  We analyze the magnetic field and gate voltage dependence of the longitudinal
resistance in an integer quantum Hall Fabry-P\'{e}rot interferometer, taking
into account the interactions between an interfering edge mode, a
non-interfering edge mode and the bulk. For weak bulk-edge coupling and
sufficiently strong inter-edge interaction, we obtain that the interferometer
operates in the Aharonov-Bohm regime with a flux periodicity halved with
respect to the usual expectation. Even in the regime of strong bulk-edge
coupling, this behavior can be observed as a subperiodicity of the interference
signal in the Coulomb dominated regime. We do not find evidence for a
connection between a reduced flux period and electron pairing, though. Our
results can reproduce some recent experimental findings.
