The resolved structure of the extragalactic supernova remnant SNR 4449-1

Journal article, 2013

We present very long baseline interferometry (VLBI) observations of the milliarcsecondscale 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 (λ = 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 × 0.0285 arcsec and 0.8 pc × 0.5 pc) and age (~55 yr) 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 per cent yr-1 and a radio luminosity of 1.74 × 1035 erg s-1. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.