def ptilde(d, dstar):
    """Unnormalized probability density.

    ptilde(d) = d^2 / (2 d / (3 dstar) + 1)^5

    Arguments:
        d {float} -- luminosity distance
        dstar {float} -- peak distance

    Returns:
        float -- unnormalized probability
    """
    return d**2 / (2*d/(3*dstar) + 1)**5