The Monitor project: rotation of low-mass stars in the open cluster NGC 2516

Irwin, Jonathan; Hodgkin, S. T.; Aigrain, S.; Hebb, Leslie; Bouvier, J.; Clarke, C. J.; Moraux, E.; Bramich, D. M.

doi:10.1111/j.1365-2966.2007.11640.x

Cited by 131 publications

(206 citation statements)

References 76 publications

(131 reference statements)

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“…Estimates of the timescale for coreenvelope coupling in solar-type stars range from about 1 Myr for the fastest rotators up to 10−100 Myr (e.g. Keppens et al 1995;Alain 1998) and 0.5 Gyr (Irwin et al 2007) for slowly rotating stars. Models of rotational evolution of solar-type stars with angular momentum transport described as a purely diffusive process show that these coupling time intervals correspond to large diffusion coefficients that would lead to rates of surface Li destruction strongly exceeding the trend observed in the Sun and its twins .…”

Section: Discussionmentioning

confidence: 99%

“…Photometric monitoring programs have produced a large number of measurements of this kind in young open clusters (e.g. Prosser et al 1995;Krishnamurthi et al 1998;Irwin et al 2007;Collier Cameron et al 2009;Hartman et al 2009Hartman et al , 2010. Based on these data, Barnes (2003a) found that young stars tend to group into two main sub-populations that lie on narrow sequences in diagrams where the measured rotation periods of the members of a stellar cluster are plotted against their B − V colour indices.…”

Section: Introductionmentioning

confidence: 99%

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X-ray emission regimes and rotation sequences in M 35

Gondoin

2013

A&A

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Context. Late-type stars in young open clusters show two kinds of dependence of their X-ray emission on rotation. They also tend to group into two main sub-populations that lie on narrow sequences in diagrams where their rotation periods are plotted against their (B − V) colour indices. A correlation between these two regimes of X-ray emission and the rotation sequences has been recently observed in the M 34 open cluster. Sun-like M 34 stars also show a drop of their X-ray to bolometric luminosity ratio by about one order of magnitude at a Rossby number of about 0.3. Aims. The present study looks for similar connections between X-ray activity and rotation in an other open cluster. The aim is to consolidate a model of X-ray activity evolution on the main sequence and to provide observational constraints on dynamo processes in the interiors of late-type stars. Methods. The paper compares XMM-Newton measurements of X-ray stellar emission in M 35 with X-ray luminosity distributions derived from rotation period measurements assuming either an X-ray regime transition at a critical Rossby number or a correlation between X-ray emission regimes and rotation sequences. Results. This second hypothesis could account for the low number of M 35 stars detected in X-rays. A model of X-ray activity evolution is proposed based on the correlation. One major output is that the transition from saturated to non-saturated X-ray emission occurs at Rossby numbers between about 0.13 and 0.4 for each star depending on its mass and initial period of rotation on the ZAMS. This prediction agrees with observations of stellar X-ray emission in M 34. It explains the large range of X-ray luminosities observed among Sun-like stars in young open clusters. Conclusions. I conclude that the correlation between X-ray emission regimes and rotation sequences could be a fundamental property of the early evolution of stellar magnetic activity on the main sequence. I argue that the angular momentum redistribution mechanism(s) responsible for the transition between rotation sequences could result in a changing mixture of dynamo processes occurring side by side, possibly including a turbulent dynamo at high rotation rate and an interface-type dynamo whose efficiency decreases progressively at later stage of stellar evolution when rotation dies away.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

X-ray emission regimes and rotation sequences in M 35

Gondoin

2013

A&A

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“…These new observational results provide extremely useful guidance for the modelling of angular momentum evolution of low-mass stars (M * < 1.2 M ) from 1 Myr to 10 Gyr (e.g. Irwin et al 2007;Bouvier 2008;Denissenkov et al 2010;Spada et al 2011;Reiners & Mohanty 2012;Gallet & Bouvier 2013) and offer a unique insight into the physical processes that dictate rotational evolution. To account for the observations, parametric models have to incorporate at least three major processes: the star-disk interaction during the early pre-main sequence (PMS; Matt & Pudritz 2005b;Zanni & Ferreira 2009Ferreira et al 2000;Matt et al 2010), the loss of angular momentum through powerful stellar winds on the early main sequence (MS; Weber & Davis 1967;Kawaler 1988;Matt & Pudritz 2005a;Vidotto et al 2011Vidotto et al , 2014bZanni & Ferreira 2011;Cranmer & Saar 2011;Matt et al 2012a,b;Reiners & Mohanty 2012;Réville et al 2015), and the redistribution of angular momentum in the stellar interior at all phases of evolution (MacGregor & Brenner 1991;Allain 1998;Palacios et al 2003Palacios et al , 2006Charbonnel & Lagarde 2010;Lagarde et al 2011Lagarde et al , 2012Charbonnel et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Improved angular momentum evolution model for solar-like stars

