  We estimate the Coulomb energy of static quarks from a Monte Carlo
calculation of the correlator of timelike link variables in Coulomb gauge. We
find, in agreement with Cucchieri and Zwanziger, that this energy grows
linearly with distance at large quark separations. The corresponding string
tension, however, is several times greater than the accepted asymptotic string
tension, indicating that a state containing only static sources, with no
constituent gluons, is not the lowest energy flux tube state. The Coulomb
energy is also measured on thermalized lattices with center vortices removed by
the de Forcrand-D'Elia procedure. We find that when vortices are removed, the
Coulomb string tension vanishes.
