Towards a unified model of stellar rotation - II. Model-dependent characteristics of stellar populations

Potter, Adrian T.; Tout, Christopher A.; Brott, I.

doi:10.1111/j.1365-2966.2012.20952.x

Cited by 18 publications

(21 citation statements)

References 23 publications

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“…binary merger, mass transfer or common evelope evolution (Ferrario et al 2009;Langer 2012). Finally, the fields could be generated by a dynamo process inside the the main sequence star (Spruit 2002;Potter et al 2012b). We emphasize that these three alternatives predict different time-dependances of the stellar rotation and magnetic field incidence, which might be testable if the age distribution of our sample stars can be established.…”

Section: Magnetic Fieldsmentioning

confidence: 99%

“…It may affect both how the star evolves during hydrogen core burning (see, for example, Brott et al 2011;Potter et al 2012b) and the nature of any supernova explosion (see, for example Woosley & Heger 2006;Yoon et al 2006). It can also provide insights into other phenomena such as star formation Tables 3 and 4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/550/A109 Hubble Fellow.…”

Section: Introductionmentioning

confidence: 99%

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The VLT-FLAMES Tarantula Survey

Dufton

Langer

Dunstall

et al. 2013

A&A

142

222

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Aims. Projected rotational velocities (v e sin i) have been estimated for 334 targets in the VLT-FLAMES Tarantula Survey that do not manifest significant radial velocity variations and are not supergiants. They have spectral types from approximately O9.5 to B3. The estimates have been analysed to infer the underlying rotational velocity distribution, which is critical for understanding the evolution of massive stars. Methods. Projected rotational velocities were deduced from the Fourier transforms of spectral lines, with upper limits also being obtained from profile fitting. For the narrower lined stars, metal and non-diffuse helium lines were adopted, and for the broader lined stars, both non-diffuse and diffuse helium lines; the estimates obtained using the different sets of lines are in good agreement. The uncertainty in the mean estimates is typically 4% for most targets. The iterative deconvolution procedure of Lucy has been used to deduce the probability density distribution of the rotational velocities. Results. Projected rotational velocities range up to approximately 450 km s −1 and show a bi-modal structure. This is also present in the inferred rotational velocity distribution with 25% of the sample having 0 ≤ v e ≤ 100 km s −1 and the high velocity component having v e ∼ 250 km s −1 . There is no evidence from the spatial and radial velocity distributions of the two components that they represent either field and cluster populations or different episodes of star formation. Be-type stars have also been identified. Conclusions. The bi-modal rotational velocity distribution in our sample resembles that found for late-B and early-A type stars. While magnetic braking appears to be a possible mechanism for producing the low-velocity component, we can not rule out alternative explanations.

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Section: Magnetic Fieldsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The VLT-FLAMES Tarantula Survey

Dufton

Langer

Dunstall

et al. 2013

A&A

142

222

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“…For example, synthetic stellar populations computed by Brott et al (2011) andPotter et al (2012) cannot reproduce several groups of stars observed by Hunter et al (2009), notably nitrogen-rich slow rotators. Note that the existence of these stars might be explained by rotational mixing if some braking is active at the surface, for instance due to a surface magnetic field (Meynet et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Shear mixing in stellar radiative zones

Prat

Guilet

Viallet

et al. 2016

A&A

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Context. Recent numerical simulations suggest that the model by Zahn (1992, A&A, 265, 115) for the turbulent mixing of chemical elements due to differential rotation in stellar radiative zones is valid. Aims. We investigate the robustness of this result with respect to the numerical configuration and Reynolds number of the flow. Methods. We compare results from simulations performed with two different numerical codes, including one that uses the shearingbox formalism. We also extensively study the dependence of the turbulent diffusion coefficient on the turbulent Reynolds number. Results. The two numerical codes used in this study give consistent results. The turbulent diffusion coefficient is independent of the size of the numerical domain if at least three large turbulent structures fit in the box. Generally, the turbulent diffusion coefficient depends on the turbulent Reynolds number. However, our simulations suggest that an asymptotic regime is obtained when the turbulent Reynolds number is larger than 10 3 . Conclusions. Shear mixing in the regime of small Péclet numbers can be investigated numerically both with shearing-box simulations and simulations using explicit forcing. Our results suggest that Zahn's model is valid at large turbulent Reynolds numbers.

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“…Thanks to the progress in the computational efficiency of such codes, it is now possible to compute entire synthetic stellar populations from a given distribution of initial conditions that include chemical composition and angular momentum. As shown by Brott et al (2011) and Potter et al (2012), these synthetic populations can be compared to observed ones, such as those obtained by large surveys. In particular, the authors recover the main group of stars observed by Hunter et al (2009).…”

Section: Introductionmentioning

confidence: 99%

Shear mixing in stellar radiative zones

Prat

Lignières

2014

A&A

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Context. Turbulent transport of chemical elements in radiative zones of stars is considered in current stellar evolution codes thanks to phenomenologically derived diffusion coefficients. Recent local numerical simulations suggest that the coefficient for radial turbulent diffusion due to radial differential rotation satisfies D t 0.058κ/Ri, in qualitative agreement with the model of Zahn (1992, A&A, 265, 115). However, this model does not apply (i) when differential rotation is strong with respect to stable thermal stratification or (ii) when chemical stratification has a significant dynamical effect, a situation encountered at the outer boundary of nuclear-burning convective cores. Aims. We extend our numerical study to consider the effects of chemical stratification and of strong shear, and compare the results with prescriptions used in stellar evolution codes. Methods. We performed local, direct numerical simulations of stably stratified, homogeneous, sheared turbulence in the Boussinesq approximation. The regime of high thermal diffusivities, typical of stellar radiative zones, is reached thanks to the so-called smallPéclet-number approximation, which is an asymptotic development of the Boussinesq equations in this regime. The dependence of the diffusion coefficient on chemical stratification was explored in this approximation. Results. Maeder's extension of Zahn's model in the strong-shear regime (Maeder 1995, A&A, 299, 84) is not supported by our results, which are better described by a model found in the geophysical literature. As regards the effect of chemical stratification, our quantitative estimate of the diffusion coefficient as a function of the mean gradient of mean molecular weight leads to the formula D t 0.45κ(0.12 − Ri µ )/Ri, which is compatible in the weak-shear regime with the model of Maeder & Meynet (1996, A&A, 313, 140) but not with Maeder's (1997, A&A, 321, 134).

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Towards a unified model of stellar rotation - II. Model-dependent characteristics of stellar populations

Cited by 18 publications

References 23 publications

The VLT-FLAMES Tarantula Survey

The VLT-FLAMES Tarantula Survey

Shear mixing in stellar radiative zones

Shear mixing in stellar radiative zones

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