The Evolution of Rotation and Activity in Young Open Clusters: IC 2391

Patten, B. M.; Simon, Theodore

doi:10.1086/192346

Cited by 149 publications

(271 citation statements)

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“…The dependence of the X-ray luminosity relative to the bolometric luminosity on the Rossby number was confirmed for F5 through M5 main-sequence stars using both clusters and field stars (e.g. Patten & Simon 1996;Randich et al 2000).…”

Section: Notesmentioning

confidence: 85%

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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: Notesmentioning

confidence: 85%

“…The X-ray emission from late-type stars in open clusters exhibits two kinds of dependences on stellar rotation (e.g. Patten & Simon 1996;Randich 2000;Feigelson et al 2003;Pizzolato et al 2003). Fast rotators show a relatively constant X-ray to bolometric luminosity ratio at the so-called (L X /L bol ) ≈ 10 −3 saturation level.…”

Section: Introductionmentioning

confidence: 99%

X-ray emission regimes and rotation sequences in M 35

Gondoin

2013

A&A

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“…Both chromospheric activity indicators and X-ray studies, furthermore, can be used as proxies for measurements of the strength of stellar magnetic fields. There is now extensive empirical evidence that both chromospheric and coronal indicators become independent of the rotation rate above a mass-dependent critical angular velocity (e.g., Patten & Simon 1996); this would imply a much lower angular momentum loss rate for rapid rotators. We note that this does not contradict the overall Weber & Davis (1967) model in the case of slow rotators; however, all of the direct and indirect observational tests in low-mass stars and open clusters of different ages indicates that it overestimates the angular momentum loss rate for rotation periods shorter than 2.5-5 days.…”

Section: Angular Momentum Lossmentioning

confidence: 99%

Cataclysmic Variables: An Empirical Angular Momentum Loss Prescription from Open Cluster Data

Andronov

Pinsonneault

Sills

2003

ApJ

123

165

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We apply the angular momentum loss rates inferred from open cluster stars to the evolution of cataclysmic variables (CVs). We show that the angular momentum prescriptions used in earlier CV studies are inconsistent with the measured rotation data in open clusters. The timescale for angular momentum loss ( _ J J) above the fully convective boundary is $2 orders of magnitude longer than inferred from the older model, and the observed angular momentum loss properties show no evidence for a change in behavior at the fully convective boundary. This provides evidence against the hypothesis that the period gap is caused by an abrupt change in the angular momentum loss law when the secondary becomes fully convective. Furthermore, the empirical angular momentum loss law implies a timescale for CV evolution that is comparable to a Hubble time; for the same reason, it will be more difficult to produce CVs from the products of common envelope evolution, and it implies a lower space density of CVs. The predicted loss rate for short-period CVs is consistent with the observed period minimum (1.3 hr). We infer the time-averaged mass accretion rate and derive the mass-period relation for different evolutionary states of the secondary. The steady-state accretion rates are significantly lower than the claimed observational rates; we discuss some possible explanations. The mass-period relationship is more consistent with evolved secondaries than with unevolved secondaries above the period gap. Implications for the CV period gap are discussed, including the possibility that two populations of secondaries could produce the gap.

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“…There is a wide spread of rotational velocities among any given population of very young early-G (solar-type) stars [Stauffer and Soderblom, 1991;Patten and Simon, 1996]. However, the angular momentum loss mechanism appears to operate in such a way that the broad distribution of spins at age 50-70 Myr (as in the young galactic clusters a Persei and the Pleiades) is funneled into a much narrower distribution at age •600 Myr (as in the nearby Hyades cluster) [Stauffer and Hartmann, 1987 It is convenient to separate calculation of the time history of solar-induced photoionization into four moreor-less independent parts.…”

Section: Rotational Convergence Effectmentioning

confidence: 99%