Supernova 2005cn

The eighth SN discovered by BRASS was found on June 19.99 and confirmed through IAUC 8549. The supernova - named SN 2005cn - was located in galaxy NGC 5061, at R.A. 13^o 18' 00.46" and Dec - 26^o 48' 33.1". Its large offset from the galaxy's center was measured as 62" W and 103" N. Apparent magnitude on discovery was estimated as 16.6, unfiltered.

NGC 5061 is an elliptical galaxy (E0 morphological class), with integrated magnitude of 11.4 and dimensions 3.5 x 3.0 arcmin. The galaxy's recession speed (2065 +/- 46 km/s) and redshift (0.00689 +/- 0.00015), both from NED's data, indicate a distance of about 29.5 Mpc, or some 96 million light-years (given a Hubble constant of 70 km/s.Mpc). Assuming that distance as correct, and given our measured apparent magnitude for the supernova, we could estimate its absolute magnitude at discovery as -18.0, which, coupled to the morphology of NGC 5061, appeared to indicate a Type Ia supernova a few days after explosion. This assumption was subsequently confirmed by spectra taken on June 28.21 UT by M. Calkins and R. Hutchins with the 1.5-m telescope of F. L. Whipple Observatory (+ FAST), and reported by M. Modjaz, R. Kirshner, and P. Challis of Harvard-Smithsonian Center for Astrophysics (CBET 173, IAUC 8553). Spectra have shown SN 2005cn as a Type Ia supernova, aged most probably 3 (+/- 2) days after maximum light, and presenting expansion speeds around 10 000 km/s.