We exploit the [ Mg/Mn ] - [ Al/Fe ] chemical abundance plane to help identify nearby halo stars in the 14th data release from the APOGEE survey that have been accreted on to the Milky Way .
Applying a Gaussian Mixture Model , we find a ‘ blob ’ of 856 likely accreted stars , with a low disc contamination rate of \sim 7 % .
Cross-matching the sample with the second data release from Gaia gives us access to parallaxes and apparent magnitudes , which place constraints on distances and intrinsic luminosities .
Using a Bayesian isochrone pipeline , this enables us to estimate new ages for the accreted stars , with typical uncertainties of \sim 20 % .
Our new catalogue is further supplemented with estimates of orbital parameters .

The blob stars span a metallicities between -0.5 to -2.5 , and [ Mg/Fe ] between -0.1 to 0.5 .
They constitute \sim 30 % of the metal-poor ( [ Fe/H ] < -0.8 ) halo at metallicities of \sim -1.4 .
Our new ages are mainly range between 8 to 13 Gyr , with the oldest stars the metal-poorest , and with the highest [ Mg/Fe ] abundance .
If the blob stars are assumed to belong to a single progenitor , the ages imply that the system merged with our Milky Way around 8 Gyr ago and that star formation proceeded for 5 Gyr .
Dynamical arguments suggest that such a single progenitor would have a total mass of \sim 10 ^ { 11 } M _ { \odot } , similar to that found by other authors using chemical evolution models and simulations .
Comparing the scatter in the [ Mg/Fe ] - [ Fe/H ] plane of the blob stars to that measured for stars belonging to the Large Magellanic Cloud suggests that the blob does indeed contain stars from only one progenitor .