ar X iv : a st ro - p h / 05 03 18 0 v 1 8 M ar 2 00 5 Monitoring of the prompt radio emission from the unusual supernova 2004 dj in NGC 2403

Supernova 2004dj in the nearby spiral galaxy NGC2403 was detected optically in July 2004. Peaking at a magnitude of 11.2, this is the brightest supernova detected for several years. Here we present Multi-Element Radio Linked Interferometer Network (MERLIN) observations of this source, made over a four month period, which give a position of R.A. = 073717.044, Dec = +653557. 84 (J2000.0). We also present a well-sampled 5GHz light curve covering the period from 5 August to 2 December 2004. With the exception of the unusual and very close SN 1987A, these observations represent the first detailed radio light curve for the prompt emission from a Type II-P supernova. Subject headings: supernovae: individual (2004dj) — galaxies: starburst — radio continuum: supernovae