\begin{tikzpicture}
% lambda = 1/3
  \begin{axis}[
    width=1.8in,
    height=2.5in,
    axis lines=center,
    xlabel=\empty,
    ylabel=\empty,
    % xticklabel=\empty,
    % yticklabel=\empty,
    ylabel style={above right},
    xlabel style={below right},
    xtick={0,2},
    ytick={0,-2,2},        
    xmin=-0.5,xmax=3.5,ymin=-4,ymax=4]
    % x equation
    \addplot+[no markers, samples=200, samples y=0, domain=0:2, variable=\t, line width=1.3, color = cb-green]
    ({t}, {sqrt(2*t-t^2)/sqrt(1/3)});
    \addplot+[no markers, samples=200, samples y=0, domain=0:2, variable=\t, line width=1.3, color = cb-green]
    ({t}, -{sqrt(2*t-t^2)/sqrt(1/3)});
    % \draw[cb-green, line width = 1.3] (0,-11.8) -- (0, 11.6);

    % y equation
    \addplot+[no markers, samples=200, samples y=0, domain=-4:4, variable=\t, line width=1.3, color = cb-purple]
    ({(6 - 1/9*t^2)/(2)}, {t});
    % \addplot+[no markers, samples=200, samples y=0, domain=-sqrt(8):sqrt(8), variable=\t, line width=1.3, color = cb-purple]
    % ({t}, {-2*sqrt(3)*sqrt(8 - t^2)});
    \draw[cb-purple, line width = 1.3] (-0.45,0) -- (3.4,0);

    % highlight intersections
    \addplot [only marks, mark=x, line width = 1.3, mark size = 3pt] table {
    0  0
    % 2.44949  0
    % -2.44949  0
    % 0  9.79796
    % 0  -9.79796
    };
    \addplot [only marks, mark=square*, mark size = 2pt] table {
    2  0
    };

    \node at (1,-3.2) [rectangle,draw,fill = cb-palegrey,inner sep=0.8pt] {$\lambda = \frac{1}{3}$};
    \end{axis}
\end{tikzpicture}
\,
\begin{tikzpicture}
% lambda = 1
  \begin{axis}[
    width=1.8in,
    height=2.5in,
    axis lines=center,
    xlabel=\empty,
    ylabel=\empty,
    % xticklabel=\empty,
    % yticklabel=\empty,
    ylabel style={above right},
    xlabel style={below right},
    xtick={0,2},
    ytick={0,-2,2},        
    xmin=-0.5,xmax=3.5,ymin=-4,ymax=4]
    % x equation
    \addplot+[no markers, samples=200, samples y=0, domain=0:2, variable=\t, line width=1.3, color = cb-green]
    ({t}, {sqrt(2*t-t^2)/sqrt(1)});
    \addplot+[no markers, samples=200, samples y=0, domain=0:2, variable=\t, line width=1.3, color = cb-green]
    ({t}, -{sqrt(2*t-t^2)/sqrt(1)});
    % \draw[cb-green, line width = 1.3] (0,-11.8) -- (0, 11.6);

    % y equation
    \addplot+[no markers, samples=200, samples y=0, domain=-4:4, variable=\t, line width=1.3, color = cb-purple]
    ({(6 - 1*t^2)/(6)}, {t});
    % \addplot+[no markers, samples=200, samples y=0, domain=-sqrt(8):sqrt(8), variable=\t, line width=1.3, color = cb-purple]
    % ({t}, {-2*sqrt(3)*sqrt(8 - t^2)});
    \draw[cb-purple, line width = 1.3] (-0.45,0) -- (3.4,0);

    % highlight intersections
    \addplot [only marks, mark=x, line width = 1.3, mark size = 3pt] table {
    0  0
    2  0
    % 2.44949  0
    % -2.44949  0
    % 0  9.79796
    % 0  -9.79796
    };
    \addplot [only marks, mark=square*, mark size = 2pt] table {
    0.837722  0.986745
    0.837722  -0.986745
    };

    \node at (1,-3.2) [rectangle,draw,fill = cb-palegrey,inner sep=1.5pt] {$\lambda = 1$};
    \end{axis}
\end{tikzpicture}