On the age of the β Pictoris moving group

By Eric Mamajek, C. Bell. 2014

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Jeffries & Binks (2014) and Malo et al. (2014) have recently reported Li depletion boundary (LDB) ages for the {\beta} Pictoris moving group (BPMG) which are twice as old as the oft-cited kinematic age of $\sim$12 Myr. In this study we present (1) a new evaluation of the internal kinematics of the BPMG using the revised Hipparcos astrometry and best available published radial velocities, and assess whether a useful kinematic age can be derived, and (2) derive an isochronal age based on the placement of the A-, F- and G-type stars in the colour-magnitude diagram (CMD). We explore the kinematics of the BPMG looking at velocity trends along Galactic axes, and conducting traceback analyses assuming linear trajectories, epicyclic orbit approximation, and orbit integration using a realistic gravitational potential. None of the methodologies yield a kinematic age with small uncertainties using modern velocity data. Expansion in the Galactic X and Y directions is significant only at the 1.7{\sigma} and 2.7{\sigma} levels, and together yields an overall kinematic age with a wide range (13-58 Myr; 95 per cent CL). The A-type members are all on the zero age-main-sequence, suggestive of an age of $>$20Myr, and the loci of the CMD positions for the late-F- and G-type pre-main-sequence BPMG members have a median isochronal age of 22 Myr ($\pm$ 3 Myr stat., $\pm$ 1 Myr sys.) when considering four sets of modern theoretical isochrones. The results from recent LDB and isochronal age analyses are now in agreement with a median BPMG age of 23 $\pm$ 3 Myr (overall 1{\sigma} uncertainty, including $\pm$2 Myr statistical and $\pm$2 Myr systematic uncertainties).

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/910e8c90a37c9eef49bb2cf79d8c7eab00b3ca2d

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Citations in the corpus

The star formation history and accretion-disc fraction among the K-type members of the Scorpius–Centaurus OB association (2016, methodology): “The Mamajek & Bell (2014) study found the modern BPMG kinematic data was only weakly indicitave of expansion, and that the age is only weakly constrained by the kinematic data, giving a 95 confidence limit of 13-58 Myr.”
Imaging Extrasolar Giant Planets (2016, background): “The implied hot-start mass for β Pic b, for example, increases by several Jupiter masses (corresponding to several tens of percent) assuming the planet’s age is ≈23 Myr instead of ≈12 Myr (Mamajek & Bell 2014; although see the next bullet point).”
A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood (2015, methodology): “Furthermore, these kinematic methods have also been shown to be unreproducible when similar analyses have been performed using improved astrometric data (e.g. Murphy, Lawson, & Bessell 2013; Mamajek & Bell 2014).”
PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, result): “…(2005), (4) Torres et al. (2006), (5) Weinberger et al. (2013), (6) Yee & Jensen (2010), (7) Binks & Jeffries (2014), (8) Malo et al. (2014b), (9) Mamajek & Bell (2014), (10) Torres et al. (2008), (11) Torres et al. (2000) (12) Zuckerman et al. (2001), (13) Kraus et al. (2014), (14) Torres et…”
BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, background): “It is also possible that the current age estimate of THA is wrong– e.g., βPMG, Upper Scorpius, AB Doradus and the Pleiades have recently been found to be slightly older than previously thought (Luhman et al. 2005; Pecaut et al. 2012; Malo et al. 2014b; Binks & Jeffries 2014; Mamajek & Bell 2014).”
THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, background): “We note that the Mamajek & Bell (2014) group membership suggests that β Pic membership is still a marginal option, with χ̃2UVW=3.2, χ̃ 2 XY Z=1.2, and a velocity distance of 5.2 km s −1.”