Tuesday was an upbeat day on Wall Street as major market benchmarks climbed a small fraction of a percent despite ongoing nervousness about the future of the U.S. economy. The Federal Reserve began its two-day meeting to discuss interest rates, but investors seemed as if they'd be happy just having an answer to the question of whether the central bank will be fast or slow in boosting rates in the near future.

Even though the overall market stayed relatively quiet, some individual stocks soared higher as merger and acquisition activity picked up. Among the top performers on the day were DTS (NASDAQ:DTSI), SolarCity (NASDAQ:SCTY.DL), and Tobira Therapeutics (NASDAQ: TBRA).

Image source: SolarCity.

Everyone's hearing DTS now

DTS jumped 23% after the audio technology company agreed to a buyout from Tessera Technologies (NASDAQ:XPER) this morning. Tessera will pay $42.50 in cash for DTS, and it believes the combination will benefit from complementary products given Tessera's emphasis on imaging technology. Going forward, product licensing will remain a key element of the post-merger company's business, with Tessera expecting almost half of its post-merger revenue for this year to come from licensing its products. As DTS CEO Jon Kirchner explained it, he believes the merger will allow the companies "to deliver the world's leading audio and imaging solutions to all of our key markets and drive meaningful value for our combined customers, partners, and employees."

With shares climbing to within 1% of the buyout price, investors are taking the buyout as a done deal -- and perhaps even hoping for a higher bid from a rival.

SolarCity gets out of the shade

SolarCity rose 7% despite facing increasing controversy governing its proposed merger with Tesla Motors (NASDAQ:TSLA). Shareholders have sued Tesla, arguing that its board of directors has violated fiduciary duties to investors by agreeing to the SolarCity deal. Tesla has warned that a delay in the deal could result from the litigation, especially if the plaintiffs in the case obtain injunctions preventing the closing of the merger from taking place. Nevertheless, SolarCity investors seem to be encouraged by the positive tone Tesla has taken in maintaining its resolve to get the deal done, arguing that the shareholder lawsuits are without merit, and saying that it expects to move forward. With the value of the Tesla bid being almost 25% higher than where SolarCity currently trades, some traders in SolarCity shares believe there's enough margin of safety to justify speculative positions in the stock.

Tobira comes out of nowhere

Finally, Tobira Therapeutics soared by a whopping 720%. The nearly unknown biotechnology company received a surprise bid from Allergan (NYSE:AGN), which offered to pay as much as $1.7 billion for the tiny company. Tobira shareholders will receive $28.35 per cash upfront, along with contingent value rights that could be worth almost $50 per share more if the company is successful in reaching certain milestones. Tobira's emphasis on non-alcoholic steatohepatitis and other liver diseases should fit well with Allergan's existing pipeline, but most investors are completely confused about why the company was worth what Allergan bid. Nevertheless, Tobira investors are getting a little-expected jackpot today, with the potential for even more success if its drug candidates prove to be effective in the future.

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