The Royal Bank of Scotland was fined $50 million by a federal judge in Connecticut , part of more than $600 million in penalties announced last year for manipulating interest rates. The bank’s subsidiary, RBS Securities Japan, agreed to pay the fine last year as part of a plea agreement and a judge in U.S. District Court in Hartford approved the penalty. The subsidiary pleaded guilty last April to wire fraud and admitted its role in manipulating the Japanese Yen London interbank offered rate, or LIBOR. That’s the rate that banks use to lend money to each other and provides the basis for trillions of dollars in contracts around the world. U.S. and U.K. regulators and authorities fined RBS $612 million, including the latest $50 million fine, for rate-rigging. The investigations found wrongdoing by about 20 RBS traders, according to court papers. Prosecutors and the company say those responsible have left the company and others were disciplined. RBS was one of several banks fined for manipulating LIBOR.