RADIUS-DEPENDENT ANGULAR MOMENTUM EVOLUTION IN LOW-MASS STARS. I

By A. Reiners, S. Mohanty. 2011

155 citations recorded by the source corpus.

Angular momentum evolution in low-mass stars is determined by initial conditions during star formation, stellar structure evolution, and the behavior of stellar magnetic fields. Here we show that the empirical picture of angular momentum evolution arises naturally if rotation is related to magnetic field strength instead of to magnetic flux and formulate a corrected braking law based on this. Angular momentum evolution then becomes a strong function of stellar radius, explaining the main trends observed in open clusters and field stars at a few Gyr: the steep transition in rotation at the boundary to full convection arises primarily from the large change in radius across this boundary and does not require changes in dynamo mode or field topology. Additionally, the data suggest transient core-envelope decoupling among solar-type stars and field saturation at longer periods in very low mass stars. For solar-type stars, our model is also in good agreement with the empirical Skumanich law. Finally, in further support of the theory, we show that the predicted age at which low-mass stars spin down from the saturated to unsaturated field regimes in our model corresponds remarkably well to the observed lifetime of magnetic activity in these stars.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/62d45ac2d87d9a47585e1add4f1d82f81ac454bd

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In Astronomy and Astrophysics

1. A. Reiners
2. Suzanne Aigrain
3. T. Mazeh
4. D. Charbonneau
5. Laurent Gizon
6. T. Reinhold
7. G. Basri
8. A. McQuillan

In Instrumentation

1. Suzanne Aigrain
2. T. Reinhold
3. Laurent Gizon
4. A. McQuillan
5. A. Reiners
6. T. Mazeh
7. F. Gallet
8. G. Basri

Citations in the corpus

• ROTATION PERIODS OF 34,030 KEPLER MAIN-SEQUENCE STARS: THE FULL AUTOCORRELATION SAMPLE (2014, background): “In recent years there has also been considerable work towards understanding and modeling the underlying physics behind gyrochronology (Reiners & Mohanty 2012; Matt et al. 2012; Gallet & Bouvier 2013, and references therein).”
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, methodology): “As in Vidotto et al. (2013), we compute B? using the parametrization of Reiners & Mohanty (2012) : B?”
• A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone (2013, methodology): “Following the simple models in Reiners & Mohanty (2012), the low activity and the estimate of the rotation period of GJ 667C (P> 100 days, see Section 6) also support an age of> 2 Gyr.”
• Rotation periods of 12 000 main-sequence Kepler stars: Dependence on stellar spectral type and comparison with v sin i observations (2013, background): “Measuring stellar rotation as a function of age and mass is essential to studies of stellar evolution (Maeder 2009) and stellar dynamos (Böhm-Vitense 2007; Reiners & Mohanty 2012).”
• Chromospheric activity catalogue of 4454 cool stars (2018, background): “However, the spin-down rates for cool stars are not expected to change so dramatically for the spectral types of these stars (Reiners & Mohanty 2012).”
• THE MASS-DEPENDENCE OF ANGULAR MOMENTUM EVOLUTION IN SUN-LIKE STARS (2014, background): “…et al. 2012); models for the evolution of stellar spin rate in time (e.g., MacGregor & Brenner 1991; Denissenkov et al. 2010; Scholz et al. 2011; Reiners & Mohanty 2012; Gallet & Bouvier 2013; van Saders & Pinsonneault 2013; Brown 2014); and gyrochronology relations (Barnes 2003, 2010; Mamajek…”
• Observations of Cool-Star Magnetic Fields (2012, background): “Early-M dwarfs appear to suffer much more severe rotational braking so that their activity lifetime is shorter than in later M dwarfs (West et al., 2008), and this can be explained by the severe change in radius and its consequences to angular momentum loss (Reiners and Mohanty, 2011).”
• Improved angular momentum evolution model for solar-like stars II. Exploring the mass dependence (2015, unknown): “…new braking law contrasts with the well-known Kawaler (1988) prescription used in almost all angular momentum evolution models so far (e.g. Bouvier 2008; Irwin & Bouvier 2009; Denissenkov et al. 2010; Spada et al. 2011) as well as with the Kawaler-modified model proposed by Reiners & Mohanty (2012).”
• Rotation and differential rotation of active Kepler stars (2013, methodology): “Ionized material follows the magnetic field lines (stellar wind) and carries away angular momentum resulting in a spin-down of the star (Barnes 2003; Reiners & Mohanty 2012).”
• Rotation and magnetism of Kepler pulsating solar-like stars : Towards asteroseismically calibrated age-rotation relations (2014, background): “Corresponding theoretical work seeks to provide angular momentum loss laws that reproduce the observed spindown (Kawaler 1988; Reiners & Mohanty 2012) and produce the gyrochronology relationship.”
• Improved angular momentum evolution model for solar-like stars (2013, methodology): “A number of models have thus been proposed to account for these new observational results (e.g., Irwin et al. 2007; Bouvier 2008; Denissenkov et al. 2010; Spada et al. 2011; Reiners & Mohanty 2012).”
• Measuring the rotation period distribution of field M dwarfs with Kepler (2013, background): “The latest generation of theoretical models of angular momentum loss via a magnetised wind (Reiners & Mohanty 2012) naturally explains the wide range of rotation rates observed for M-dwarfs in early mainsequence clusters.”