the National Natural Science Foundation of China(19973001); the National 973 Project of China(NKBRAF G19990754)
B-band measurements of 3C273 over some 110 years are compiled and used in a search for periodicities using the Jurkevich method. Periods of 2.0, 13.65±0.20 and 22.5±0.2yr are found. If the long-term periodicity is f...