scholarly journals Statistical Fitting of Evolutionary Models to Rotation Rates of Sun-like Stars

2021 ◽  
Vol 913 (1) ◽  
pp. 75
Author(s):  
Angela A. Breimann ◽  
Sean P. Matt ◽  
Tim Naylor
Keyword(s):  
Evolutionary Models ◽  
Rotation Rates ◽  
Statistical Fitting

scholarly journals γ Doradus stars as a test of angular momentum transport models

2019 ◽  
Vol 626 ◽  
pp. A121 ◽  
Author(s):  
R.-M. Ouazzani ◽  
J. P. Marques ◽  
M.-J. Goupil ◽  
S. Christophe ◽  
V. Antoci ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Evolutionary Models ◽  
Intermediate Mass ◽  
Angular Momentum Transport ◽  
Rotation Rates ◽  
Giant Stars ◽  
Intermediate Mass Stars ◽  
Red Giant ◽  
Core Rotation

Helioseismology and asteroseismology of red giant stars have shown that distribution of angular momentum in stellar interiors, and the evolution of this distribution with time remains an open issue in stellar physics. Owing to the unprecedented quality and long baseline of Kepler photometry, we are able to seismically infer internal rotation rates in γ Doradus stars, which provide the main-sequence counterpart to the red-giants puzzle. Here, we confront these internal rotation rates to stellar evolution models which account for rotationally induced transport of angular momentum, in order to test angular momentum transport mechanisms. On the one hand, we used a stellar model-independent method developed by our team in order to obtain accurate, seismically inferred, buoyancy radii and near-core rotation for 37 γ Doradus stars observed by Kepler. We show that the stellar buoyancy radius can be used as a reliable evolution indicator for field stars on the main sequence. On the other hand, we computed rotating evolutionary models of intermediate-mass stars including internal transport of angular momentum in radiative zones, following the formalism developed in the series of papers started by Zahn (1992, A&A, 265, 115), with the CESTAM code. This code calculates the rotational history of stars from the birth line to the tip of the RGB. The initial angular momentum content has to be set initially, which is done here by fitting rotation periods in young stellar clusters. We show a clear disagreement between the near-core rotation rates measured in the sample and the rotation rates obtained from the evolutionary models including rotationally induced transport of angular momentum following Zahn’s prescriptions. These results show a disagreement similar to that of the Sun and red giant stars in the considered mass range. This suggests the existence of missing mechanisms responsible for the braking of the core before and along the main sequence. The efficiency of the missing mechanisms is investigated. The transport of angular momentum as formalized by Zahn and Maeder cannot explain the measurements of near-core rotation in main-sequence intermediate-mass stars we have at hand.

A critical test to disentangle the role of overshooting and rotation in stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 375-376
Author(s):  
G. Costa ◽  
L. Girardi ◽  
A. Bressan ◽  
P. Marigo ◽  
Y. Chen ◽  
...  
Keyword(s):  
Bayesian Estimation ◽  
Massive Stars ◽  
Estimation Method ◽  
Eclipsing Binaries ◽  
Evolutionary Models ◽  
Critical Test ◽  
Rotation Rates ◽  
Reasonable Explanation ◽  
Convective Core

AbstractWe study the mixing in low-intermediate massive stars using eclipsing binaries. We compute stellar evolutionary models with a varying convective core overshooting parameter and different rotation rates. Using a Bayesian estimation method, we found that the coexistence of the two phenomena may be a reasonable explanation of the observed extra-mixing.

scholarly journals Rotation rates of massive stars in the Magellanic Clouds

2010 ◽  
Vol 6 (S272) ◽  
pp. 38-43
Author(s):  
Laura R. Penny ◽  
Douglas R. Gies
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Evolutionary Models ◽  
Rotation Rates ◽  
Angular Momentum Loss ◽  
Kolmogorov Smirnov ◽  
Statistical Results ◽  
Smirnov Test

AbstractWe present the results of our survey of the projected rotational velocities of 161 O-type stars in the Magellanic Clouds from archival FUSE observations. The evolved and unevolved samples from each environment are compared through the Kolmogorov-Smirnov test to determine if the distribution of equatorial rotational velocities is metallicity dependent for these massive objects. Stellar interior models predict that massive stars with SMC metallicity will have significantly reduced angular momentum loss on the main sequence compared to their Galactic counterparts. Our statistical results find some support for this prediction but also show that even at Galactic metallicity, evolved and unevolved massive stars have fairly similar fractions of stars with large V sin i. What is more compelling are the few evolved objects in the Magellanic Clouds with rotational velocities that approach or even exceed those predicted from the evolutionary models.

Social cognition and brain organization in chimpanzees (Pan troglodytes) and bonobos (Pan paniscus)

2018 ◽  
Author(s):  
William D. Hopkins ◽  
Cheryl D. Stimpson ◽  
Chet C. Sherwood
Keyword(s):  
Social Cognition ◽  
Social Behaviour ◽  
Grey Matter ◽  
Species Differences ◽  
Pan Paniscus ◽  
Grey Matter Volume ◽  
Evolutionary Models ◽  
Brain Organization ◽  
Matter Volume ◽  
Cognition Sociale

Bonobos and chimpanzees are two closely relates species of the genus Pan, yet they exhibit marked differences in anatomy, behaviour and cognition. For this reason, comparative studies on social behaviour, cognition and brain organization between these two species provide important insights into evolutionary models of human origins. This chapter summarizes studies on socio-communicative competencies and social cognition in chimpanzees and bonobos from the authors’ laboratory in comparison to previous reports. Additionally, recent data on species differences and similarities in brain organization in grey matter volume and distribution is presented. Some preliminary findings on microstructural brain organization such as neuropil space and cellular distribution in key neurotransmitters and neuropeptides involved in social behaviour and cognition is presented. Though these studies are in their infancy, the findings point to potentially important differences in brain organization that may underlie bonobo and chimpanzees’ differences in social behaviour, communication and cognition. Les bonobos et les chimpanzés sont deux espèces du genus Pan prochement liées, néanmoins ils montrent des différences anatomiques, comportementales et cognitives marquées. Pour cette raison, les études comparatives sur le comportement social, la cognition et l’organisation corticale entre ces deux espèces fournissent des idées sur les modèles évolutionnaires des origines humaines. Dans ce chapitre, nous résumons des études sur les compétences socio-communicatives et la cognition sociale chez les chimpanzés et les bonobos de notre laboratoire en comparaison avec des rapports précédents. En plus, nous présentons des données récentes sur les différences et similarités d’organisation corticale du volume et distribution de la matière grise entre espèces. Nous présentons plus de résultats préliminaires sur l’organisation corticale microstructurale comme l’espace neuropile et la division cellulaire dans des neurotransmetteurs clés et les neuropeptides impliqués dans le comportement social et la cognition. Bien que ces études sont dans leur enfance, les résultats montrent des différences d’organisation corticale importantes qui sont à la base des différences de comportement social, la communication et la cognition entre les bonobos et les chimpanzés.

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