CoRoT 223992193: A new, low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

• Published in: Astronomy and astrophysics (Berlin) 2014-02, Vol.562, p.np-np
• Main Authors: Gillen, E., Aigrain, S., McQuillan, A., Bouvier, J., Hodgkin, S., Alencar, S. H. P., Terquem, C., Southworth, J., Gibson, N. P., Cody, A., Lendl, M., Morales-Calderón, M., Favata, F., Stauffer, J., Micela, G.
• Format: Article
• Language: English
• Subjects: Astrophysics; binaries: eclipsing; binaries: spectroscopic; Clusters; Disks; Eclipsing binary stars; Evolutionary; Holes; Light curve; Mathematical models; open clusters and associations: individual: NGC 2264; protoplanetary disks; Sciences of the Universe; Spectral energy distribution; stars: individual: CoRoT 223992193; stars: pre-main sequence
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361/201322493

We present the discovery of CoRoT 223992193, a double-lined, detached eclipsing binary, comprising two pre-main sequence M dwarfs, discovered by the CoRoT space mission during a 23-day observation of the 3 Myr old NGC 2264 star-forming region. Using multi-epoch optical and near-IR follow-up spectroscopy with FLAMES on the Very Large Telescope and ISIS on the William Herschel Telescope we obtain a full orbital solution and derive the fundamental parameters of both stars by modelling the light curve and radial velocity data. The orbit is circular and has a period of 3.8745745 ± 0.0000014 days. The masses and radii of the two stars are 0.67 ± 0.01 and 0.495 ± 0.007 M⊙ and 1.30 ± 0.04 and 1.11-0.05+0.04 R⊙, respectively. This system is a useful test of evolutionary models of young low-mass stars, as it lies in a region of parameter space where observational constraints are scarce; comparison with these models indicates an apparent age of ~3.5–6 Myr. The systemic velocity is within 1σ of the cluster value which, along with the presence of lithium absorption, strongly indicates cluster membership. The CoRoT light curve also contains large-amplitude, rapidly evolving out-of-eclipse variations, which are difficult to explain using starspots alone. The system’s spectral energy distribution reveals a mid-infrared excess, which we model as thermal emission from a small amount of dust located in 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.