def get_pgeom(aor, e):
    """
    The geometric transit probability.

    See e.g. Kipping (2014) for the eccentricity factor
    http://arxiv.org/abs/1408.1393

    :param aor: the dimensionless semi-major axis (scaled
                by the stellar radius)
    :param e:   the orbital eccentricity

    """
    return 1. / (aor * (1 - e*e)) * (aor > 1.0)