scholarly journals Effects of "extra-mixing" processes on the periods of high-order gravity modes in main-sequence stars

2007 ◽  
Vol 147 ◽  
pp. 89-92 ◽  
Author(s):  
A. Miglio
Keyword(s):  
Main Sequence ◽  
High Order ◽  
Main Sequence Stars ◽  
Mixing Processes

scholarly journals Light elements in massive single and binary stars

2009 ◽  
Vol 5 (S268) ◽  
pp. 411-420 ◽  
Author(s):  
N. Langer ◽  
I. Brott ◽  
M. Cantiello ◽  
S. E. de Mink ◽  
R. G. Izzard ◽  
...  
Keyword(s):  
Binary Stars ◽  
Main Sequence ◽  
Diagnostic Value ◽  
Light Elements ◽  
Main Sequence Stars ◽  
Mixing Processes ◽  
Transfer Event ◽  
Internal Mixing ◽  
Early Type Stars

AbstractWe highlight the role of the light elements (Li, Be, B) in the evolution of massive single and binary stars, which is largely restricted to a diagnostic value, and foremost so for the element boron. However, we show that the boron surface abundance in massive early type stars contains key information about their foregoing evolution which is not obtainable otherwise. In particular, it allows to constrain internal mixing processes and potential previous mass transfer event for binary stars (even if the companion has disappeared). It may also help solving the mystery of the slowly rotating nitrogen-rich massive main sequence stars.

scholarly journals Beryllium abundances along the evolutionary sequence of the open cluster IC 4651

2009 ◽  
Vol 5 (S268) ◽  
pp. 357-358 ◽  
Author(s):  
Rodolfo Smiljanic ◽  
L. Pasquini ◽  
C. Charbonnel ◽  
N. Lagarde
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
High Signal ◽  
Evolutionary Sequence ◽  
Main Sequence Stars ◽  
Signal To Noise ◽  
Mixing Processes ◽  
Hydrodynamical Models ◽  
Spectrum Synthesis ◽  
Hertzsprung Gap

AbstractThe simultaneous investigation of Li and Be in stars is a powerful tool in the study of the evolutionary mixing processes. Here, we present beryllium abundances in stars along the whole evolutionary sequence of the open cluster IC 4651. This cluster has a metallicity of [Fe/H] = +0.11 and an age of 1.2 or 1.7 Gyr. Abundances have been determined from high-resolution, high signal-to-noise UVES spectra using spectrum synthesis and model atmospheres. Lithium abundances for the same stars were determined in a previous work. Confirming previous results, we find that the Li dip is also a Be dip. For post-main-sequence stars, the Be dilution starts earlier within the Hertzsprung gap than expected from classical predictions, as does the Li dilution. Theoretical hydrodynamical models are able to reproduce well all the observed features.

scholarly journals Evolutionary effects of stellar rotation of massive stars in their pre-supernova environments

2010 ◽  
Vol 6 (S272) ◽  
pp. 99-100
Author(s):  
Brenda Pérez-Rendón ◽  
Horacio Pineda-León ◽  
Alfredo Santillán ◽  
Liliana Hernández-Cervantes
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Main Sequence ◽  
Massive Stars ◽  
Stellar Winds ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Mixing Processes ◽  
Circumstellar Medium ◽  
Loss Rates

AbstractMassive main sequence stars are fast rotators. Stellar rotation affects massive stellar rotation due to rotationally induced mixing processes, the increase of mass loss rates, etc. and also affects the circumstellar medium due to their interaction with the stellar wind. The parameters of stellar winds depends on stellar parameters so the wind parameters change as the star evolves, coupling the evolution of circumstellar medium to the star itself. In this work we used a stellar code to build models of two massive stars (30 and 40 M⊙) and we used their wind parameters to simulate the hydrodynamics of their surrounding gas with the ZEUS-3D code in order to explore the effects of stellar rotation in the pre-supernova environments.

