We present optical and infrared observations of the unusual Type Ia supernova (SN) 2004eo. The light curves and spectra closely resemble those of the prototypical SN 1992A, and the luminosity at maximum is close to the average for a Type Ia supernova (SN Ia). However, the ejected 56Ni mass derived by modelling the bolometric light curve (about) lies near the lower limit of the 56Ni mass distribution observed in normal SNe Ia. Accordingly, SN 2004eo shows a relatively rapid post-maximum decline in the light curve, small expansion velocities in the ejecta and a depth ratio Si ii λ5972/Si ii λ6355 similar to that of SN 1992A. The physical properties of SN 2004eo cause it to fall very close to the boundary between the faint, low-velocity gradient and high-velocity gradient subgroups proposed by Benetti et al. Similar behaviour is seen in a few other SNe Ia. Thus, there may in fact exist a few SNe Ia with intermediate physical properties.
- Galaxies: individual: NGC 6928
- Supernovae: general
- Supernovae: individual: SN 1992A
- Supernovae: individual: SN 2004eo