  We analyze heat and work fluctuations in the gravitational wave detector
AURIGA, modeled as a macroscopic electromechanical oscillator in contact with a
thermostat and cooled by an active feedback system. The oscillator is driven to
a steady state by the feedback cooling, equivalent to a viscous force. The
experimentally measured fluctuations are in agreement with our theoretical
analysis based on a stochastically driven Langevin system. The asymmetry of the
fluctuations of the absorbed heat characterizes the oscillator's nonequilibrium
steady state and reveals the extent to which a feedback cooled system departs
from equilibrium in a statistical mechanics perspective.
