Photometric observations in the R and I bands of the detached M-type double-lined eclipsing binary CU Cnc have been acquired and analysed .
The photometric elements obtained from the analysis of the light curves have been combined with an existing spectroscopic solution to yield high-precision ( errors \la 2 % ) absolute dimensions : M _ { A } = 0.4333 \pm 0.0017 M _ { \sun } , M _ { B } = 0.3980 \pm 0.0014 M _ { \sun } , R _ { A } = 0.4317 \pm 0.0052 R _ { \sun } , and R _ { B } = 0.3908 \pm 0.0094 R _ { \sun } .
The mean effective temperature of the system has been estimated to be T _ { eff } = 3140 \pm 150 K by comparing multi-band photometry ( optical and infrared ) with synthetic colors computed from state-of-the-art model atmospheres .
Additionally , we have been able to obtain an estimate for the age ( \sim 320 Myr ) and chemical composition ( [ \mbox { Fe / H } ] \approx 0.0 ) of the binary system through its membership of the Castor moving group .
With all these observational constraints , we have carried out a critical test of recent stellar models for low-mass stars .
The comparison reveals that most evolutionary models underestimate the radius of the stars by as much as 10 % , thus confirming the trend observed by Torres & Ribas ( [ 2002 ] ) for YY Gem and V818 Tau .
In the mass–absolute magnitude diagram , CU Cnc is observed to be dimmer than other stars of the same mass and this makes the comparison with stellar models not so compelling .
After ruling out a number of different scenarios , the apparent faintness of CU Cnc can be explained if its components are some 10 % cooler than similar-mass stars or if there is some source of circumstellar dust absorption .
The latter could be a tantalizing indirect evidence for a coplanar ( Vega-like ) dusty disk around this relatively young M-type binary .