\documentclass[preprint]{aastex}

\usepackage{natbib}

\title{Sample Paper}
\author{Hannah Jang-Condell}
\begin{document}

\begin{abstract}
The purpose of this document is to illustrate some features of 
AASTeX and BibTeX.
\end{abstract}

\section{Introduction}

AASTeX\footnote{http://aastex.aas.org/} 
is a \LaTeX package used for marking up manuscripts to be 
submitted to the The Astrophysical Journal and 
The Astronomical Journal.  

BibTeX was used to cite sources in \citet{JCT2012}.

Or you could cite a source like so \citep{JCT2012}.  

This is a citation for a book \citep{HKT}.

\bibliographystyle{apj}
\bibliography{mybib}

\end{document}
