def metalicity_jk_v_band(period, phi31_v):
    """
    Returns the JK96 caclulated metalicity of the given RRab RR Lyrae.

    (Jurcsik and Kovacs, 1996) (3)
    (Szczygiel et al., 2009) (6)
    (Skowron et al., 2016) (1)

    Parameters
    ----------
    period : float64
        The period of the star.
    phi31_v : float64
        The V band phi31 of the star.

    Returns
    -------
    metalicity_jk_v : float64
        The JK96 metalicity of the star.
    """
    return -5.038 - 5.394 * period + 1.345 * phi31_v