Stellar Rotation and Stellar Evolution among Cepheids and Other Luminous Stars in the Hertzsprung Gap

1966 ◽  
Vol 144 ◽  
pp. 1008 ◽  
Author(s):  
Robert P. Kraft
Keyword(s):  
Stellar Evolution ◽  
Stellar Rotation ◽  
Hertzsprung Gap

scholarly journals Testing models of rotating stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 73-78
Author(s):  
Adrian T. Potter ◽  
Christopher A. Tout
Keyword(s):  
Angular Momentum ◽  
Stellar Evolution ◽  
Momentum Transport ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Rapid Rotation ◽  
Angular Momentum Transport ◽  
Free Parameters ◽  
Stellar Models ◽  
The Many

AbstractThe effects of rapid rotation on stellar evolution can be profound but we are only now starting to gather the data necessary to adequately determine the validity of the many proposed models of rotating stars. Some aspects of stellar rotation, particularly the treatment of angular momentum transport within convective zones, still remain very poorly explored. Distinguishing between different models is made difficult by the typically large number of free parameters in models compared with the amount of available data. This also makes it difficult to determine whether increasing the complexity of a model actually results in a better reflection of reality. We present a new code to straightforwardly compare different rotating stellar models using otherwise identical input physics. We use it to compare several models with different treatments for the transport of angular momentum within convective zones.

scholarly journals On Magnetic Mixing and Rotation in Stellar Evolution

1978 ◽  
Vol 80 ◽  
pp. 323-331
Author(s):  
Peter G. Gross
Keyword(s):  
Magnetic Fields ◽  
Stellar Evolution ◽  
Evolutionary Status ◽  
Relevant Parameter ◽  
Stellar Rotation ◽  
Convective Turbulence ◽  
Stellar Interior ◽  
Magnetic Mixing ◽  
Ap Stars

In this paper some thoughts and problems are presented from the viewpoint that the evolution of stars may play a key role in generating magnetic fields which, in turn, may affect the mixing of nuclearly processed elements from the stellar interior to the surface. The relevant parameter is stellar rotation which, upon interaction with convective turbulence driven by thermal instabilities, leads to the generation of magnetic fields. A possible connection to Bidelman's hypothesis on the evolutionary status of Ap stars is also discussed in the context of a post-core-helium-flash hypothesis.

scholarly journals Extended main sequence turnoffs in open clusters as seen by Gaia – II. The enigma of NGC 2509

2019 ◽  
Vol 491 (2) ◽  
pp. 2129-2136 ◽  
Author(s):  
M de Juan Ovelar ◽  
S Gossage ◽  
S Kamann ◽  
N Bastian ◽  
C Usher ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Narrow Range ◽  
Open Cluster ◽  
Open Clusters ◽  
Stellar Rotation ◽  
Rotation Rates ◽  
Magnitude Diagram ◽  
Stellar Density

ABSTRACT We investigate the morphology of the colour–magnitude diagram (CMD) of the open cluster NGC 2509 in comparison with other Galactic open clusters of similar age using Gaia photometry. At ${\sim}900\,\rm {Myr}$ Galactic open clusters in our sample all show an extended main sequence turnoff (eMSTO) with the exception of NGC 2509, which presents an exceptionally narrow CMD. Our analysis of the Gaia data rules out differential extinction, stellar density, and binaries as a cause for the singular MSTO morphology in this cluster. We interpret this feature as a consequence of the stellar rotation distribution within the cluster and present the analysis with mesa Isochrones and Stellar Tracks (MIST) stellar evolution models that include the effect of stellar rotation on which we based our conclusion. In particular, these models point to an unusually narrow range of stellar rotation rates (Ω/Ωcrit, ZAMS = [0.4, 0.6]) within the cluster as the cause of this singular feature in the CMD of NGC 2509. Interestingly, models that do not include rotation are not as good at reproducing the morphology of the observed CMD in this cluster.

scholarly journals Butterfly diagram of a Sun-like star observed using asteroseismology

2018 ◽  
Vol 619 ◽  
pp. L9 ◽  
Author(s):  
M. Bazot ◽  
M. B. Nielsen ◽  
D. Mary ◽  
J. Christensen-Dalsgaard ◽  
O. Benomar ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Stellar Evolution ◽  
Theoretical Models ◽  
Observational Constraint ◽  
Stellar Rotation ◽  
Magnetic Field Generation ◽  
Rotation Rates ◽  
Butterfly Diagram ◽  
Stellar Magnetic Fields ◽  
First Time

Stellar magnetic fields are poorly understood, but are known to be important for stellar evolution and exoplanet habitability. They drive stellar activity, which is the main observational constraint on theoretical models for magnetic field generation and evolution. Starspots are the main manifestation of the magnetic fields at the stellar surface. In this study we measured the variation in their latitude with time, called a butterfly diagram in the solar case, for the solar analogue HD 173701 (KIC 8006161). To this end, we used Kepler data to combine starspot rotation rates at different epochs and the asteroseismically determined latitudinal variation in the stellar rotation rates. We observe a clear variation in the latitude of the starspots. It is the first time such a diagram has been constructed using asteroseismic data.

