Isometric immersions into Lorentzian products

We give a necessary and sufficient condition for an n-dimensional Riemannian manifold to be isometrically immersed into one of the Lorentzian products Sn×R1 or Hn×R1. This condition is expressed in terms of its first and second fundamental forms, the tangent and normal projections of the vectical vector field. As applications, we give an equivalent condition in a spinorial way and we deduce the existence of a one-parameter family of isometric maximal deformation of a given maximal surface obtained by rotating the shape operator.