  We present precise measurements of the assembly bias of dark matter halos,
i.e. the dependence of halo bias on other properties than the mass, using
curved "separate universe" N-body simulations which effectively incorporate an
infinite-wavelength matter overdensity into the background density. This method
measures the LIMD (local-in-matter-density) bias parameters $b_n$ in the
large-scale limit. We focus on the dependence of the first two Eulerian biases
$b^E_1$ and $b^E_2$ on four halo properties: the concentration, spin, mass
accretion rate, and ellipticity. We quantitatively compare our results with
previous works in which assembly bias was measured on fairly small scales.
Despite this difference, our findings are in good agreement with previous
results. We also look at the joint dependence of bias on two halo properties in
addition to the mass. Finally, using the excursion set peaks model, we attempt
to shed new insights on how assembly bias arises in this analytical model.
