We present very long baseline interferometry ( VLBI ) observations of the milliarcsecond-scale radio structure of the supernova remnant SNR 4449 - 1 in the galaxy NGC 4449 .
This young and superluminous remnant was observed at 1.6 GHz ( \lambda = 18 cm ) with the European VLBI Network .
The observations confirm earlier identifications of this object with a supernova remnant ( SNR ) while revealing a somewhat different morphology compared with the structure reported by Bietenholz et al .
from VLBI observations at 1.4 GHz .
This difference is discussed here in the context of structural sensitivity of both observations .
The 1.6 GHz image yields accurate estimates of the size ( 0.0422 arcsec \times 0.0285 arcsec and 0.8 \times 0.5 pc ) and age ( \sim 55 yr ) of SNR 4449 - 1 .
With a total flux of 6.1 \pm 0.6 mJy measured in the VLBI image , the historical lightcurve of the source can be well represented by a power-law decay with a power index of - 1.19 \pm 0.07 .
The SNR exhibits a decline rate of the radio emission of 2.2 \% \pm 0.1 \% yr ^ { -1 } and a radio luminosity of 1.74 \times 10 ^ { 35 } erg s ^ { -1 } .