Syndicated accounts are not owned by anyone; they automatically collect content from the source feed. You cannot log into a syndicated account, nor can syndicated accounts be deleted or renamed. Other account types cannot be converted into syndicated accounts, and syndicated accounts cannot be converted into other account types.
However, a syndicated account's external feed URL can be changed by opening a support request
in the Troubleshooting category, making sure to include the username of the feed on LiveJournal and the desired feed URL. Do not create a new syndicated account with the new feed URL as this will complicate making the change.