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 > 20 Myr , 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 ) .