti Stars written by Dominic M. Bowman and published by Springer. This book was released on 2017-09-07 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: This outstanding thesis by Dominic Bowman provides a thorough investigation of long-standing questions as to whether amplitude modulation is astrophysical, whether it offers insights into pulsating stars, and whether simple beating of modes with stable amplitudes is unrecognised because of a lack of frequency resolution. In this thesis, the author studied a uniform sample of 983 delta Scuti stars—the most common type of main-sequence heat engine pulsator—that were observed nearly continuously for 4 years at stunning photometric precision of only a few parts per million by the Kepler space mission. With no mission planned to supersede the Kepler 4-year data set, this thesis will stand as the definitive study of these questions for many years. With revolutionary photometric data from the planet-hunting Kepler space mission, asteroseismic studies have been carried out on many hundreds of main-sequence solar-type stars and about 10,000 red giants. It is easy to understand why those stochastically driven stars have highly variable amplitudes. Over much of the rest of the Hertzsprung–Russell (HR) diagram, stellar pulsations are driven by heat mechanisms, which are much more regular than the stochastic driving in solar-like pulsators. Yet for decades, amplitude and frequency modulation of pulsation modes have been observed in almost all types of heat-driven pulsating stars. The author shows that the amplitude and frequency modulation are astrophysical, and he has investigated their implications and prospects to provide new insights into the delta Scuti stars and the many other types of heat-engine pulsators across the HR diagram.
Download or read book Deriving the Structure of Pre supernovae and Delta Scuti Stars Using Nonradial Oscillations written by and published by . This book was released on 1998 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the final report of a three-year Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective is to learn more about the internal structure of two classes of variable stars, by using the observational data afforded by their pulsation properties. The authors updated the one-dimensional computer codes to calculate the evolution and pulsation frequencies of representative delta Scuti and LBV models. They compared the observed pulsation properties with model predictions in an iterative process to find a model (or models) with interior structures that matched the observational constraints for several delta Scuti stars. They carried out nonlinear hydrodynamic modeling of LBV envelopes and proposed a mechanism for their periodic outbursts. Finally, they began validation of a two-dimensional stellar evolution code that will be used to investigate the effects of rotation and hydrodynamic instabilities on the interior structure of these stars.
Download or read book Radial and Nonradial Periods of Delta Scuti written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Five periods have been discussed by Smith (1981) for the prototype variable star delta Scuti. The main one, at 0.193772 day, has long been identified as the radial fundamental mode. The others have not been clearly understood, but the second radial overtone is probably the correct identification for the 0.116366 day period. The other three at 0.186891, 0.189435, and 0.211157 day seem to be nonradial modes because of their long periods. The first of these seems to have l = 2 and m = -2 as observed by Smith. Table 1 gives these observed periods. Based on the Fitch (1981) nonradial pulsation constants, the 4.48 hour (.187 day) period seems to be a p1 mode, but as we shall see, we find that this identification is not very certain. The goal of this paper is to use our nonradial nonadiabatic computing program to predict periods in this range for a model matching the observed parameters of delta Scuti and to identify all five periods.
Download or read book Delta Scuti and Related Stars written by Michel Breger and published by . This book was released on 2000 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation Contains 35 papers presented as part of the August 1999 workshop. The opening papers review photometric techniques, spectroscopic techniques, and theoretical modeling of the pulsations. Shorter contributions discuss such topics as double-mode SX phoenicis variables in globular clusters, convective effects on p-mode stability in delta Scuti stars, problems encountered in the Hipparcos variable stars analysis, and a list of delta Scuti stars and their associated parameters. No subject index. Annotation c. Book News, Inc., Portland, OR (booknews.com)
Download or read book Understanding Variable Stars written by John R. Percy and published by Cambridge University Press. This book was released on 2007-05-24 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book was first published in 2007. Variable stars are those that change brightness. Their variability may be due to geometric processes such as rotation, or eclipse by a companion star, or physical processes such as vibration, flares, or cataclysmic explosions. In each case, variable stars provide unique information about the properties of stars, and the processes that go on within them. This book provides a concise overview of variable stars, including a historical perspective, an introduction to stars in general, the techniques for discovering and studying variable stars, and a description of the main types of variable stars. It ends with short reflections about the connection between the study of variable stars, and research, education, amateur astronomy, and public interest in astronomy. This book is intended for anyone with some background knowledge of astronomy, but is especially suitable for undergraduate students and experienced amateur astronomers who can contribute to our understanding of these important stars.
Download or read book Pulsating Stars written by Márcio Catelan and published by John Wiley & Sons. This book was released on 2015-02-02 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book surveys our understanding of stars which change in brightness because they pulsate. Pulsating variable stars are keys to distance scales inside and beyond the Milky Way galaxy. They test our understanding not only of stellar pulsation theory but also of stellar structure and evolution theory. Moreover, pulsating stars are important probes of the formation and evolution of our own and neighboring galaxies. Our understanding of pulsating stars has greatly increased in recent years as large-scale surveys of pulsating stars in the Milky Way and other Local Group galaxies have provided a wealth of new observations and as space-based instruments have studied particular pulsating stars in unprecedented detail.
