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 Masses of c-type RR Lyrae Variables in Globular Clusters

1993 ◽  
Vol 139 ◽  
pp. 324-324
Author(s):  
C. Cacciari ◽  
A. Bruzzi
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Stellar Mass ◽  
Type I ◽  
Pulsation Period ◽  
Rr Lyrae ◽  
Stellar Pulsation ◽  
Controversial Problem ◽  
The One ◽  
Image Position

The mass of RR Lyrae variables has been a controversial problem for about a decade: while the stellar evolution theory predicts masses ranging between 0.65 and 0.75 M⊙ for Oosterhoff type I and II clusters respectively, the stellar pulsation theory predicts smaller masses (0.55 and 0.65 respectively) using the double-mode pulsators. Simon (1990, M.N.R.A.S. 246, 70), comparing hydrodynamical models with observed stars by means of Fourier parameters, has found relations between the stellar mass and its luminosity, pulsation period, Helium content and Fourier parameter ϕ31. Combining his equations we obtain:(1)from which one can estimate the stellar mass by using the observable quantities P and ϕ31 and a luminosity scale, e.g. the one derived by Cacciari, Clementini and Fernley (1992, Astrophys. J. in press).

scholarly journals Central Stars of Young Planetary Nebulae - A New Class of Variables

2003 ◽  
Vol 209 ◽  
pp. 237-238 ◽  
Author(s):  
G. Handler
Keyword(s):  
Mass Loss ◽  
Radial Velocity ◽  
Time Scales ◽  
Variable Star ◽  
Planetary Nebulae ◽  
Stellar Mass ◽  
New Class ◽  
Stellar Pulsation ◽  
Stellar Pulsations ◽  
Central Stars

A new class of variable star is proposed. These are variable central stars of young Planetary Nebulae exhibiting roughly sinusoidal (semi)regular photometric and/or radial velocity variations with time scales of several hours. Fourteen of these objects have been identified. Their temperatures are between 25000 and 50000 K and most show hydrogen-rich spectra. The most likely reason for the variability is stellar pulsation. Another possibility would be variable stellar mass loss, but in that case the mechansism causing it must be different from that operating in massive O stars. We speculate that it actually is the stellar pulsations which cause mass loss mdulations.

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 Stellar masers, circumstellar envelopes and supernova remnants

2007 ◽  
Vol 3 (S242) ◽  
pp. 236-245
Author(s):  
Athol J. Kemball
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Supernova Remnants ◽  
Stellar Mass ◽  
Stellar Atmospheres ◽  
Late Type ◽  
Open Future ◽  
Circumstellar Envelopes ◽  
Recent Advances

AbstractThis paper reviews recent advances in the study or circumstellar masers and masers found toward supernova remnants. The review is organized by science focus area, including the astrophysics of extended stellar atmospheres, stellar mass-loss processes and outflows, late-type evolved stellar evolution, stellar maser excitation and chemistry, and the use of stellar masers as independent distance estimators. Masers toward supernova remnants are covered separately. Recent advances and open future questions in this field are explored.

scholarly journals Pulsation and mass loss across the H-R diagram: From OB stars to Cepheids to red supergiants

2013 ◽  
Vol 9 (S301) ◽  
pp. 205-212
Author(s):  
Hilding R. Neilson
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Massive Stars ◽  
Main Sequence Stars ◽  
Ob Stars ◽  
Classical Cepheids ◽  
Growing Body ◽  
Red Supergiants ◽  
Enhance Mass

AbstractBoth pulsation and mass loss are commonly observed in stars and are important ingredients for understanding stellar evolution and structure, especially for massive stars. There is a growing body of evidence that pulsation can also drive and enhance mass loss in massive stars and that pulsation-driven mass loss is important for stellar evolution. In this review, I will discuss recent advances in understanding pulsation-driven mass loss in massive main-sequence stars, classical Cepheids and red supergiants and present some challenges remaining.

scholarly journals Evidence for Stellar Evolution in Mira Variables

1998 ◽  
Vol 11 (1) ◽  
pp. 356-356
Author(s):  
Patricia A Whitelock
Keyword(s):  
Mass Loss ◽  
Real Time ◽  
Time Evolution ◽  
Stellar Evolution ◽  
Evolutionary Status ◽  
Late Type ◽  
Chemical Changes ◽  
Mira Variables ◽  
Late Stages ◽  
Insight Into

After briefly reviewing our understanding of Miras and their evolutionary status, three aspects of real-time evolution in these and related stars are examined: 1.Chemical changes (O-rich to C-rich) due to third dredge-up,2.Period changes due to the effects of the helium shell-flash,3.The existence of ‘fossil’ dust and gas shells. Studies of resolved gas and dust shells are highlighted as particularly interesting. They will enable us to examine the mass-loss histories of many late-type stars over the last ten thousand years or so. Such observations have only recently become technically feasible and they are expected to provide important new insight into the late stages of stellar evolution.

scholarly journals Supernova lightCURVE POPulation Synthesis II: Validation against supernovae with an observed progenitor

2019 ◽  
Vol 36 ◽  
Author(s):  
J. J. Eldridge ◽  
N. -Y. Guo ◽  
N. Rodrigues ◽  
E. R. Stanway ◽  
L. Xiao
Keyword(s):  
Light Curve ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Stellar Mass ◽  
Light Curves ◽  
Explosion Energy ◽  
Initial Mass ◽  
Multiple Models ◽  
Population Synthesis ◽  
Single Star

