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 HD 175726 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 \pm 0.5 \mu Hz , 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 \pm 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 HD 175726 .

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 .