  We analyze the fluctuations of an electronic thermal current across an
idealized molecular junction. The focus here will be on the spectral features
of the resulting heat fluctuations. By use of the Green functionmethod we
derive an explicit expression for the frequency-dependent power spectral
density of the emerging energy fluctuations. The complex expression simplifies
considerably in the limit of zero frequency, yielding the noise intensity of
the heat current. The spectral density for the electronic heat fluctuations
still depends on the frequency in the zero-temperature limit, assuming
different asymptotic behaviours in the low- and high-frequency regions. We
further address subtleties and open problems from an experimental viewpoint for
measurements of frequency-dependent power spectral densities.