Abstract We use the results of a supernova light-curve population synthesis to predict the range of possible supernova light curves arising from a population of single-star progenitors that lead to type IIP supernovae. We calculate multiple models varying the initial mass, explosion energy, nickel mass and nickel mixing and then compare these to type IIP supernovae with detailed light curve data and pre-explosion imaging progenitor constraints. Where a good fit is obtained to observations, we are able to achieve initial progenitor and nickel mass estimates from the supernova lightcurve that are comparable in precision to those obtained from progenitor imaging. For 2 of the 11 IIP supernovae considered our fits are poor, indicating that more progenitor models should be included in our synthesis or that our assumptions, regarding factors such as stellar mass loss rates or the rapid final stages of stellar evolution, may need to be revisited in certain cases. Using the results of our analysis we are able to show that most of the type IIP supernovae have an explosion energy of the order of log(Eexp/ergs) = 50.52 ± 0.10 and that both the amount of nickel in the supernovae and the amount of mixing may have a dependence on initial progenitor mass.

Mass Loss from Stars

1970 ◽  
Vol 39 ◽  
pp. 272-280
Author(s):  
S. R. Pottasch
Keyword(s):  
Interstellar Medium ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Stellar Mass ◽  
High Luminosity ◽  
Similar Extent ◽  
Probable Loss ◽  
Loss Rates

In this summary we shall attempt to evaluate the mass loss from several kinds of high luminosity stars, especially planetary nebulae, OB supergiants and M giants and supergiants. The purpose is to give an observational basis for the discussion of the mechanism of mass loss and of the consequences of stellar mass loss for the interstellar medium and for stellar evolution. For reasons which will presently be discussed, we are now certain that mass loss is occurring in all the objects mentioned, and probably to a similar extent in all high luminosity stars as well. The precise values of the mass loss rate are uncertain at present; for some objects the uncertainty will be large (two orders of magnitude) and have important influence on the consequences of the mass loss. Therefore we shall discuss in some detail how the different loss rates quoted in the literature have been obtained and what assumptions have been made (see also the Report by Boyarchuk, p. 281). On the basis of this discussion we will indicate the most probable loss rates and their consequences, always remembering the possible influence of the uncertainties.

scholarly journals Updated theoretical period–age and period–age–colour relations for Galactic Classical Cepheids: an application to the Gaia DR2 sample

2020 ◽  
Vol 496 (4) ◽  
pp. 5039-5051
Author(s):  
Giulia De Somma ◽  
Marcella Marconi ◽  
Santi Cassisi ◽  
Vincenzo Ripepi ◽  
Silvio Leccia ◽  
...  
Keyword(s):  
Mass Loss ◽  
Age Distribution ◽  
Theoretical Framework ◽  
Distribution Analysis ◽  
Chemical Abundance ◽  
Instability Strip ◽  
Abundance Pattern ◽  
The Core ◽  
Classical Cepheids ◽  
The Impact

ABSTRACT Updated evolutionary and pulsational model predictions are combined in order to interpret the properties of Galactic Classical Cepheids in the Gaia Data Release 2. In particular, the location of the instability strip boundaries and the analytical relations connecting pulsation periods to the intrinsic stellar parameters are combined with evolutionary tracks to derive reliable and accurate period–age and the first theoretical period–age–colour relations in the Gaia bands for a solar chemical abundance pattern (Z = 0.02, Y = 0.28). The adopted theoretical framework takes into account possible variations in the mass–luminosity relation for the core helium-burning stage as due to changes in the core convective overshooting and/or mass-loss efficiency, as well as the impact on the instability strip boundaries due to different assumptions for superadiabatic convection efficiency. The inferred period–age and period–age–colour relations are applied to a selected sample of both fundamental and first overtone Gaia Cepheids, and individual ages for the various adopted theoretical scenarios are derived. The retrieved age distributions confirm that a variation in the efficiency of superadiabatic convection in the pulsational model computations has a negligible effect, whereas a brighter mass–luminosity relation, as produced by mild overshooting, rotation, or mass-loss, implies significantly older age predictions. Moreover, older Cepheids are found at larger Galactocentric distances, while first overtone Cepheids are found to be systematically older than the fundamental ones. The comparison with independent age distribution analysis in literature supports the predictive capability of current theoretical framework.

scholarly journals Star clusters as laboratories for stellar and dynamical evolution

2010 ◽  
Vol 368 (1913) ◽  
pp. 755-782 ◽  
Author(s):  
Jason S. Kalirai ◽  
Harvey B. Richer
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
First Generation ◽  
Main Sequence ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Theoretical Studies ◽  
Chemical Enrichment

Open and globular star clusters have served as benchmarks for the study of stellar evolution owing to their supposed nature as simple stellar populations of the same age and metallicity. After a brief review of some of the pioneering work that established the importance of imaging stars in these systems, we focus on several recent studies that have challenged our fundamental picture of star clusters. These new studies indicate that star clusters can very well harbour multiple stellar populations, possibly formed through self-enrichment processes from the first-generation stars that evolved through post-main-sequence evolutionary phases. Correctly interpreting stellar evolution in such systems is tied to our understanding of both chemical-enrichment mechanisms, including stellar mass loss along the giant branches, and the dynamical state of the cluster. We illustrate recent imaging, spectroscopic and theoretical studies that have begun to shed new light on the evolutionary processes that occur within star clusters.

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