There is only one file type that uses the .WIXOBJ extension:
WiX Object File
Object file created by the WiX toolset, a Windows installer developing program; contains multiple sections that hold symbols and references to other symbols; comprised of <table>, <row>, and <field> elements holding data that is placed into the Windows Installer database; created when each WiX Source file is compiled.
NOTE: WiX Source (.WXS) files are preprocessed and compiled into WIXOBJ files by the Candle tool in the WiX Toolset.
Updated: December 4, 2013