#### Answer

$x^{2}$ + $y^{2}$ = 3

#### Work Step by Step

The equation $(x-h)^{2}$ + $(y-k)^{2}$ = $r^{2}$ is an equation that describes a circle. In this problem, $(h, k)$, the center, is $(0,0)$, and $r$, the radius, is $\sqrt 3$. Therefore, the equation of this circle is $x^{2}$ + $y^{2}$ = 3.