We present the results of our study of the eclipsing binary systems CSS J112237.1+395219 , LINEAR 1286561 and LINEAR 2602707 based on new CCD B , V , R _ { c } and I _ { c } complete light curves .
The ultra-short period nature of the stars ( Drake et al . 2014 ) is confirmed and the system ’ s periods are revised .
The light curves were modelled using the 2005 version of the Wilson-Devinney code .
When necessary , cool spots on the surface of the primary component were introduced to account for asymmetries in the light curves .
As a result , we found that CSS J112237.1+395219 is a W UMa type contact binary system belonging to W subclass with a mass ratio of q = 1.61 and a shallow degree of contact of 14.8 % where the primary component is hotter than the secondary one by 500 K .
LINEAR 1286561 and LINEAR 2602707 are detached binary systems with mass ratios q = 3.467 and q = 0.987 respectively .
These detached systems are low-mass M-type eclipsing binaries of similar temperatures .
The marginal contact , the fill-out factor and the temperature difference between components of CSS J112237.1+395219 suggest that this system may be at a key evolutionary state predicted by the Thermal Relaxation Oscillation theory ( TRO ) .
From the estimated absolute parameters we conclude that our systems share common properties with others ultra-short period binaries .