Let \( S \) be the focus of the hyperbola \( \dfrac{x^{2}}{3}-\dfrac{y^{2}}{5}=1 \), on the positive \( x \)-axis. Let \( C \) be the circle with its centre at \( A(\sqrt{6},\sqrt{5}) \) and passing through the point \( S \). If \( O \) is the origin and \( SAB \) is a diameter of \( C \), then the square of the area of the triangle \( OSB \) is equal to ________.
