Using the Galactic Dynamics of M7 Dwarfs to Infer the Evolution of Their Magnetic Activity

Abstract

We present a spectroscopic study and dynamical analysis of ~2600 M7 dwarfs. We confirm our previous finding that the fraction of magnetically active stars decreases with vertical distance from the Galactic plane. We also show that the mean luminosity of the H-alpha emission has a small but statistically significant decrease with distance. Using space motions for ~1300 stars and a simple one-dimensional dynamical simulation, we demonstrate that the drop in the activity fraction of M7 dwarfs can be explained by thin disk dynamical heating and a rapid decrease of magnetic activity at a mean stellar age of ~6-7 Gyr.

6 pages, accepted for publication in AJ

References in corpus (3)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Magnetic field generation in fully convective rotating spheres
• The large-scale axisymmetric magnetic topology of avery-low-mass fully-convective star

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• Common Proper Motion Companions to Nearby Stars: Ages and Evolution
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• A first eROSITA view of ultracool dwarfs
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