scholarly journals Angular momentum transport in stellar interiors constrained by rotational splittings of mixed modes in red giants

2012 ◽  
Vol 544 ◽  
pp. L4 ◽  
Author(s):  
P. Eggenberger ◽  
J. Montalbán ◽  
A. Miglio
Keyword(s):  
Angular Momentum ◽  
Momentum Transport ◽  
Red Giants ◽  
Angular Momentum Transport ◽  
Stellar Interiors ◽  
Mixed Modes

scholarly journals Asteroseismology of red giants to constrain angular momentum transport

2014 ◽  
Vol 9 (S307) ◽  
pp. 165-170
Author(s):  
P. Eggenberger
Keyword(s):  
Angular Momentum ◽  
Rotational Frequency ◽  
Momentum Transport ◽  
Red Giants ◽  
Angular Momentum Transport ◽  
Rotation Rates ◽  
Giant Stars ◽  
Red Giant ◽  
Core Rotation

AbstractAsteroseismic data obtained by theKeplerspacecraft have led to the recent detection and characterization of rotational frequency splittings of mixed modes in red-giant stars. This has opened the way to the determination of the core rotation rates for these stars, which is of prime importance to progress in our understanding of internal angular momentum transport. In this contribution, we discuss which constraints can be brought by these asteroseismic measurements on the modelling of angular momentum transport in stellar radiative zones.

scholarly journals Transport of angular momentum in solar-like oscillating stars

2013 ◽  
Vol 9 (S301) ◽  
pp. 161-168
Author(s):  
Mariejo Goupil ◽  
Sébastien Deheuvels ◽  
Joao Marques ◽  
Yveline Lebreton ◽  
Benoit Mosser ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Space Missions ◽  
Momentum Transport ◽  
Current Understanding ◽  
Red Giants ◽  
The Sun ◽  
Low Mass Stars ◽  
Angular Momentum Transport ◽  
Low Mass

AbstractOur current understanding and modeling of angular momentum transport in low-mass stars are briefly reviewed. Emphasis is set on single stars slightly younger that the Sun and on subgiants and red giants observed by the space missionsCoRoTandKepler.

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
Keyword(s):  
Angular Momentum ◽  
Gravity Waves ◽  
Stellar Evolution ◽  
Transport Processes ◽  
Momentum Transport ◽  
Critical Layer ◽  
Secondary Source ◽  
Angular Momentum Transport ◽  
Critical Layers ◽  
Stellar Interiors

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.

scholarly journals Constraining the efficiency of angular momentum transport with asteroseismology of red giants: the effect of stellar mass

2017 ◽  
Vol 599 ◽  
pp. A18 ◽  
Author(s):  
P. Eggenberger ◽  
N. Lagarde ◽  
A. Miglio ◽  
J. Montalbán ◽  
S. Ekström ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Stellar Mass ◽  
Momentum Transport ◽  
Red Giants ◽  
Angular Momentum Transport

scholarly journals Seismic evidence for near solid-body rotation in two Kepler subgiants and implications for angular momentum transport

2020 ◽  
Vol 641 ◽  
pp. A117 ◽  
Author(s):  
S. Deheuvels ◽  
J. Ballot ◽  
P. Eggenberger ◽  
F. Spada ◽  
A. Noll ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Internal Rotation ◽  
Open Clusters ◽  
Momentum Transport ◽  
Inversion Method ◽  
Red Giants ◽  
Data Set ◽  
Angular Momentum Transport ◽  
The Core ◽  
Red Giant

