Wide-field searches for transiting extra-solar giant planets face the difficult challenge of separating true transit events from the numerous false positives caused by isolated or blended eclipsing binary systems .
We describe here the investigation of GSC 01944-02289 , a very promising candidate for a transiting brown dwarf detected by the Transatlantic Exoplanet Survey ( TrES ) network .
The photometry and radial velocity observations suggested that the candidate was an object of substellar mass in orbit around an F star .
However , careful analysis of the spectral line shapes revealed a pattern of variations consistent with the presence of another star whose motion produced the asymmetries observed in the spectral lines of the brightest star .
Detailed simulations of blend models composed of an eclipsing binary plus a third star diluting the eclipses were compared with the observed light curve and used to derive the properties of the three components .
Using the predicted stellar parameters we were able to identify a second set of spectral lines corresponding to the primary of the eclipsing binary and derive its spectroscopic orbit .
Our photometric and spectroscopic observations are fully consistent with a blend model of a hierarchical triple system composed of an eclipsing binary with G0V and M3V components in orbit around a slightly evolved F5 dwarf .
The rotational broadening of the spectral lines of the F5 primary ( v \sin i \approx 34 km s ^ { -1 } ) and its brightness relative to the eclipsing binary ( \sim 89 \% of the total light ) made the discovery of the true nature of the system particularly difficult .
We believe that this investigation will be helpful to other groups pursuing wide-field transit searches as this type of false detection could be more common than true transiting planets , and difficult to identify .