2007AJ....133.2156L

The luminous, oxygen-rich supernova remnant J1228+441 is located in the irregular galaxy NGC 4449 and has been observed at radio wavelengths for 30 years. An analysis of recent Very Large Array (VLA) observations of NGC 4449, combined with VLA archive data and previously published VLA and Westerbork Synthesis Radio Telescope observations, yields light curves at 6 and 20 cm from 1972 to 2002. The light curves at all radio frequencies exhibit a marked decline in radio emission, confirming past findings. This paper presents and discusses the radio light curves and spectral index α variations from 1972 to 2002, where S_ν∝ν^–α, and compares J1228+441 with other radio supernovae. The spectral index of J1228+441 appears to have steepened in the last 5 years at higher frequencies, from α=0.64±0.02 in 1996 to α=1.01±0.02 in 2001-2002.