Context. Asteroseismic measurements of the internal rotation of subgiants and red giants all show the need for invoking a more efficient transport of angular momentum than theoretically predicted. Constraints on the core rotation rate are available starting from the base of the red giant branch (RGB) and we are still lacking information on the internal rotation of less evolved subgiants. Aims. We identify two young Kepler subgiants, KIC 8524425 and KIC 5955122, whose mixed modes are clearly split by rotation. We aim to probe their internal rotation profile and assess the efficiency of the angular momentum transport during this phase of the evolution. Methods. Using the full Kepler data set, we extracted the mode frequencies and rotational splittings for the two stars using a Bayesian approach. We then performed a detailed seismic modeling of both targets and used the rotational kernels to invert their internal rotation profiles using the MOLA inversion method. We thus obtained estimates of the average rotation rates in the g-mode cavity (⟨Ω⟩g) and in the p-mode cavity (⟨Ω⟩p). Results. We found that both stars are rotating nearly as solid bodies, with core-envelope contrasts of ⟨Ω⟩g/⟨Ω⟩p = 0.68 ± 0.47 for KIC 8524425 and ⟨Ω⟩g/⟨Ω⟩p = 0.72 ± 0.37 for KIC 5955122. This result shows that the internal transport of angular momentum has to occur faster than the timescale at which differential rotation is forced in these stars (between 300 Myr and 600 Myr). By modeling the additional transport of angular momentum as a diffusive process with a constant viscosity νadd, we found that values of νadd >  5 × 104 cm2 s−1 are required to account for the internal rotation of KIC 8524425, and νadd >  1.5 × 105 cm2 s−1 for KIC 5955122. These values are lower than or comparable to the efficiency of the core-envelope coupling during the main sequence, as given by the surface rotation of stars in open clusters. On the other hand, they are higher than the viscosity needed to reproduce the rotation of subgiants near the base of the RGB. Conclusions. Our results yield further evidence that the efficiency of the internal redistribution of angular momentum decreases during the subgiant phase. We thus bring new constraints that will need to be accounted for by mechanisms that are proposed as candidates for angular momentum transport in subgiants and red giants.

scholarly journals Understanding angular momentum transport in red giants: the case of KIC 7341231

2013 ◽  
Vol 555 ◽  
pp. A54 ◽  
Author(s):  
T. Ceillier ◽  
P. Eggenberger ◽  
R. A. García ◽  
S. Mathis
Keyword(s):  
Angular Momentum ◽  
Momentum Transport ◽  
Red Giants ◽  
Angular Momentum Transport

scholarly journals Rotation rate of the solar core as a key constraint to magnetic angular momentum transport in stellar interiors

2019 ◽  
Vol 626 ◽  
pp. L1 ◽  
Author(s):  
P. Eggenberger ◽  
G. Buldgen ◽  
S. J. A. J. Salmon
Keyword(s):  
Angular Momentum ◽  
Rotation Rate ◽  
Open Clusters ◽  
Momentum Transport ◽  
The Sun ◽  
Angular Momentum Transport ◽  
Chemical Gradients ◽  
The Core ◽  
Stellar Interiors ◽  
Core Rotation

Context. The internal rotation of the Sun constitutes a fundamental constraint when modelling angular momentum transport in stellar interiors. In addition to the more external regions of the solar radiative zone probed by pressure modes, measurements of rotational splittings of gravity modes would offer an invaluable constraint on the rotation of the solar core. Aims. We study the constraints that a measurement of the core rotation rate of the Sun could bring on magnetic angular momentum transport in stellar radiative zones. Methods. Solar models accounting for angular momentum transport by hydrodynamic and magnetic instabilities were computed for different initial velocities and disc lifetimes on the pre-main sequence to reproduce the surface rotation velocities observed for solar-type stars in open clusters. The internal rotation of these solar models was then compared to helioseismic measurements. Results. We first show that models computed with angular momentum transport by magnetic instabilities and a recent prescription for the braking of the stellar surface by magnetized winds can reproduce the observations of surface velocities of stars in open clusters. These solar models predict both a flat rotation profile in the external part of the solar radiative zone probed by pressure modes and an increase in the rotation rate in the solar core, where the stabilizing effect of chemical gradients plays a key role. A rapid rotation of the core of the Sun, as suggested by reported detections of gravity modes, is thus found to be compatible with angular momentum transport by magnetic instabilities. Moreover, we show that the efficiency of magnetic angular momentum transport in regions of strong chemical gradients can be calibrated by the solar core rotation rate independently from the unknown rotational history of the Sun. In particular, we find that a recent revised prescription for the transport of angular momentum by the Tayler instability can be easily distinguished from the original Tayler–Spruit dynamo, with a faster rotating solar core supporting the original prescription. Conclusions. By calibrating the efficiency of magnetic angular momentum transport in regions of strong chemical gradients, a determination of the solar core rotation rate through gravity modes is of prime relevance not only for the Sun, but for stars in general, since radial differential rotation precisely develops in these regions during the more advanced stages of evolution.

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