scholarly journals Corotation resonances for gravity waves and their impact on angular momentum transport in stellar interiors

2013 ◽  
Vol 9 (S301) ◽  
pp. 377-378
Author(s):  
Lucie Alvan ◽  
Stéphane Mathis ◽  
Thibaut Decressin

AbstractGravity waves, which propagate in radiation zones, can extract or deposit angular momentum by radiative and viscous damping. Another process, poorly explored in stellar physics, concerns their direct interaction with the differential rotation and the related turbulence. In this work, we thus study their corotation resonances, also called critical layers, that occur where the Doppler-shifted frequency of the wave approaches zero. First, we study the adiabatic and non-adiabatic propagation of gravity waves near critical layers. Next, we derive the induced transport of angular momentum. Finally, we use the dynamical stellar evolution code STAREVOL to apply the results to the case of a solar-like star. The results depend on the value of the Richardson number at the critical layer. In the first stable case, the wave is damped. In the other unstable and turbulent case, the wave can be reflected and transmitted by the critical layer with a coefficient larger than one: the critical layer acts as a secondary source of excitation for gravity waves. These new results can have a strong impact on our understanding of angular momentum transport processes in stellar interiors along stellar evolution where strong gradients of angular velocity can develop.

2010 ◽  
Vol 6 (S272) ◽  
pp. 73-78
Author(s):  
Adrian T. Potter ◽  
Christopher A. Tout

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.


2006 ◽  
Vol 653 (1) ◽  
pp. 756-764 ◽  
Author(s):  
Tamara M. Rogers ◽  
Gary A. Glatzmaier

2020 ◽  
Vol 634 ◽  
pp. L16 ◽  
Author(s):  
J. W. den Hartogh ◽  
P. Eggenberger ◽  
S. Deheuvels

Context. The internal characteristics of stars, such as their core rotation rates, are obtained via asteroseismic observations. A comparison of core rotation rates found in this way with core rotation rates as predicted by stellar evolution models demonstrate a large discrepancy. This means that there must be a process of angular momentum transport missing in the current theory of stellar evolution. A new formalism was recently proposed to fill in for this missing process, which has the Tayler instability as its starting point (by Fuller et al. 2019, MNRAS, 485, 3661, hereafter referred to as “Fuller-formalism”). Aims. We investigate the effect of the Fuller-formalism on the internal rotation of stellar models with an initial mass of 2.5 M⊙. Methods. Stellar evolution models, including the Fuller-formalism, of intermediate-mass stars were calculated to make a comparison between asteroseismically obtained core rotation rates in the core He burning phase and in the white dwarf phase. Results. Our main results show that models including the Fuller-formalism can match the core rotation rates obtained for the core He burning phases. However, these models are unable to match the rotation rates obtained for white dwarfs. When we exclude the Fuller-formalism at the end of the core He burning phase, the white dwarf rotation rates of the models match the observed rates. Conclusions. We conclude that in the present form, the Fuller-formalism cannot be the sole solution for the missing process of angular momentum transport in intermediate-mass stars.


2013 ◽  
Vol 772 (1) ◽  
pp. 21 ◽  
Author(s):  
T. M. Rogers ◽  
D. N. C. Lin ◽  
J. N. McElwaine ◽  
H. H. B. Lau

2019 ◽  
Vol 622 ◽  
pp. A187 ◽  
Author(s):  
J. W. den Hartogh ◽  
P. Eggenberger ◽  
R. Hirschi

Context. Transport of angular momentum has been a challenging topic within the stellar evolution community, even more since the recent asteroseismic surveys. All published studies on rotation using asteroseismic observations show a discrepancy between the observed and calculated rotation rates, indicating there is an undetermined process of angular momentum transport active in these stars. Aims. We aim to constrain the efficiency of this process by investigating rotation rates of 2.5 M⊙ stars. Methods. First, we investigated whether the Tayler-Spruit dynamo could be responsible for the extra transport of angular momentum for stars with an initial mass of 2.5 M⊙. Then, by computing rotating models including a constant additional artificial viscosity, we determined the efficiency of the missing process of angular momentum transport by comparing the models to the asteroseismic observations of core helium burning stars. Parameter studies were performed to investigate the effect of the stellar evolution code used, initial mass, and evolutionary stage. We evolved our models into the white dwarf phase, and provide a comparison to white dwarf rotation rates. Results. The Tayler-Spruit dynamo is unable to provide enough transport of angular momentum to reach the observed values of the core helium burning stars investigated in this paper. We find that a value for the additional artificial viscosity νadd around 107 cm2 s−1 provides enough transport of angular momentum. However, the rotational period of these models is too high in the white dwarf phase to match the white dwarf observations. From this comparison we infer that the efficiency of the missing process must decrease during the core helium burning phase. When excluding the νadd during core helium burning phase, we can match the rotational periods of both the core helium burning stars and white dwarfs.


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