def retr_radiroch(radistar, densstar, denscomp):
    """
    Return the Roche limit

    Arguments
        radistar: radius of the primary star
        densstar: density of the primary star
        denscomp: density of the companion
    """    
    radiroch = radistar * (2. * densstar / denscomp)**(1. / 3.)
    
    return radiroch