Using magnetic activity and Galactic dynamics to constrain the ages of M dwarfs

West, Andrew A.; Hawley, Suzanne L.; Bochanski, John J.; Covey, Kevin R.; Burgasser, Adam J.

doi:10.1017/s1743921309031986

Cited by 5 publications

(7 citation statements)

References 41 publications

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“…Delfosse et al 1998;Mohanty & Basri 2003;Reiners et al 2012;West et al 2015;Newton et al 2017). Furthermore, several studies have extended the idea that magnetic activity decreases with age for late-M dwarfs (Fleming et al 1995;Eggen 1990;West et al 2006West et al , 2008aRiedel et al 2017). This indicates that there is an empirical relation between age, rotation and magnetic activity for M dwarfs that may extend to L dwarfs as well.…”

Section: Introductionmentioning

confidence: 90%

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Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

et al. 2019

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We present a sample of 74, 216 M and L dwarfs a) constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for late-M and L dwarfs. We also provide relations between Gaia colors and absolute magnitudes with spectral type and conclude that (G − G RP ) has the tightest relation to spectral type for M and L dwarfs. In addition, we study magnetic activity as a function of position on the color-magnitude diagram, finding that Hα magnetically active stars have, on average, redder colors and/or brighter magnitudes than inactive stars. This effect cannot be explained by youth alone and might indicate that active stars are magnetically inflated, binaries and/or high metallicity. Moreover, we find that vertical velocity and vertical action dispersion are correlated with Hα emission, confirming that these two parameters are age indicators. We also find that stars below the main sequence have high tangential velocity which is consistent with a low metallicity and old population of stars that belong to the halo or thick disk.

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Section: Introductionmentioning

confidence: 90%

“…This relationship is particularly strong when examining the correlations between Galactic height or vertical velocity and age (e.g. West et al 2006West et al , 2008aNordstrom et al 2004;Aumer et al 2016;Yu & Liu 2018). This statistical method was used by several works to obtain kinematic ages of population of stars (e.g.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

et al. 2019

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“…We discuss active cool dwarfs and flaring giants together. M dwarfs are known to have active chromospheres, although old ones get less active (West et al 2008). In addition, Schiavon et al (2005) observed a probable bright, red giant flaring in their spectra.…”

Section: Emission Fill Inmentioning

confidence: 99%

On the Anomalous Balmer Line Strengths in Globular Clusters

Poole

Worthey

Serven

2010

The Astronomical Journal

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Spectral feature index diagrams with integrated globular clusters and simple stellar population models often show that some clusters have weak Hβ, so weak that even the oldest models cannot match the observed feature depths. In this work, we rule out the possibility that abundance mixture effects are responsible for the weak indices unless such changes operate to cool the entire isochrone. We discuss this result in the context of other explanations, including horizontal branch morphology, blue straggler populations, and nebular or stellar emission fill-in, finding a preference for flaring in M giants as an explanation for the Hβ anomaly.

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“…For young M stars with Hα emission lines (so-called active M dwarfs), stellar activity has been shown to be tightly coupled with rotation (e.g., Browning et al 2010;Reiners et al 2012). Furthermore, as these stars age and spin down, their Hα emission and variability decrease significantly, offering a diagnostic for distinguishing stellar populations of different ages (West et al 2008(West et al , 2009López-Santiago et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Hα ACTIVITY OF OLD M DWARFS: STELLAR CYCLES AND MEAN ACTIVITY LEVELS FOR 93 LOW-MASS STARS IN THE SOLAR NEIGHBORHOOD

Robertson

Endl

Cochran

et al. 2013

ApJ

110

120

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Through the McDonald Observatory M Dwarf Planet Search, we have acquired nearly 3000 high-resolution spectra of 93 late-type (K5-M5) stars over more than a decade using the High Resolution Spectrograph on the Hobby-Eberly Telescope. This sample provides a unique opportunity to investigate the occurrence of long-term stellar activity cycles for low-mass stars. In this paper, we examine the stellar activity of our targets as reflected in the Hα feature. We have identified periodic signals for six stars, with periods ranging from days to more than 10 years, and find long-term trends for seven others. Stellar cycles with P 1 year are present for at least 5% of our targets. Additionally, we present an analysis of the time-averaged activity levels of our sample, and search for correlations with other stellar properties. In particular, we find that more massive, earlier type (M0-M2) stars tend to be more active than later type dwarfs. Furthermore, high-metallicity stars tend to be more active at a given stellar mass. We also evaluate Hα variability as a tracer of activity-induced radial velocity (RV) variation. For the M dwarf GJ 1170, Hα variation reveals stellar activity patterns matching those seen in the RVs, mimicking the signal of a giant planet, and we find evidence that the previously identified stellar activity cycle of GJ 581 may be responsible for the recently retracted planet f in that system. In general, though, we find that Hα is not frequently correlated with RV at the precision (typically 6-7 m s −1 ) of our measurements.

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Using magnetic activity and Galactic dynamics to constrain the ages of M dwarfs

Cited by 5 publications

References 41 publications

Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

On the Anomalous Balmer Line Strengths in Globular Clusters

Hα ACTIVITY OF OLD M DWARFS: STELLAR CYCLES AND MEAN ACTIVITY LEVELS FOR 93 LOW-MASS STARS IN THE SOLAR NEIGHBORHOOD

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