Bona-Masso slicing conditions and the lapse close to black-hole punctures

We consider several families of functions f (α ) that appear in the Bona-Masso slicing condition for the lapse function α . Focusing on spherically symmetric and time-independent slices we apply these conditions to the Schwarzschild spacetime in order to construct analytical expressions for the lapse α in terms of the areal radius R . We then transform to isotropic coordinates and determine the dependence of α on the isotropic radius r in the vicinity of the black-hole puncture. We propose generalizations of previously considered functions f (α ) for which, to leading order, the lapse is proportional to r rather than a noninteger power of r . We also perform dynamical simulations in spherical symmetry and demonstrate advantages of the above choices in numerical simulations employing spectral methods.