scholarly journals Observations of evolutionary changes in the pulsation period of cepheids

1984 ◽  
Vol 105 ◽  
pp. 445-448
Author(s):  
L. Szabados
Keyword(s):  
Detailed Analysis ◽  
Stellar Evolution ◽  
Time Scale ◽  
Theoretical Work ◽  
Pulsation Period ◽  
First Approximation ◽  
Evolutionary Changes ◽  
Classical Cepheids ◽  
Cepheid Variables

In spite of the fact that Cepheid variables pulsate quite regularly their pulsation period remains constant only in the first approximation. The pulsation period is subject to variations because of stellar evolution. The calculations made by Hofmeister (1965) predicted that the evolutionary period changes of classical Cepheids should be observed on a time scale of several decades or longer. No detailed analysis of the observed period changes has been made since Hofmeister's fundamental theoretical work.

scholarly journals Pulsation Period Change & Classical Cepheids: Probing the Details of Stellar Evolution

2014 ◽  
Vol 9 (S307) ◽  
pp. 224-225
Author(s):  
Hilding R. Neilson ◽  
Alexandra C. Bisol ◽  
Ed Guinan ◽  
Scott Engle
Keyword(s):  
Mass Loss ◽  
Real Time ◽  
Stellar Evolution ◽  
Stellar Mass ◽  
Period Change ◽  
Pulsation Period ◽  
Instability Strip ◽  
Loss Mechanism ◽  
Stellar Pulsation ◽  
Classical Cepheids

AbstractMeasurements of secular period change probe real-time stellar evolution of classical Cepheids making these measurements powerful constraints for stellar evolution models, especially when coupled with interferometric measurements. In this work, we present stellar evolution models and measured rates of period change for two Galactic Cepheids: Polaris and l Carinae, both important Cepheids for anchoring the Cepheid Leavitt law (period-luminosity relation). The combination of previously-measured parallaxes, interferometric angular diameters and rates of period change allows for predictions of Cepheid mass loss and stellar mass. Using the stellar evolution models, We find that l Car has a mass of about 9 M⊙ consistent with stellar pulsation models, but is not undergoing enhanced stellar mass loss. Conversely, the rate of period change for Polaris requires including enhanced mass-loss rates. We discuss what these different results imply for Cepheid evolution and the mass-loss mechanism on the Cepheid instability strip.

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 Watching Stars Evolve: Rapid Evolutionary Changes of the Post-AGB Star - FG SGE

1998 ◽  
Vol 11 (1) ◽  
pp. 343-343
Author(s):  
E.F. Guinan ◽  
Yu. S. Efimov ◽  
S.J. Margheim
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Central Star ◽  
Dust Formation ◽  
Pulsation Period ◽  
Photometric System ◽  
Evolutionary Changes ◽  
History Of ◽  
Ubvri Photometry ◽  
Pn Stage

The variable post-AGB star FG Sge has provided an unique opportunity to study phenomenon which may be characteristic of the post-PN stage of stellar evolution. FG Sge is the central star in the 36-arcsec PN He 1-5 that over the last 50 yrs has been undergoing rapid evolutionary changes. Most notable are changes in temperature, luminosity, chemical composition and pulsation period. Starting in mid-1992, the star has undergone several large dimming events from which it has yet to recover. These events closely resemble the dimming events commonly observed in R CrB stars which result from dust formation in ejected envelopes. From all the evidence, it now appears that FG Sge has evolved into a R CrB star. In this paper we first summarize the recent photometric history of the FG Sge from UBVRI photometry obtained during 1990-1997. We then combine these data with earlier photometry to define the star’s light bevavior over the last 100 yrs. The photometry is also combined with available spectroscopic polarimetric, and IR observations. Particlar attention is given to comparing FG Sge’s post-dimming behavior with contemporaneous observations of R CrB itself, also done on the same photometric system.

scholarly journals Yellow Supergiants and R Coronae Borealis Stars

1995 ◽  
Vol 155 ◽  
pp. 143-154
Author(s):  
P.L. Cottrell
Keyword(s):  
Detailed Analysis ◽  
Observational Data ◽  
Stellar Evolution ◽  
Variable Stars ◽  
Important Conclusion ◽  
Photometric And Spectroscopic Observations ◽  
Cepheid Variables ◽  
R Coronae Borealis Stars ◽  
The Universe ◽  
Made In

AbstractThe study of luminous variable stars has important consequences both with respect to the scale of the Universe and for our understanding of the later stages of stellar evolution.This review will look at a number of groups of these stars, in particular the RV Tauri stars, the hydrogen-deficient Carbon (HdC) stars, including the R Coronae Borealis (RCB) stars and some aspects of Cepheid variables.Both photometric and spectroscopic observations will be presented to show the amount of progress that has been made in this area over the last several years. Links will be made to various models which are being used to understand the observational data.The most important conclusion is that there is still enormous scope for the acquisition and detailed analysis of data on the relatively bright members of these groups of stars. These can be used to provide further understanding of the more distant objects of each group and of the wider problems in astrophysics.

scholarly journals Evolutionary Changes in LUMINOUS STARS

1998 ◽  
Vol 11 (1) ◽  
pp. 346-346
Author(s):  
E. Zsldos
Keyword(s):  
Light Curve ◽  
19Th Century ◽  
Stellar Evolution ◽  
Colour Change ◽  
Light Curves ◽  
Appreciable Change ◽  
Luminous Blue Variables ◽  
Secular Changes ◽  
Evolutionary Changes ◽  
The 19Th Century

