The brightness of SN 1991T and the uniformity of decline-rate and colour corrected absolute magnitudes of supernovae Ia

We present a distance to NGC 4527, the host galaxy of the type 1a SN 1991T, measured by surface brightness fluctuations. This supernova has been label led "peculiar" both on the grounds of its spectroscopic behaviour and its a pparent overluminosity with respect to other supernovae. The distance modul us to DGC 4527 and thus to SN 1991T is 30.26 +/- 0.09. This relatively shor t distance largely removes the discrepancy with other la supernovae having similar light-curve characteristics and also removes the motivation for int erpreting SN 1991T as a super-Chandrasekhar explosion. However, the reddeni ng uncertainty results in significant uncertainty of the absolute magnitude s. We show further that: although the intrinsic absolute magnitudes among I a supernovae are quite different, their brightness, corrected for decline-r ate and colour, shows a high degree of uniformity, including underluminous events like SN 1991bg and SN 1997cn. In particular, the present data do not support a significant difference between corrected SNe Ia luminosities in late-type and early-type host galaxies.