Low mass stars (less massive then the Sun) of spectral type K and M are the most abundant stars in our Galaxy. Nevertheless due to their small brightness they are relatively poorly investigated. Very few such stars are known in the eclipsing detached binary systems. In such systems we can estimate directly principal stellar parameters such as mass, radius and temperature. Our models of stellar structure usually predict smaller sizes and higher temperatures then observed. This is why each new eclipsing binary system of low mass stars is a valuable finding for theoreticians.
A newly discovered and described system ASAS J011328-3821.1 A (in brief ASAS-011) is unique even in this group of rare objects. Eclipsing binary with orbital period of 0.45 day contains stars with masses of 0.61 and 0.45 solar masses. In addition, in the proximity of eclipsing binary A there is visible much fainter component B. It is possible to estimate some parameters of this component as well. There is some evidence the component B is a binary system too. It contains two stars with masses close to 0.5 solar masses. Until now only two objects of similar configurations were known.
ASAS-011 was discovered by K. G. Hełminiak, M. Konacki, M. Rozyczka, J. Kaluzny, M. Ratajczak, J. Borkowski, P. Sybilski from the Copernicus Center and their collaborators from Chile and the US.
