DEFINITION AND PROPERTIES OF QUASIBLACK HOLES

We consider the quasiblack hole limit of a stationary body when its boundary approaches its own gravitational radius, i.e., its quasihorizon. There exists a perfect correspondence between the mass formulas for quasiblack and black holes in spite of difference in derivation and meaning of the formulas. For extremal quasiblack holes the finite surface stresses give zero contribution to the mass. Analogous properties hold for the angular momentum.