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# The preamble of your TEX file

\documentclass{aa}

To get the standard A&A 2-column-layout (i.e. single-line spacing), you have to include this command at the beginning of your article.

\documentclass[referee]{aa}

Both for refereeing purposes and, after acceptance, for language editing purposes, the authors are requested to send their article in "Referee format", i.e. with a special double-line spacing layout. To set this class option, please include the referee option. This special layout also provides a list of all astronomical objects indexed with the \object command.

\documentclass[letter]{aa}

There is a special layout for Letters. The mention "Letter to the Editor" is automatically added.

\documentclass[longauth]{aa}

In articles that are the result of consortia, the number of authors and the list of affiliations are very long. With the longauth option, all the institutes are set below the references.

\documentclass[onecolumn]{aa}

Some papers contain a lot of large mathematical formulae that are sometimes cannot be read easily and cannot be written in a 2-column format. In this case, the authors can submit their articles using the option onecolumn. After the submission, the editors will confirm that the article will actually be displayed in 1 column, right across the page.

\documentclass[bibyear]{aa}

If you don't use structured references (according to the author-year natbib style), add this option.

## TX fonts

A&A uses the Postscript TX Times-fonts. The TX fonts consist of virtual text roman fonts using Adobe Times with some modified and additional text symbols. The TX fonts are distributed under the GNU public license and are available in the distributions of LaTeX since December 2000.

 \documentclass{aa} \usepackage[varg]{txfonts} ... \begin{document} 

As the use of the TX fonts results in a slightly different page make-up from CM fonts, we encourage you to use TX fonts, following this example.