Sirius XM (SIRI) shares are a three-day tear. The satellite radio company’s shares have jumped 26% in three sessions, and have doubled since mid-June. Today, the stock is up 8 cents, or 14%, to 68 cents. Why this is happening isn’t entirely clear. Technical factors? Short covering? New iPod-related accessories? Or how about takeover rumors? Throw in an improving credit picture for the company, and expectations the company will benefit from higher car sales spurred by the cash for clunkers program, and you have plenty of reasons for the stock to go higher. Just what has the stock moving today, I’m not entirely sure.

If you’ve got a theory, pass it along.