The light curves of luminous stars often show spectacular secular changes which can be connected to stellar evolution. Such events are, e.g. the outbursts of P Cygni in the 17th century and 77 Carinae in the last century. Both stars belong to the Luminous Blue Variables, but these changes are not restricted to blue stars. The light curve of HR 8752 (V509 Cassiopeiae) shows a certain similarity to that of the former two stars. When it was first catalogued in the middle of the 19th century, it had been a 6m star. During 100 years the star showed a secular brightening of lm. A similar yellow hypergiant, p Cassiopeiae produced at least two outbursts this century, though both have smaller amplitudes than it is in the case of the LBVs. Moreover, these yellow variables also have an apparently secular colour change: the B − V colour of HR 8752 is decreasing while that of ρ Cassiopeiae is increasing. In both cases evolutionary changes are possible but one cannot exclude other causes. Besides these well studied stars there are several other yellow hypergiants with promising light curves. One of the most interesting cases seems to be R Puppis, which was discovered to be variable in the last century, but then did not show any appreciable change in the following 70-80 years. In the late 1970s, however, it began to vary once more.

scholarly journals IRAS observations of classical cepheids

1987 ◽  
Vol 122 ◽  
pp. 227-228
Author(s):  
C. J. Butler ◽  
H. P. Deasy ◽  
P. A. Wayman
Keyword(s):  
Mass Loss ◽  
Classical Cepheids ◽  
Cepheid Variables ◽  
Loss Rates

IRAS observations of sources identified with cepheid variables are used to give estimates of observed mass-loss rates for those stars.

scholarly journals Eco-evolutionary dynamics

2009 ◽  
Vol 364 (1523) ◽  
pp. 1483-1489 ◽  
Author(s):  
F. Pelletier ◽  
D. Garant ◽  
A.P. Hendry
Keyword(s):  
Time Scale ◽  
Evolutionary Dynamics ◽  
Evolutionary Change ◽  
Ecological Change ◽  
Evolutionary Changes ◽  
Microevolutionary Change ◽  
Theoretical Developments ◽  
Rapid Evolutionary Change

Evolutionary ecologists and population biologists have recently considered that ecological and evolutionary changes are intimately linked and can occur on the same time-scale. Recent theoretical developments have shown how the feedback between ecological and evolutionary dynamics can be linked, and there are now empirical demonstrations showing that ecological change can lead to rapid evolutionary change. We also have evidence that microevolutionary change can leave an ecological signature. We are at a stage where the integration of ecology and evolution is a necessary step towards major advances in our understanding of the processes that shape and maintain biodiversity. This special feature about ‘eco-evolutionary dynamics’ brings together biologists from empirical and theoretical backgrounds to bridge the gap between ecology and evolution and provide a series of contributions aimed at quantifying the interactions between these fundamental processes.

scholarly journals Interpreting the Evolving Clumpy Shell Structure of IRC +10216 in Terms of Time Dependent Dust Shell Models

2003 ◽  
Vol 209 ◽  
pp. 127-128
Author(s):  
J. M. Winters ◽  
T. Blöcker ◽  
K.-H. Hofmann ◽  
G. Weigelt
Keyword(s):  
Time Scale ◽  
High Spatial Resolution ◽  
Light Curves ◽  
Infrared Light ◽  
Pulsation Period ◽  
Line Profiles ◽  
Dust Shell ◽  
Time Intervals ◽  
Stellar Pulsation ◽  
Shell Models

The prototypical dust-enshrouded carbon Mira IRC +10216 is known to exhibit intrinsic changes on a time scale of the order of only a few years as revealed, e.g., by CO infrared line profiles (Winters et al. 2000a), its infrared light curves, and by high spatial resolution monitoring in the infrared (Osterbart et al. 2000; Tuthill et al. 2000). In particular, the infrared light curves indicate a possible periodicity on a ≈ 20 yr time scale, i.e. that a recurrent phenomenon might lead to the observed variations. Such multi-periodicity time scales of several (≈ 10) stellar pulsation periods are predicted by consistent hydrodynamical models which include a proper treatment of dust formation (e.g. Winters et al. 2000b). In these models discrete dust layers form in time intervals which are several times longer than the typical pulsation period of an AGB star (Fleischer, Gauger, & Sedlmayr 1995; Höfner, Feuchtinger, & Dorfi 1995).

Coravel Radial-Velocity Curves for Cepheids in the Large Magellanic Cloud

1984 ◽  
Vol 88 ◽  
pp. 375-380
Author(s):  
M. Imbert ◽  
J. Andersen ◽  
A. Ardeberg ◽  
C. Bardin ◽  
W. Benz ◽  
...  
Keyword(s):  
Comparative Study ◽  
Radial Velocity ◽  
Stellar Evolution ◽  
Large Magellanic Cloud ◽  
Magellanic Clouds ◽  
Independent Determination ◽  
Fundamental Information ◽  
The Galaxy ◽  
Cepheid Variables

Radii and luminosities for Cepheid variables provide fundamental information on stellar evolution. Such data, obtained by the Baade-Wesselink method, are available and have been used for a number of galactic Cepheids. It is of particular interest to obtain corresponding data for Cepheids in the Magellanic Clouds. Firstly, this allows a comparative study of stellar evolution between the Galaxy and the Magellanic Clouds. Secondly, it provides data for an independent determination of the distance to the Magellanic Clouds.Radial-velocity observations have been made for a total of around 20 Cepheid variables in both the LMC and the SMC. All measurements were made with the photoelectric scanner CORAVEL attached to the Cassegrain focus of the Danish 1.54-m telescope at European Southern Observatory, La Silla, Chile. Observations were made from January 1981 through October 1983. The accuracy of individual radial-velocity observations is of the order of 1 km s−1. The B magnitudes of the six Cepheids presented range from 13.0 to 15.5.

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