THE ROTATION AND GALACTIC KINEMATICS OF MID M DWARFS IN THE SOLAR NEIGHBORHOOD

2015/11/30 by Elisabeth R. Newton, Jonathan Irwin, David Charbonneau +3 · 275 citations
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Astronomy and Astrophysical Research #Dynamo #Geomagnetism and Paleomagnetism Studies #Metallicity #Photometry (optics) #Population #Rotation (mathematics) #Rotation period #Stars #Stellar rotation #Stellar, planetary, and galactic studies #astro-ph.GA #astro-ph.SR

paper · pdf · doi:10.3847/0004-637x/821/2/93

published in The Astrophysical Journal 821(2), 93 (IOP Publishing) · Accepted to ApJ. Machine readable tables and additional figures are available in the published article or on request

arxiv created 2016/02/18 · openalex publication_date 2016/04/14 · arxiv updated 2016/04/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06

Abstract

ABSTRACT Rotation is a directly observable stellar property, and it drives magnetic field generation and activity through a magnetic dynamo. Main-sequence stars with masses below approximately 0.35 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> (mid-to-late M dwarfs) are fully convective, and are expected to have a different type of dynamo mechanism than solar-type stars. Measurements of their rotation rates provide insight into these mechanisms, but few rotation periods are available for these stars at field ages. Using photometry from the MEarth Project, we measure rotation periods for 387 nearby, mid-to-late M dwarfs in the northern hemisphere, finding periods from 0.1 to 140 days. The typical rotator has stable, sinusoidal photometric modulations at a semi-amplitude of 0.5%–1%. We find no period–amplitude relation for stars below 0.25 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> and an anticorrelation between period and amplitude for higher-mass M dwarfs. We highlight the existence of older, slowly rotating stars without H α emission that nevertheless have strong photometric variability. We use parallaxes, proper motions, radial velocities, photometry, and near-infrared metallicity estimates to further characterize the population of rotators. The Galactic kinematics of our sample is consistent with the local population of G and K dwarfs, and rotators have metallicities characteristic of the solar neighborhood. We use the W space velocities and established age–velocity relations to estimate that stars with P &lt; 10 days have ages of on average &lt;2 Gyr, and that those with P &gt; 70 days have ages of about 5 Gyr. The period distribution is dependent on mass: as the mass decreases, the slowest rotators at a given mass have longer periods, and the fastest rotators have shorter periods. We find a lack of stars with intermediate rotation periods, and the gap between the fast and slow rotators is larger for lower masses. Our data are consistent with a scenario in which these stars maintain rapid rotation for several gigayears, then spin down quickly, reaching periods of around 100 days by a typical age of 5 Gyr.

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• The CARMENES search for exoplanets around M dwarfs
• A Catalog of M-dwarf Flares with ASAS-SN