The Initial–Final Mass Relation for Close Low–Intermediate-Mass Binaries (Non-conservative Case)

2002 ◽  
Vol 187 ◽  
pp. 291-296
Author(s):  
Xuefei Chen ◽  
Zhanwen Han
Keyword(s):  
Stellar Evolution ◽  
Initial Mass ◽  
Mass Relation ◽  
Centre Of Mass ◽  
Mass Ratio ◽  
Intermediate Mass ◽  
Primary Mass ◽  
Binary Evolution ◽  
Hertzsprung Gap ◽  
Remnant Mass

AbstractEmploying Eggleton’s stellar evolution code, we carry out 150 runs of non-conservative Population I binary evolution calculations with the initial primary mass between 1 and 8 M⊙, the initial mass ratio q = M1/M2 between 1.1 and 4 and the onset of Roche lobe overflow (RLOF) at the early, middle or late Hertzsprung gap. We assume that 50 per cent of the mass lost from the primary during the RLOF is accreted on to the secondary, the other 50 per cent is lost from the system, carrying away the same specific angular momentum as the centre of mass of the primary. We find that the remnant mass depends on when the RLOF begins in the Hertzsprung-gap and the dependency increases with the primary mass. The remnant mass, however, does not depend much on the initial mass ratio, as compared to conservative cases. For qi = 1.1, we fit a formula for the remnant mass as a function of the initial mass M1i of the primary and the radius of the primary at the onset of RLOF with an error less than 2.61 per cent.

scholarly journals Fitting formulae for evolution tracks of massive stars under extreme metal-poor environments for population synthesis calculations and star cluster simulations

2020 ◽  
Vol 495 (4) ◽  
pp. 4170-4191 ◽  
Author(s):  
Ataru Tanikawa ◽  
Takashi Yoshida ◽  
Tomoya Kinugawa ◽  
Koh Takahashi ◽  
Hideyuki Umeda
Keyword(s):  
Stellar Evolution ◽  
Massive Stars ◽  
Star Cluster ◽  
Population Synthesis ◽  
Solar Mass ◽  
Helium Burning ◽  
Binary Black Holes ◽  
Extreme Metal ◽  
Hertzsprung Gap ◽  
Good Agreement

ABSTRACT We have devised fitting formulae for evolution tracks of massive stars with 8 ≲ M/M⊙ ≲ 160 under extreme metal-poor (EMP) environments for log (Z/Z⊙) = −2, −4, −5, −6, and −8, where M⊙ and Z⊙ are the solar mass and metallicity, respectively. Our fitting formulae are based on reference stellar models which we have newly obtained by simulating the time evolutions of EMP stars. Our fitting formulae take into account stars ending with blue supergiant (BSG) stars, and stars skipping Hertzsprung gap phases and blue loops, which are characteristics of massive EMP stars. In our fitting formulae, stars may remain BSG stars when they finish their core Helium burning phases. Our fitting formulae are in good agreement with our stellar evolution models. We can use these fitting formulae on the sse, bse, nbody4, and nbody6 codes, which are widely used for population synthesis calculations and star cluster simulations. These fitting formulae should be useful to make theoretical templates of binary black holes formed under EMP environments.

scholarly journals The role of rotation in stellar evolution

1984 ◽  
Vol 105 ◽  
pp. 475-489
Author(s):  
Jean-Louis Tassoul
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Direct Consequence ◽  
Axial Rotation ◽  
Stellar Structure ◽  
Spherically Symmetric ◽  
Stellar Rotation ◽  
Solar Differential Rotation ◽  
Effects Of Rotation

During the seventeenth century, in the wake of the discovery of the solar differential rotation, some scientists argued that stellar variability was a direct consequence of axial rotation, the spinning body showing alternately its bright (unspotted) and dark (spotted) hemispheres to the observer (Brunet 1931). Although this idea did not withstand the passage of time, it is nevertheless an interesting one because it is clearly indicative of the kind of fascination stellar rotation has aroused since its inception. And yet, at this writing there is no longer any doubt that spherically symmetric models do explain the major observed properties of stars. Moreover, if one excepts the very early and very late moments of a star's lifetime, the effects of rotation on stellar structure are apparently dynamically unimportant (e.g., Tassoul 1978, hereafter T.R.S.; Moss and Smith 1981, and references therein). What is the purpose, then, to discuss the role of rotation on the main-sequence and post-main-sequence phases of stellar evolution?

Stellar Evolution

1962 ◽  
Vol 11 (02) ◽  
pp. 137-143
Author(s):  
M. Schwarzschild
Keyword(s):  
Solar System ◽  
Stellar Evolution ◽  
Space Craft ◽  
New Techniques ◽  
Substantial Body ◽  
Individual Stars ◽  
The Past ◽  
Evolution Of Galaxies ◽  
History Of ◽  
Fast Flow

It is perhaps one of the most important characteristics of the past decade in astronomy that the evolution of some major classes of astronomical objects has become accessible to detailed research. The theory of the evolution of individual stars has developed into a substantial body of quantitative investigations. The evolution of galaxies, particularly of our own, has clearly become a subject for serious research. Even the history of the solar system, this close-by intriguing puzzle, may soon make the transition from being a subject of speculation to being a subject of detailed study in view of the fast flow of new data obtained with new techniques, including space-craft.

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