How to change the weight of a pin line in PGF Plots?

Question

Using pins is a nice way to annote your plots in PGF Plots. However, I would like to have the weight for the line leading from a point on the graph to the text to be bold. How do I do this?

Consider the following MWE:

\documentclass{minimal}
\usepackage{pgfplots}
    \pgfplotsset{compat=1.5.1}

\begin{document}
\begin{tikzpicture}
    \begin{axis}
        \addplot[domain=1:6]
        {exp(x)};
        54.59815
        \node[coordinate,pin=left:{A pin!}]
            at (axis cs:4,54.59815) {};
    \end{axis}
\end{tikzpicture}
\end{document}

Answer 1

To modify a single pin, you can use pin edge:

\documentclass{article}
\usepackage{pgfplots}
    \pgfplotsset{compat=1.5.1}

\begin{document}
\begin{tikzpicture}
    \begin{axis}
        \addplot[domain=1:6]
        {exp(x)};
        54.59815
        \node[coordinate,pin={[pin edge={blue,ultra thick}]left:{A pin!} } ]
            at (axis cs:4,54.59815) {};
    \end{axis}
\end{tikzpicture}
\end{document}

To change the format for all pins, you can change the every pin edge style.