emulateapj.cls, version 05/12/14 . ... ApJ has moved its publishing to IOP and they have slightly changed the formatting. To implement these changes, call emulateapj with the iop option, use \ documentclass [iop]{ emulateapj } Other available options: [chicago] - (default) typeset as was done in the University of Chicago Press [twocolumn] - (default) two-column mode [onecolumn] - main text in one-column mode [ apj ] - typeset as for main journal [apjl] - (default) typeset as for ...