its axis, a rough estimate of the associated magnetic moment ${\boldsymbol{M}}_S$ can be obtained by treating such an object as composed by classical particles in uniform rotation with a given angular frequency $\om$, and by associating to such particles the magnetic moment obtained from .

More in detail, we choose a reference system in which the orbit lies on the $(x,y)$ plane, and we indicate by $(\theta,\phi)$ the spherical coordinates of ${\boldsymbol{e}}$ with respect to this system. Moreover, recalling that for the binary black hole giving rise to the event GW150914 the angular frequency just before the merger was $\omega \cong 471 \,s^{-1}$ and the radius of the orbit was $R \cong 350 \,km$ [@LV], so that the speed in natural units ($\hbar = c = 1$) was $\beta = \om R \cong 0.6$, we may also assume that the motion of the particles is non-relativistic and approximate $\omega({{\boldsymbol{k}}}) \cong m$ in . We obtain then $$\label{eq:starmoment}\begin{split}
{\boldsymbol{M}}_S(t) = e\la_P^2M&\left\{2R\om 
\left(\begin{matrix}
\cos \om t \cos \theta\\
\sin \om t \cos \theta\\
-\cos (\om t-\phi) \sin \theta
\end{matrix}\right)
\right.\\
&\left.+ R^2\om^2\left[
\left(\begin{matrix}
\sin\theta(\cos\phi-\sin \omega t \sin(\omega t-\phi)) \\
\sin \theta(\sin \phi + \cos \omega t \sin(\omega t-\phi))\\
\cos \theta
\end{matrix}\right)
+\frac 