Period change investigation of the low mass ratio contact binary BO Ari

•The low mass ratio contact binary BO Ari with a fillout of 27.72% is presented.•The long-term orbital period decreases at a rate of dP/dt=−3.49×10−7dP/dt=−3.49×10−7 d yr−1−1.•BO Ari may evolve into a deeper contact system.

A photometric study and period change analysis for the A-type low mass ratio contact binary BO Ari is presented. The BVR light curves were fitted by using the Wilson–Devinney method. The photometric solution yields a low mass ratio of q = 0.1754(±0.0016) with a contact degree of f   = 27.72%(±2.37%). We found a long-term orbital period decrease at a rate of dPdt=−3.49×10−7dPdt=−3.49×10−7 d yr−1−1. This result indicates that the system is undergoing mass transfer from the primary component to the secondary with a mass transfer rate of m˙1m1 = −7.77×10−8−7.77×10−8 yr−1−1. With the period decrease, the inner and outer critical Roche surfaces will tighten and cause the degree of contact to increase. Therefore, BO Ari may evolve into a deeper contact system.