Download or read book Linear Nonradial Pulsation Theory Lecture 7 written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Many of the upper main-sequence stars pulsate in spheroidal nonradial modes. We know this to be true in numerous cases, as we have tabulated for the .beta. Cephei and delta Scuti variables in previous lectures. However, we cannot identify the actual mode for any star except for the low-order pressure p and f modes of our sun. It remains a great challenge to clearly state what really is occurring, in the process we learn more about how stars evolve and pulsate.
Download or read book The Future of Asteroseismology written by Joyce Ann Guzik and published by Frontiers Media SA. This book was released on 2021-08-17 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Asteroseismology Across the HR Diagram written by Michael J. Thompson and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: We stand at the threshold of an exciting era of Asteroseismology. In a few months' time, the Canadian small-satellite asteroseismology mission MOST will be laun ched. Danish and French missions MONS and COROT should follow, with the ESA mission Eddington following in 2007/8. Helioseismology has proved spec tacularly successful in imaging the internal structure and dynamics of the Sun and probing the physics of the solar interior. Ground-based observations have detected solar-like oscillations on alpha Centauri A and other Sun-like stars, and diagnostics similar to those used in helioseismology are now being used to test and constrain the physics and evolutionary state of these stars. Multi-mode oscillations are being observed in an abundance of other stars, including slowly pulsating B stars (SPB stars), delta Scuti stars, Ap stars and the pulsating white dwarfs. New classes of pulsators continue to be discovered across the Hertzsprung-Russell diagram. For good reason it was decided to entitle our conference 'Asteroseismology Across the HR Diagram' . Yet the challenges still to be faced to make asteroseismology across the HR diagram a reality are formidable. Observation, data analysis and theory all pose hard problems to be overcome. In conceiving this meeting, the aim of the organisers was to facilitate a cross-fertilization of ideas and approaches between researchers working on different pulsators and with different areas of expertise. We venture to suggest that in this the conference was a great success.
Download or read book Literature 1992 Part 1 written by Astronomisches Recheninstitut and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 1456 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Astronomy and Astrophysics Abstracts" appearing twice a year has become oneof the fundamental publications in the fields of astronomy, astrophysics andneighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. The abstracts are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world.
Download or read book Challenges of asteroseismology in the era of space missions written by Javier Pascual Granado and published by Frontiers Media SA. This book was released on 2023-01-17 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Delta Scuti Variables Lecture 6 written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The class of variables near or on the upper main sequence, the delta Scuti variables, are not only the usual ones about the masses, radii, and luminosities, but also the age, rotation, element diffusion to change the surface layer composition, the occurance of convection and the presence of radial and nonradial pulsation modes. (GHT).
Download or read book Astronomy and Astrophysics Abstracts written by S. Böhme and published by Springer Science & Business Media. This book was released on 2013-12-14 with total page 1180 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the reviews: Astronomy and Astrophysics Abstracts has appeared in semi-annual volumes since 1969 and it has already become one of the fundamental publications in the fields of astronomy, astrophysics and neighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. ... The abstracts are classified under more than hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world." Space Science Reviews #1 "Dividing the whole field plus related subjects into 108 categories, each work is numbered and most are accompanied by brief abstracts. Fairly comprehensive cross-referencing links relevant papers to more than one category, and exhaustive author and subject indices are to be found at the back, making the catalogues easy to use. The series appears to be so complete in its coverage and always less than a year out of date that I shall certainly have to make a little more space on those shelves for future volumes." The Observatory Magazine #1
Download or read book Pulsations of B Star Models by an Opacity Mechanism written by and published by . This book was released on 1990 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The pulsation mechanism for B stars has been sought for 30 years. No proposed radial or nonradial mechanism, either deeply seated or in the surface layers, has been successful in explaining all the observational details. Perhaps the missing piece in the puzzle is the opacity of the stellar material. Many times the first author has tried to make unconventional surface compositions give instability, but none were ever found. We now propose that the sudden appearance of a tremendous number of iron lines, as the temperature rises above about 150,000 K, gives a high sensitivity of the opacity to temperature at the very low densities found in these blue giants. Opacities need to increase quickly to a factor of three or more above the Cox-Tabor (1976) values in the range around 200,000 K. These increases are the same needed to decrease theoretical period ratios of double-mode Cepheids and [delta] Scuti variables to agree better with observations for conventional yellow giant masses. The reason why not all B stars pulsate is that a slight primordial deficit in the iron abundance in the surface layer (1 × 10−6 of the mass) can reduce the opacity and its sensitivity to temperature. A slight amount of iron concentration by radiative levitation could make a star pulsate even if it did not originally have enough primordial iron to cause this opacity mechanism to operate. Then any slow slight mixing caused by the unstable nonradial pulsations could restabilize the pulsations as actually observed in [alpha] Vir and [beta] CMa. Rapid levitation and mixing for the very luminous B stars with their very low density envelopes could even explain the puzzling luminous blue variables with this standard [kappa] mechanism. Large amplitude pulsations like those seen in BW Vul would indicate a somewhat larger iron abundance compared to all other B stars.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1982 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
