Context :

Aims : The recently discovered eclipsing binary system TYC 2675-663-1 is a X-ray source , and shows properties in the optical that are similar to the W UMa systems , but are somewhat unusual compared to what is seen in other contact binary systems .
The goal of this work is to characterize its properties and investigate its nature by means of detailed photometric and spectroscopic observations .

Methods : We have performed extensive V -band photometric measurements with the INTEGRAL satellite along with ground-based multi-band photometric observations , as well as high-resolution spectroscopic monitoring from which we have measured the radial velocities of the components .
These data have been analysed to determine the stellar properties , including the absolute masses and radii .
Additional low-resolution spectroscopy was obtained to investigate spectral features .

Results : From the measured eclipse timings we determine an orbital period for the binary of P = 0.4223576 \pm 0.0000009 days .
The light-curve and spectroscopic analyses reveal the observations to be well represented by a model of an overcontact system composed of main-sequence F5 and G7 stars ( temperature difference of nearly 1000 K ) , with the possible presence of a third star .
Low-resolution optical spectroscopy reveals a complex H _ { \alpha } emission , and other features that are not yet understood .
The unusually large mass ratio of q = 0.81 \pm 0.05 places it in the rare “ H ” ( high mass ratio ) subclass of the W UMa systems , which are presumably on their way to coalescence .

Conclusions :