What is the fine-grained topic of the following text: At the end of 2013, Sirius reorganized their corporate structure, which made Sirius XM Radio Inc. a direct, wholly owned subsidiary of Sirius XM Holdings, Inc. Sirius XM Radio was formed after the U.S. Federal Communications Commission approved the acquisition of XM Satellite Radio Holding, Inc. by Sirius Satellite Radio, Inc. on July 29, 2008, 17 months after the companies first proposed the merger. Only return the topic.
Reorganization and Acquisition of Sirius XM Radio Inc.