▎ 摘　　要

We study low-energy massless electronic excitations in a graphene monolayer near a pointlike Coulomb impurity. We assume that such excitations are described by the Dirac model. We construct a family of self-adjoint Hamiltonians corresponding to these excitations for any charge of the impurity and perform their spectral analysis. It is shown that in this case, the structure of electron excitation spectra differs qualitatively from the corresponding spectra of massive excitations. The obtained results are used for analyzing the local surface density of electron states in graphene and its dependence of the choice of self-adjoint Hamiltonians.