By Aruna Viswanatha

WASHINGTON, Dec 26 (Reuters) - U.S. authorities on Wednesday announced charges against a research analyst for trading and tipping others ahead of a 2009 acquisition by computer giant IBM, expanding a related insider trading case filed last month.

Federal prosecutors charged Trent Martin, who worked at a Connecticut brokerage firm, for purchasing shares of SPSS before IBM agreed to the $1.2 billion deal. He was also charged with passing the information to others, including his roommate.

On Nov. 29 the Justice Department and the Securities and Exchange Commission charged two former stockbrokers, including Martin's roommate, for their roles in the alleged insider trading scheme.

The three and others made more than $1 million by trading ahead of the acquisition, prosecutors said.

Martin was specifically named as the source of the information in instant messages between the two brokers, Thomas Conradt and David Weishaus, authorities said.

In a July 2009 message, referring to Martin by name, Conradt wrote: "holy f*** . . . god trent told me not to tell anyone . . . big mistake," according to the indictment unsealed on Wednesday.

Weishaus responded, "eh, we'll get rich."

Martin, an Australian citizen, was arrested on Dec. 22 in Hong Kong, the Justice Department said. Martin could not immediately be reached for comment.

The Securities and Exchange Commission, which filed related civil charges against Martin on Wednesday, said he fled the United States to Australia soon after learning about the SEC's investigation.

IBM agreed to pay $50 per share for SPSS, a 42 percent premium to SPSS' closing price on the day before the purchase was announced.

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