scholarly journals Mode selection in pulsating stars

2013 ◽  
Vol 9 (S301) ◽  
pp. 265-272 ◽  
Author(s):  
Radosław Smolec
Keyword(s):  
Main Sequence ◽  
Mode Selection ◽  
Rr Lyrae Stars ◽  
Future Studies ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
Non Linear ◽  
Lyrae Stars

AbstractIn this review we focus on non-linear phenomena in pulsating stars: mode selection and amplitude limitation. Of many linearly excited modes, only a fraction is detected in pulsating stars. Which of them are excited, and why (the problem of mode selection), and to what amplitude (the problem of amplitude limitation) are intrinsically non-linear and still unsolved problems. Tools for studying these problems are briefly discussed and our understanding of mode selection and amplitude limitation in selected groups of self-excited pulsators is presented. We focus on classical pulsators (Cepheids and RR Lyrae stars) and main-sequence variables (δ Scuti and β Cephei stars). Directions of future studies are briefly discussed.

scholarly journals Theoretical UBVI Light Curves of Pulsating Stars

2000 ◽  
Vol 176 ◽  
pp. 334-337
Author(s):  
Michael U. Feuchtinger ◽  
Ernst A. Dorfi
Keyword(s):  
Radiative Transfer ◽  
Light Curves ◽  
Rr Lyrae Stars ◽  
Fourier Decomposition ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
Stellar Pulsation ◽  
Sample Application ◽  
Lyrae Stars ◽  
Good Agreement

AbstractBy performing detailed frequency-dependent radiative transfer computations we are able to calculate light curves in particular bandpasses from stellar pulsation models calculated by the Vienna nonlinear convective pulsation code. As a sample application we discuss UBVI light curves of RR Lyrae stars. The properties of these light curves are analyzed by means of standard Fourier decomposition, and a comparison to recent observations is performed. As main results we find a good agreement with important observed RR Lyrae properties like pulsation amplitudes and Fourier parameters in B, V, and I bands. Additionally, from the synthetic color curves we derive linear transformation laws between amplitudes as well as Fourier parameters in the different bandpasses.

Theoretical Problems of Beta Cephei Stars

1979 ◽  
Vol 46 ◽  
pp. 467-473
Author(s):  
Yoji Osaki
Keyword(s):  
Small Group ◽  
Spectral Type ◽  
Main Sequence ◽  
Massive Stars ◽  
Instability Strip ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
M 10 ◽  
Classical Cepheids ◽  
Lyrae Stars

The Beta Cephei (or Beta Canis Majoris) stars are a small group of pulsating variables of early spectral type. There are some 20 “classical” β Cephei stars, and several new or suspected variables in this group. The classical β Cephei stars are confined in a narrow “instability strip” which lies about 1 mag above and nearly parallel to the zero-age main-sequence of massive stars (M~10-20 M⊙). They are thus located far away from other well-known pulsating variables such as classical Cepheids and RR Lyrae stars in the HR diagram.

scholarly journals Observational Aspects of RR Lyrae Variables in Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 51-67 ◽  
Author(s):  
L. Rosino
Keyword(s):  
Globular Clusters ◽  
Absolute Magnitude ◽  
Good Test ◽  
Rr Lyrae Stars ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
Powerful Means ◽  
The Galaxy ◽  
Points Of View ◽  
Lyrae Stars

RR Lyrae variables play a prominent role in many of the problems of globular clusters, and from several points of view. In the first place they can be considered as pretty good indicators of population and distance; although they do not form a completely homogeneous set of stars, the knowledge of their mean absolute magnitude gives a powerful means of establishing distances within and outside the Galaxy, and hence of determining the form and size of the Galaxy itself. Moreover, the number of RR Lyrae stars in clusters, the relative frequency of RRc and RRab, types, the length of the transition periods, the array of colors, when correctly interpreted, give important information on the degree of evolution, age and chemical composition of the clusters. Placed as they are in a peculiar region of the H — R diagram of Population II, the RR Lyr variables can be used as a good test of the theories of advanced evolution or the models of pulsating stars.

scholarly journals The LMC Globular Cluster Hodge 11 (=SL 868)

1984 ◽  
Vol 108 ◽  
pp. 43-44
Author(s):  
L. L. Stryker ◽  
J. M. Nemec ◽  
J. E. Hesser ◽  
R.D. McClure
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Cluster ◽  
Open Clusters ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Lyrae Stars ◽  
Termination Point

The age of the star cluster H11 has been controversial for a number of years. The color-magnitude diagram (CMD) of Walker (1979) to V=21.5 was interpreted as an “…evolved main-sequence, whose termination point corresponds to an age of about 0.6 Gyr, but with a giant branch which is displaced blueward by about Δ (B-V)o=0.4 from the positions of the giant branches of open clusters of similar age in our Galaxy.” On the other hand, the integrated colors are similar to those of metal-poor globular clusters in the Galaxy (Freeman and Gascoigne 1977, and references therein), and “…incompatible with an age of say 0.3 Gyr.” Searle, Wilkinson and Bagnuolo (1980) classify it as Group VII, the oldest group. The system has no RR Lyrae stars (Graham and Nemec 1984).

scholarly journals Pulsation Variables in the AF stars of the Case Low-Dispersion Survey

