2021MNRAS.502.5631Y

Galactic model plays an important role in the microlensing field, not only for analyses of individual events but also for statistics of the ensemble of events. However, the Galactic models used in the field vary, and some are unrealistically simplified. Here, we tested three Galactic disc dynamic models; the first is a simple standard model that was widely used in this field, the second model considers the radial dependence of the velocity dispersion, and the last model employs the asymmetric drift in the disc velocity distribution. We found that for a typical lens mass M_ L_=0.5 M_☉, the two new dynamical models predict ∼16 per cent or ∼5 per cent less long-time-scale events (e.g. microlensing time-scale t_E > 300 d) and ∼5 per cent and ∼3.5 per cent more short-time-scale events (t_E < 3 d) than the standard model. Moreover, the microlensing event rate as a function of Einstein radius θ_E or microlensing parallax π_E also shows some model dependence (a few per cent). The two new models also have an impact on the total microlensing event rate. This result will also to some degree affect the Bayesian analysis of individual events, but overall, the impact is small. However, we still recommend that modellers should be more careful when choosing the Galactic model, especially in statistical works involving Bayesian analyses of a large number of events. Additionally, we find the asymptotic power-law behaviours in both θ_E and π_E distributions, and we provide a simple model to understand them.