  We examine theoretically the signatures of magnetic adatoms in graphene
probed by scanning tunneling spectroscopy (STS). When the adatom hybridizes
equally with the two graphene sublattices, the broadening of the local adatom
level is anomalous and can scale with the cube of the energy. In contrast to
ordinary metal surfaces, the adatom local moment can be suppressed by the
proximity of the probing scanning tip. We propose that the dependence of the
tunneling conductance on the distance between the tip and the adatom can
provide a clear signature for the presence of local magnetic moments. We also
show that tunneling conductance can distinguish whether the adatom is located
on top of a carbon atom or in the center of a honeycomb hexagon.
