Subprime

The reaction to the Citigroup and UBS news might indicate that investors were expecting a lot worse.
Moreover, the news puts forth more information related to the subprime, suggesting some uncertainty is removed.
As you can see on the 2 charts below, those stocks are trying to rebound (base building) from a very oversold situation.(lots of green arrows)
Strong volumes may also indicate an accumulation phase.
Finally, yesterday was the start of the fourth quarter, a bullish seasonal period for stock.