Supernova 2005cb

SN 2005cb, our seventh discovery, was found on 2005 May 13.22. Confirmation from IAU came on IAUC 8530. The supernova was located in the galaxy NGC 6753, more precisely at R.A 19^o11'23.6" and Dec – 57^o 02' 58". Its offset from the center of the galaxy was 16” W and 19” N. Apparent (unfiltered) magnitude was measured as 15.6 on the day of discovery.

NGC 6753 is a Southern spiral galaxy belonging to the SA(r)b morphological class. Its apparent integrated magnitude reaches 12.0 and its dimensions are 2.5 x 2.1 arcmin. Given its measured recession speed (3124 +/- 26 km/s) and redshift (0.01042 +/- 0.00009), both from NED data, we can estimate its distance as roughly 44.6 megaparsecs (or some 145 million light years), assuming a Hubble constant of 70 km/s.Mpc.

Absolute magnitude of SN 2005cb on its discovery was calculated based on our own photometric measures and on NED data, resulting on Mv = –17.8, which seems to be quite compatible with a supernova a few days after explosion. Spectra taken on May 19.76 UT by Davis, Anderson and Schmidt from Australian National University with the ANU 2.3-m telescope have shown SN 2005cb to be a Type Ic supernova about one week past maximum.