We improve upon the simple model studied by Casadio and Orlandi [JHEP 1308
(2013) 025] for a black hole as a condensate of gravitons. Instead of the
harmonic oscillator potential, the P\"oschl-Teller potential is used, which
allows for a continuum of scattering states. The quantum mechanical model is
embedded into a relativistic wave equation for a complex Klein-Gordon field,
and the charge of the field is interpreted as the gravitational charge (mass)
carried by the graviton condensate.Comment: 12 pages, 1 figure, v2: typos correcte