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

On The Radii of Ap Stars

1976 ◽  
Vol 32 ◽  
pp. 49-55 ◽  
Author(s):  
F.A. Catalano ◽  
G. Strazzulla
Keyword(s):  
Observational Data ◽  
Line Width ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Ap Stars

SummaryFrom the analysis of the observational data of about 100 Ap stars, the radii have been computed under the assumption that Ap are main sequence stars. Radii range from 1.4 to 4.9 solar units. These values are all compatible with the Deutsch's period versus line-width relation.

Pre–Main-Sequence Stars in the Young Galactic Cluster IC 4996: A CCD Photometric Study

1998 ◽  
Vol 116 (4) ◽  
pp. 1801-1809 ◽  
Author(s):  
Antonio J. Delgado ◽  
Emilio J. Alfaro ◽  
André Moitinho ◽  
José Franco
Keyword(s):  
Main Sequence ◽  
Photometric Study ◽  
Main Sequence Stars ◽  
Galactic Cluster

Photoionized and Photodissociated Regions around Main‐Sequence Stars

1998 ◽  
Vol 501 (1) ◽  
pp. 192-206 ◽  
Author(s):  
Rosa Izela Diaz‐Miller ◽  
Jose Franco ◽  
Steven N. Shore
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars

scholarly journals Helium, [Fe/H] Abundances and the HR (Log TEFF, MBol) Diagram With Hipparcos Data of The Four Nearest Open Clusters: Hyades, Coma Berenices, The Pleiades and Praesepe

1998 ◽  
Vol 11 (1) ◽  
pp. 565-565
Author(s):  
G. Cayrel de Strobel ◽  
R. Cayrel ◽  
Y. Lebreton
Keyword(s):  
Main Sequence ◽  
Open Clusters ◽  
Main Sequence Stars ◽  
Spectroscopic Analyses ◽  
Solar Metallicity ◽  
Metal Abundances ◽  
The Mean ◽  
The Moment ◽  
The One ◽  
Best Fit

After having studied in great detail the observational HR diagram (log Teff, Mbol) composed by 40 main sequence stars of the Hyades (Perryman et al.,1997, A&A., in press), we have tried to apply the same method to the observational main sequences of the three next nearest open clusters: Coma Berenices, the Pleiades, and Praesepe. This method consists in comparing the observational main sequence of the clusters with a grid of theoretical ZAMSs. The stars composing the observational main sequences had to have reliable absolute bolometric magnitudes, coming all from individual Hipparcos parallaxes, precise bolometric corrections, effective temperatures and metal abundances from high resolution detailed spectroscopic analyses. If we assume, following the work by Fernandez et al. (1996, A&A,311,127), that the mixing-lenth parameter is solar, the position of a theoretical ZAMS, in the (log Teff, Mbol) plane, computed with given input physics, only depends on two free parameters: the He content Y by mass, and the metallicity Z by mass. If effective temperature and metallicity of the constituting stars of the 4 clusters are previously known by means of detailed analyses, one can deduce their helium abundances by means of an appropriate grid of theoretical ZAMS’s. The comparison between the empirical (log Teff, Mbol) main sequence of the Hyades and the computed ZAMS corresponding to the observed metallicity Z of the Hyades (Z= 0.0240 ± 0.0085) gives a He abundance for the Hyades, Y= 0.26 ± 0.02. Our interpretation, concerning the observational position of the main sequence of the three nearest clusters after the Hyades, is still under way and appears to be greatly more difficult than for the Hyades. For the moment we can say that: ‒ The 15 dwarfs analysed in detailed in Coma have a solar metallicity: [Fe/H] = -0.05 ± 0.06. However, their observational main sequence fit better with the Hyades ZAMS. ‒ The mean metallicity of 13 Pleiades dwarfs analysed in detail is solar. A metal deficient and He normal ZAMS would fit better. But, a warning for absorption in the Pleiades has to be recalled. ‒ The upper main sequence of Praesepe, (the more distant cluster: 180 pc) composed by 11 stars, analysed in detail, is the one which has the best fit with the Hyades ZAMS. The deduced ‘turnoff age’ of the cluster is slightly higher than that of the Hyades: 0.8 Gyr instead of 0.63 Gyr.

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