  We investigate conserved charges in the low-energy effective field theory
describing heterotic string theory. Starting with a general Lagrangian that
consists of a metric, a scalar field, a vector gauge field, together with a
two-form potential, we derive off-shell Noether potentials of the Lagrangian
and generalize the Abbott-Deser-Tekin (ADT) formalism to the off-shell level by
establishing one-to-one correspondence between the ADT potential and the
off-shell Noether potential. It is proved that the off-shell generalized ADT
formalism is conformally invariant. Then we apply the formulation to compute
mass and angular momentum of the four-dimensional Kerr-Sen black hole and the
five-dimensional rotating charged black string in the string frame without a
necessity to transform the metrics into the Einstein frame.
