Sine & Cosine

Geometry Level 2

If $\sqrt{3}\cos \theta-\sin \theta=\frac{1}{3}$ and $0 < \theta < \frac{\pi}{2},$ the value of $\sqrt{3}\sin \theta+\cos \theta$ can be expressed as $\frac{\sqrt{a}}{3}$ . What is the value of $a?$