As the president says, Congress authorized the spending; Congress can also authorize lower spending in the future. The Constitution states that all spending bills originate in the House; the Speaker of the House may have some say.
The executive branch can prioritize which legal obligations (authorized by Congress and signed by the president) it chooses to pay with funds on hand. Congress has not authorized any funds for the 2014 year to date, Oct. 6, for any department except some for the Department of Defense (the first priority of the federal government), Department of Homeland Security and Veterans. What funds would be available? Funds left over from prior years and current tax receipts. Social Security, Medicare, treasury bills, notes and bonds are some of the legal obligations that current tax receipts would easily cover and would be a debt default.
The talk of a catastrophe by the administration, Democratic leaders, liberal talking heads, etc., are scare tactics if they are telling you it will happen around the middle of October without telling you about the above paragraph. This stalemate could go on for a few months or the president could opt for a catastrophe at any time; his Treasury Secretary manages the numbers and the debt limit could have occurred in June or July of 2013 if he had funded the federal pensions and some other funds management. The administration chose to show a smaller federal deficit for 2013 under the unified budget and can choose the default time.
The executive editor of the Aiken Standard has the authority to change the title of this letter (to one she thinks is more fitting) and to cut the letter into one sentence paragraphs if she needs to space out the editorial page and may have done so.