\documentstyle{preprint}
\input pub.sty
\begin{document}

\title{ON THE OBSERVATIONAL EVIDENCE FOR ACCRETION DISKS\\
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IN ACTIVE GALACTIC NUCLEI}

\author{Mario Livio and Chun Xu\\
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Space Telescope Science Institute\\
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3700 San Martin Drive\\
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Baltimore, MD 21218}

\pub{The Astrophysical Journal}

\maketitle

\begin{abstract}

We show that the double-peaked emission lines that are observed in the active
galaxy 3C~390.3 {\it cannot\/} be produced by two line-emitting streams (generated 
by a two-sided jet).  The reason for this is the fact that, as we show, the emitting 
region on the receding jet is obscured from view by the accretion disk. This leaves 
the accretion disk as the only viable site for the production of these lines.
\end{abstract}