CONSTRAINING THE AGE–ACTIVITY RELATION FOR COOL STARS: THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 5 LOW-MASS STAR SPECTROSCOPIC SAMPLE

By Andrew A. West, S. Hawley, J. Bochanski, K. Covey, I. Neill Reid, S. Dhital, E. Hilton, M. Masuda. 2007

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We present a spectroscopic analysis of over 38,000 low-mass stars from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Analysis of this unprecedentedly large sample confirms the previously detected decrease in the fraction of magnetically active stars (as traced by Hα emission) as a function of the vertical distance from the Galactic plane. The magnitude and slope of this effect vary as a function of spectral type. Using simple 1D dynamical models, we demonstrate that the drop in activity fraction can be explained by thin-disk dynamical heating and a rapid decrease in magnetic activity. The timescale for this rapid activity decrease changes according to the spectral type. By comparing our data to the simulations, we calibrate the age–activity relation at each M dwarf spectral type. We also present evidence for a possible decrease in the metallicity as a function of height above the Galactic plane. In addition to our activity analysis, we provide line measurements, molecular band indices, colors, radial velocities, 3D space motions, and mean properties as a function of spectral type for the SDSS DR5 low-mass star sample.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/516693836105c4ac4e754235abc4e492020cff86

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Citations in the corpus

THE SPITZER DEEP, WIDE-FIELD SURVEY (2009, methodology): “On the basis of its SDSS spectrum, West et al. (2008) assign this object a spectral type of M5—again consistent with the type inferred on the basis of the IRAC color.”
BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, methodology): “We note that our field sequences are slightly redder than those derived from samples based on the Sloan Digital Sky Survey (SDSS; York et al. 2000) such as those presented by West et al. (2008) and Schmidt et al. (2015).”
Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs (2019, result): “Given that young M dwarfs were more active (West et al. 2008) and thus assuming that their flaring was more frequent and energetic in the past, our results provide a lower limit.”
Exoplanet Atmospheres: Physical Processes (2010, background): “Flares and UV radiation could erode planet atmospheres (Lammer et al. 2007), especially because the active phase of M stars can last for billions of years (West et al. 2008).”
Individual Dynamical Masses of Ultracool Dwarfs (2017, background): “51−001304.1AB is much more distant (160 ± 30 pc) and thus wider (9.0 ± 1.7 AU) than previously estimated given that its spectral type is M7 (West et al. 2008) not early- to mid-L.”
THE SOLAR NEIGHBORHOOD. XXXVII. THE MASS–LUMINOSITY RELATION FOR MAIN-SEQUENCE M DWARFS (2016, background): “Late-type stars like GJ 1245AC can remain active on a timescale of ∼8 Gyr (see West et al. 2008), so it is perhaps not surprising that the stars might be quite old but still active.”
FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, unknown): “…et al. (2015, in preparation), (36) Burgasser et al. (2002a), (37) Luyten (1979b), (38) Kirkpatrick et al. (1997), (39) Metchev et al. (2008), (40) West et al. (2008), (41) Turnbull & Tarter (2003), (42) Henry et al. (2006), (43) Luhman et al. (2009), (44) Scholz et al. (2011), (45) Kirkpatrick…”
THE MILKY WAY TOMOGRAPHY WITH SDSS. III. STELLAR KINEMATICS (2009, methodology): “Such an age gradient, together with the measured velocity dispersion–age correlations for local disk stars (e.g., Nordström et al. 2004; Rocha-Pinto et al. 2004; West et al. 2008), may be responsible for the measured increase of velocity dispersions with distance from the Galactic plane.”
Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life (2017, background): “However, our planet was inhabited for very long periods before the evolution of land plants at *0.5 Gyr (and the evolution of cyanobacteria 3.0 Gyr and the subsequent rise of O2 at *2.4 Gyr).”
THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, background): “The active periods of M stars are more prolonged than the equivalent “youthful magnetic exuberance” (Ayres & France 2010) period of solar-type stars (e.g., West et al. 2008).”
Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs (2008, background): “An age-activity relation has recently been quantified by West et al. (2008), which could be related to rotational braking and a rotationactivity connection.”
BANYAN. II. VERY LOW MASS AND SUBSTELLAR CANDIDATE MEMBERS TO NEARBY, YOUNG KINEMATIC GROUPS WITH PREVIOUSLY KNOWN SIGNS OF YOUTH (2013, methodology): “Faherty et al. (2012) measure its distance to be 38± 16 pc, and we combine the radial velocity measurements of Schmidt et al. (2010) and West et al. (2008) into −7.9± 4.8 km s−1.”
A NEARBY M STAR WITH THREE TRANSITING SUPER-EARTHS DISCOVERED BY K2 (2015, background): “The strongest line in the series, Hα at 6563 Å, is classically used to asses the activity of M dwarfs and as a crude indicator of age (West et al. 2004, 2008).”
ON THE ANGULAR MOMENTUM EVOLUTION OF FULLY CONVECTIVE STARS: ROTATION PERIODS FOR FIELD M-DWARFS FROM THE MEarth TRANSIT SURVEY (2010, methodology): “3 of West et al. 2008).”
LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) — The survey's science plan (2012, background): “…patterns which now make it possible to evaluate metallicities (Lepine et al. 2007; Woolfe, Lepine, & Wallerstein 2009; Rojas-Ayala et al. 2012) and identify relatively young (< 500Myr) M dwarfs (West et al. 2008; Schlieder et al. 2012) based on spectral features in the red-optical and near-IR.”
RADIUS-DEPENDENT ANGULAR MOMENTUM EVOLUTION IN LOW-MASS STARS. I (2011, methodology): “Activity lifetimes of M dwarfs were determined by West et al. (2008), who define “lifetime” as the typical timescale over which Hα can be observed in emission in their sample, before the emission falls below their detection limit.”
Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life (2014, background): “The 13% active fraction and the trend with spectral type are consistent with previous studies of M dwarf activity (e.g., West et al. 2008; Gizis et al. 2000), which find typical active fractions for early-M dwarfs (M0-M3) to be ∼10%.”
PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, background): “These targets appear to be old inactive field stars that passed early NUV selection cuts, so we adopt minimum ages from the activity-lifetime relations of West et al. (2008).”
AN ALL-SKY CATALOG OF BRIGHT M DWARFS (2011, result): “In contrast to late-type M stars, the vast majority of early M dwarfs are not rapid rotators or chromospherically active (WHα > 1Å) (Bochanski et al. 2005; West et al. 2008; Reiners & Basri 2008) and are thus amenable to these search techniques.”