Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of oil and gas refiner Sunoco (NYSE: SUN) surged 19% on Monday after pipeline operator Energy Transfer Partners (NYSE: ETP) announced it will acquire the company for about $5.3 billion.

So what: The deal values Sunoco at $50.13 per share and represents a juicy 23% premium to its closing price on Friday. Energy Transfer is making the move primarily to diversify into oil pipelines in response to the prolonged natural gas slump, and judging by its own stock's 3.5% rally, Wall Street seems pleased with the strategy.   

Now what: The deal is expected to close in the third or fourth quarter -- pending shareholder and regulatory approval -- and should contribute to Energy Transfer's earnings right away. "This transaction, which will be immediately accretive, represents the next step in Energy Transfer Partners' transformation into a more diversified enterprise with an integrated and expanded footprint," said Energy Transfer Chairman and CEO Kelcy Warren. So while Sunoco shares might be all popped out, Energy Transfer remains a five-star stock worth checking out. 

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