Gallet

Bouvier

2015

A&A

231

290

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Context. Understanding the physical processes that dictate the angular momentum evolution of solar-type stars from birth to maturity remains a challenge for stellar physics. Aims. We aim to account for the observed rotational evolution of low-mass stars over the age range from 1 Myr to 10 Gyr. Methods. We developed angular momentum evolution models for 0.5 and 0.8 M stars. The parametric models include a new wind braking law based on recent numerical simulations of magnetised stellar winds, specific dynamo and mass-loss rate prescriptions, as well as core-envelope decoupling. We compare model predictions to the distributions of rotational periods measured for low-mass stars belonging to star-forming regions and young open clusters. Furthermore, we explore the mass dependence of model parameters by comparing these new models to the solar-mass models we developed earlier.Results. Rotational evolution models are computed for slow, median, and fast rotators at each stellar mass. The models reproduce reasonably well the rotational behaviour of low-mass stars between 1 Myr and 8−10 Gyr, including pre-main sequence to zero-age main sequence spin up, prompt zero-age main sequence spin down, and early-main sequence convergence of the surface rotation rates. Fast rotators are found to have systematically shorter disk lifetimes than moderate and slow rotators, thus enabling dramatic pre-main sequence spin up. They also have shorter core-envelope coupling timescales, i.e., more uniform internal rotation. As for the mass dependence, lower mass stars require significantly longer core-envelope coupling timescales than solar-type stars, which results in strong differential rotation developing in the stellar interior on the early main sequence. Lower mass stars also require a weaker braking torque to account for their longer spin-down timescale on the early main sequence, while they ultimately converge towards lower rotational velocities than solar-type stars in the longer term because of their reduced moment of inertia. We also find evidence that the mass dependence of the wind braking efficiency may be related to a change in the magnetic topology in lower mass stars. Conclusions. We have included in parametric models the main physical processes that dictate the angular momentum evolution of low-mass stars. The models suggest that these processes are quite sensitive to both mass and instantaneous rotation rate. We have worked out and reported here the main trends of these mass and rotation dependencies, whose origin still have to be addressed through a detailed modelling of magnetised stellar winds, internal angular momentum transport processes, and protoplanetary disk dissipation mechanisms.

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“…Observations of rotational periods for young solar-type stars in open clusters suggest that slow rotators develop a high degree of differential rotation between the radiative core and the convective envelope, while solid-body rotation is favoured for fast rotators (Irwin et al 2007;Bouvier 2008;Denissenkov et al 2010;Denissenkov 2010). Models including a detailed treatment of shellular rotation show however that meridional circulation and shear mixing alone do not couple the core and envelope, even in the presence of rapid rotation (Eggenberger et al 2010a).…”

Section: Introductionmentioning

confidence: 99%

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

Eggenberger

Montalbán

Miglio

2012

A&A

221

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Context. Recent asteroseismic observations have led to the determination of rotational frequency splittings for ℓ = 1 mixed modes in red giants. Aims. We investigate how these observed splittings can constrain the modelling of the physical processes transporting angular momentum in stellar interiors. Methods. We first compare models including a comprehensive treatment of shellular rotation only, with the rotational splittings observed for the red giant KIC 8366239. We then study how these asteroseismic constraints can give us information about the efficiency of an additional mechanism for the internal transport of angular momentum. This is done by computing rotating models of KIC 8366239 that include a constant viscosity corresponding to this physical process, in addition to the treatment of shellular rotation. Results. We find that models of red giant stars including shellular rotation only predict steep rotation profiles, which are incompatible with the measurements of rotational splittings in the red giant KIC 8366239. Meridional circulation and shear mixing alone are found to produce an insufficient internal coupling so that an additional mechanism for the internal transport of angular momentum is needed during the post-main sequence evolution. We show that the viscosity ν add corresponding to this mechanism is strongly constrained to be ν add = 3 × 10 4 cm 2 s −1 thanks to the observed ratio of the splittings for modes in the wings to those at the centre of the dipole forests. Such a value of viscosity may suggest that the same unknown physical process is at work during the main sequence and the post-main sequence evolution.

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The Monitor project: rotation of low-mass stars in the open cluster NGC 2516

Cited by 131 publications

References 76 publications

X-ray emission regimes and rotation sequences in M 35

X-ray emission regimes and rotation sequences in M 35

Improved angular momentum evolution model for solar-like stars

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

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