Chart of the day: Apple shares spike suddenly on high volume

No hard news, just rumors of a large buyback or special dividend

Click to enlarge.

FORTUNE -- After trading down all day -- and all year, for that matter -- Apple (AAPL) began moving higher at 2:26 p.m. Monday and didn't stop until it hit resistance at $438. The stock closed at $437.87, up $6.15 (1.42%) for the day.

Wall Street watchers were left scratching their heads.

• "What's up with AAPL?" was the headline on Barrons.
• "Apple Spikes on ... What Exactly?" quoth the Wall Street Journal
• "Apple Suddenly Popped And No One Knows Why" was the first take at Business Insider, followed within the hour by...
• "Noooooo, Apple! Don't Do A Special Dividend! Buy Back $50 Billion Of Stock!," with Henry Blodget's take on the rumors he's heard