1993 ◽  
Vol 139 ◽  
pp. 340-348
Author(s):  
T.D. Kinman
Keyword(s):  
Main Sequence ◽  
Galactic Plane ◽  
Balmer Line ◽  
Rr Lyrae Stars ◽  
Photoelectric Photometry ◽  
Blue Stragglers ◽  
Rr Lyrae ◽  
Wide Range ◽  
Lyrae Stars ◽  
Low Dispersion

AbstractThe AF stars are those of spectral types A and F that have been discovered on objective-prism plates taken with the Burrell Schmidt in the Case Low-Dispersion Northern Sky Survey (Pesch and Sanduleak, 1983). In SA 57, this survey is complete to V = 16.5. In this field and also in the Lick Astrograph RR Lyrae survey field RR 7 (in the anticenter) the AF stars comprise (a) blue horizontal branch stars and RR Lyrae stars of the halo and (b) stars which have the higher surface gravities of main sequence stars. The two groups can be separated primarily by their differing Balmer jumps and Balmer line-widths. The latter group (which may well include blue stragglers of both Pop I and Pop II) extends some 10 kpc above the galactic plane and shows a wide range of metallicity. Photoelectric photometry of this AF star sample has allowed the detection field RR Lyrae stars of lower-amplitudes than could have been found by conventional blinking techniques; this has led to a significant increase in the number of RR Lyrae stars that are known in SA 57 and RR 7. The cooler main sequence and/or blue straggler AF stars lie in the zone of pulsational instability and one higher-amplitude δ-Scuti star was detected in field RR 7. It is suggested that these AF stars provide a good sample for studying the incidence of pulsation in the population of older stars that extends beyond the thin disk.

scholarly journals Variable Stars and Evolution in Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 187-195
Author(s):  
Pierre Demarque
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Variable Stars ◽  
Rr Lyrae Stars ◽  
The Past ◽  
Rr Lyrae ◽  
Lyrae Stars ◽  
Distance Indicators

Traditionally, cluster variables have been used as distance indicators and have in this sense played an important role in our understanding of stellar evolution. In particular, the determination of the distance moduli of globular clusters and of the absolute magnitude of the main sequence turnoff, thus yielding the ages of the cluster, have relied heavily in the past on observations of RR Lyrae stars.

scholarly journals The Baade–Becker–Wesselink technique and the fundamental astrophysical parameters of Cepheids

2012 ◽  
Vol 8 (S289) ◽  
pp. 195-202
Author(s):  
Alexey S. Rastorguev ◽  
Andrey K. Dambis ◽  
Marina V. Zabolotskikh ◽  
Leonid N. Berdnikov ◽  
Natalia A. Gorynya
Keyword(s):  
A Priori ◽  
New Technique ◽  
Rr Lyrae Stars ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
Colour Excess ◽  
Classical Cepheids ◽  
Lyrae Stars ◽  
Intrinsic Colour ◽  
Modelling Approach

AbstractThe Baade–Becker–Wesselink (BBW) method remains one of most often used tools to derive a full set of Cepheid astrophysical parameters. The surface brightness version of the BBW technique was preferentially used during the past few decades to calculate Cepheid radii and to improve period–luminosity–colour relations. Its implementation requires a priori knowledge of Cepheid reddening values. We propose a new version of the BBW technique, which allows one to independently determine the colour excess and the intrinsic colour of a radially pulsating star, in addition to its radius, luminosity and distance. The new technique is a generalization of the Balona light curve-modelling approach. The method also allows calibration of the function F(CI0) = BC(CI0) + 10 log [Teff (CI0)] for the class of pulsating stars considered. We apply this technique to a number of classical Cepheids with very accurate light and radial-velocity curves. The new technique can also be applied to other pulsating variables, e.g., RR Lyrae stars. We also discuss the possible dependence of the projection factor on the pulsation phase.

scholarly journals Pulsating Stars and the Distance Scale - I

1995 ◽  
Vol 155 ◽  
pp. 198-206
Author(s):  
Alistair R. Walker
Keyword(s):  
Distance Scale ◽  
Rr Lyrae Stars ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Near Future ◽  
Lyrae Stars

AbstractA summary is given of recent measurements, by various methods, of the absolute magnitudes for RR Lyrae stars. Calibrations within our galaxy, using the Baade-Wesselink method and by Statistical Parallaxes, give a result that is some 0.2–0.3 mag fainter than is obtained by all other methods considered. The resolution of this conundrum will be likely in the near future when new and improved datasets become available.

scholarly journals On the Existence of Luminosity Differences between HB Field and Cluster Stars

2000 ◽  
Vol 176 ◽  
pp. 265-265
Author(s):  
E. Carretta ◽  
R. G. Gratton ◽  
G. Clementini
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Distance Scale ◽  
Horizontal Branch ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Intrinsic Difference ◽  
General Field ◽  
Lyrae Stars

AbstractThe discrepancy between the long distance scale as derived, e.g., from Hipparcos-based distances to globular clusters via main sequence fitting to local subdwarfs, and the short distance scale as derived, e.g., from the absolute magnitude of field RR Lyrae stars via statistical parallaxes and the Baade–Wesselink method, could be accounted for if an intrinsic difference in luminosity of about 0.1−0.2 mag were found to exist between horizontal branch (HB) stars populating the sparse general field and the dense globular clusters.

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