def FinalSpin( Xi, eta ):
    """Computes the spin of the final BH that gets formed after merger. This is done usingn Eq 5-6 of arXiv:0710.3345"""
    s4 = -0.129
    s5 = -0.384
    t0 = -2.686
    t2 = -3.454
    t3 = 2.353
    etaXi = eta * Xi
    eta2 = eta*eta
    finspin = (Xi + s4*Xi*etaXi + s5*etaXi*eta + t0*etaXi + 2.*(3.**0.5)*eta + t2*eta2 + t3*eta2*eta)
    if finspin > 1.0:
        raise ValueError("Value of final spin > 1.0. Aborting")
    else:
        return finspin
Computes the spin of the final BH that gets formed after merger. This is done usingn Eq 5-6 of arXiv:0710.3345