2013MNRAS.436.2454M

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 1.6GHz (λ = 18cm) 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 1.4GHz. This difference is discussed here in the context of structural sensitivity of both observations. The 1.6GHz image yields accurate estimates of the size (0.0422arcsecx0.0285arcsec and 0.8pcx0.5pc) and age ( ∼ 55yr) of SNR 4449-1. With a total flux of 6.1±0.6 mJy measured in the VLBI image, the historical light curve of the source can be well represented by a power-law decay with a power index of -1.19±0.07. The SNR exhibits a decline rate of the radio emission of 2.2±0.1 percent/yr and a radio luminosity of 1.74x10³⁵erg/s.