NEW YORK — When the pop singer Laura Branigan died, The Associated Press, relying on information from her management company, reported in an obituary on Aug. 28, 2004, that she was 47 and had been born on July 3, 1957. After being contacted recently by one of Branigan’s fans, however, the AP conducted a thorough review and established that she had actually been 52 when she died. School records, newspaper articles written about her in the 1950s and 1960s, and testimonials from childhood friends all indicate she was born in 1952.