  Context. The CoRoT short runs give us the opportunity to observe a large
variety of late-type stars through their solar-like oscillations. We report
observations of the star HD175726 that lasted for 27 days during the first
short run of the mission. The time series reveals a high-activity signal and
the power spectrum presents an excess due to solar-like oscillations with a low
signal-to-noise ratio. Aims. Our aim is to identify the most efficient tools to
extract as much information as possible from the power density spectrum.
Methods. The most productive method appears to be the autocorrelation of the
time series, calculated as the spectrum of the filtered spectrum. This method
is efficient, very rapid computationally, and will be useful for the analysis
of other targets, observed with CoRoT or with forthcoming missions such as
Kepler and Plato. Results. The mean large separation has been measured to be
97.2+-0.5 microHz, slightly below the expected value determined from solar
scaling laws.We also show strong evidence for variation of the large separation
with frequency. The bolometric mode amplitude is only 1.7+-0.25 ppm for radial
modes, which is 1.7 times less than expected. Due to the low signal-to-noise
ratio, mode identification is not possible for the available data set of
HD175726. Conclusions. This study shows the possibility of extracting a seismic
signal despite a signal-to-noise ratio of only 0.37. The observation of such a
target shows the efficiency of the CoRoT data, and the potential benefit of
longer observing runs.
