scholarly journals Lithium depletion and angular momentum transport in F-type and G-type stars in Galactic open clusters

2021 ◽  
Author(s):  
T. Dumont ◽  
C. Charbonnel ◽  
A. Palacios ◽  
S. Borisov
Keyword(s):  
Angular Momentum ◽  
Open Clusters ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Lithium Depletion

scholarly journals First grids of low-mass stellar models and isochrones with self-consistent treatment of rotation

2019 ◽  
Vol 631 ◽  
pp. A77 ◽  
Author(s):  
L. Amard ◽  
A. Palacios ◽  
C. Charbonnel ◽  
F. Gallet ◽  
C. Georgy ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Open Clusters ◽  
Momentum Transport ◽  
Surface Boundary ◽  
Angular Momentum Transport ◽  
Solar Composition ◽  
Self Consistent ◽  
Low Mass ◽  
Stellar Models ◽  
The Impact

Aims.We present an extended grid of state-of-the art stellar models for low-mass stars including updated physics (nuclear reaction rates, surface boundary condition, mass-loss rate, angular momentum transport, rotation-induced mixing, and torque prescriptions). We evaluate the impact of wind braking, realistic atmospheric treatment, rotation, and rotation-induced mixing on the structural and rotational evolution from the pre-main sequence (PMS) to the turn-off.Methods.Using the STAREVOL code, we provide an updated PMS grid. We computed stellar models for seven different metallicities, from [Fe/H] = −1 dex to [Fe/H] = +0.3 dex with a solar composition corresponding toZ = 0.0134. The initial stellar mass ranges from 0.2 to 1.5M⊙with extra grid refinement around one solar mass. We also provide rotating models for three different initial rotation rates (slow, median, and fast) with prescriptions for the wind braking and disc-coupling timescale calibrated on observed properties of young open clusters. The rotational mixing includes the most recent description of the turbulence anisotropy in stably stratified regions.Results.The overall behaviour of our models at solar metallicity, and their constitutive physics, are validated through a detailed comparison with a variety of distributed evolutionary tracks. The main differences arise from the choice of surface boundary conditions and initial solar composition. The models including rotation with our prescription for angular momentum extraction and self-consistent formalism for angular momentum transport are able to reproduce the rotation period distribution observed in young open clusters over a wide range of mass values. These models are publicly available and can be used to analyse data coming from present and forthcoming asteroseismic and spectroscopic surveys such asGaia, TESS, and PLATO.

scholarly journals Lithium depletion and angular momentum transport in solar-type stars

2020 ◽  
Author(s):  
T. Dumont ◽  
A. Palacios ◽  
C. Charbonnel ◽  
O. Richard ◽  
L. Amard ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Solar Type ◽  
Lithium Depletion

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 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.

scholarly journals Angular Momentum Transport and Dynamo Effect in Kepler Disks

2001 ◽  
Vol 200 ◽  
pp. 410-414
Author(s):  
Günther Rüdiger ◽  
Udo Ziegler
Keyword(s):  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Spherical Model ◽  
Momentum Transport ◽  
Rotational Instability ◽  
Jet Formation ◽  
Angular Momentum Transport ◽  
Dynamo Effect ◽  
Background Shear

Properties have been demonstrated of the magneto-rotational instability for two different applications, i.e. for a global spherical model and a box simulation with Keplerian background shear flow. In both nonlinear cases a dynamo operates with a negative (positive) α-effect in the northern (southern) disk hemisphere and in both cases the angular momentum transport is outwards. Keplerian accretion disks should therefore exhibit large-scale magnetic fields with a dipolar geometry of the poloidal components favoring jet formation.

scholarly journals Magnetic field transport in compact binaries

2020 ◽  
Vol 641 ◽  
pp. A133
Author(s):  
N. Scepi ◽  
G. Lesur ◽  
G. Dubus ◽  
J. Jacquemin-Ide
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Magnetic Flux ◽  
Large Scale ◽  
Compact Object ◽  
Light Curves ◽  
Momentum Transport ◽  
Local Magnetization ◽  
Angular Momentum Transport ◽  
The Impact

Context. Dwarf novæ (DNe) and low mass X-ray binaries (LMXBs) show eruptions that are thought to be due to a thermal-viscous instability in their accretion disk. These eruptions provide constraints on angular momentum transport mechanisms. Aims. We explore the idea that angular momentum transport could be controlled by the dynamical evolution of the large-scale magnetic field. We study the impact of different prescriptions for the magnetic field evolution on the dynamics of the disk. This is a first step in confronting the theory of magnetic field transport with observations. Methods. We developed a version of the disk instability model that evolves the density, the temperature, and the large-scale vertical magnetic flux simultaneously. We took into account the accretion driven by turbulence or by a magnetized outflow with prescriptions taken, respectively, from shearing box simulations or self-similar solutions of magnetized outflows. To evolve the magnetic flux, we used a toy model with physically motivated prescriptions that depend mainly on the local magnetization β, where β is the ratio of thermal pressure to magnetic pressure. Results. We find that allowing magnetic flux to be advected inwards provides the best agreement with DNe light curves. This leads to a hybrid configuration with an inner magnetized disk, driven by angular momentum losses to an MHD outflow, sharply transiting to an outer weakly-magnetized turbulent disk where the eruptions are triggered. The dynamical impact is equivalent to truncating a viscous disk so that it does not extend down to the compact object, with the truncation radius dependent on the magnetic flux and evolving as Ṁ−2/3. Conclusions. Models of DNe and LMXB light curves typically require the outer, viscous disk to be truncated in order to match the observations. There is no generic explanation for this truncation. We propose that it is a natural outcome of the presence of large-scale magnetic fields in both DNe and LMXBs, with the magnetic flux accumulating towards the center to produce a magnetized disk with a fast accretion timescale.

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