Evolution of the radio spectrum of Cassiopeia A from long-term observations. Observations at 290 and 927 MHz

Long-term measurements of the radio flux density of the young supernova remnant Cassiopeia A relative to the radio galaxy Cygnus A have been carried out at 290 and 927 MHz. We have obtained for the mean rates of the secular decrease of the radio emission of Cassiopeia A d(290 MHz) = -0.67 +/- 0.04% year(-1) for 1978-2005 and d(927 MHz) = -0.71 +/- 0.035% year(-1) for 1977-2004. The evolution of the radio spectrum of Cassiopeia A is traced based on long-term observations at 38, 151.5, 290, 927, and 2924 MHz.