A new, low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

We present the discovery of a double-lined, detached eclipsing binary (EB), comprising two pre-main sequence M-dwarfs, in the 3 Myr old NGC 2264 star-forming region. Eclipses were detected in this system, during a continuous 23-day observation of NGC 2264 by the CoRoT space mission in 2008. Multi-epoch optical and near-IR follow-up spectroscopy with VLT/FLAMES and WHT/ISIS yielded a full orbital solution. We derive fundamental stellar parameters by modelling the light curve and radial velocity data, finding that the two stars travel on essentially circular orbits with a period of 3.8745745 ± 0.0000014 days and have masses of 0.67 ± 0.01 and 0.495 ± 0.007 M_sun with corresponding radii of 1.30 ± 0.04 and 1.11 ± 0.05 R_sun. The CoRoT light curve also contains large-amplitude, rapidly evolving out-of-eclipse variations, which are difficult to explain with star spots alone. SED modelling of the system's broadband optical and infrared magnitudes reveals a mid-IR excess, which we model as emission from a small amount of dust located within the inner cavity of a circumbinary disk. In turn, this opens up the possibility that some of the out-of-eclipse variability could be due to occultations of the central stars by material located at the inner edge or in the central cavity of the circumbinary disk.