  We investigate the gravitational waves phenomena in the geometric scalar
theory of gravity (GSG) that belongs to a class of theories such that gravity
is described by a single scalar field. The associated physical metric
describing the spacetime is constructed from a disformal transformation of
Minkowski geometry. In this theory, a weak field approximation gives rise to a
description similar to that one obtained in general relativity, although the
gravitational waves in GSG have a characteristic longitudinal polarization
mode, besides others modes that are observer dependent. We also analyze the
energy carried by the gravitational waves as well as how their emission affects
the orbital period of a binary system.
