Agnes Tachyon, the leading sire in Japan in 2008 and the best son of Sunday Silence to stand at stud, died of heart failure Monday night at Shadai Stallion Station in Hokkaido at the age of 11. "I am shocked into silence because his death has come so suddenly," said Shadai owner Teruya Yoshida. Out of Japanese 1000 Guineas winner Agnes Flora and a half brother to Japanese Derby winner Agnes Flight, Agnes Tachyon won the 1 1/4-mile Satsuki Sho, or Japanese 2000 Guineas, in 2001, after which a bowed tendon put a premature end to his racing career. Sent to the Yoshida brothers' Shadai Stallion Station, he sired the outstanding filly Daiwa Scarlet, herself the winner of the Japanese 1000 Guineas as well as the 1 9/16-mile Arima Kinen, the 1 3/8-mile Queen Elizabeth II Commemorative Cup, and the 1 1/4-mile Shuka Sho, all Grade 1 contests or their equivalent. His best son to date is Deep Sky, the winner of the 2008 Japanese Derby and the NHK Mile Cup who will run in Sunday's Takarazuka Kinen at Hanshin. Agnes Tachyon is also the sire of Japanese 2000 Guineas winner Captain Thule and Queen Elizabeth II Commemorative Cup winner Little Amapola.