This paper estimates the relative frequency of different types of core-collapse supernovæ , in terms of the ratio \mathcal { S } between the number of type Ib–Ic and of type II supernovæ .
We estimate \mathcal { S } independently for all normal and Seyfert galaxies whose radial velocity is \leq 14000 km s ^ { -1 } , and which had at least one supernova event recorded in the Asiago catalogue from January 1986 to August 2000 .
We find that the ratio \mathcal { S } is \approx 0.23 \pm 0.05 in normal galaxies .
This value is consistent with constant star formation rate and with a Salpeter Initial Mass Function and average binary rate \approx 50 % .
On the contrary , Seyfert galaxies exceed the ratio \mathcal { S } in normal galaxies by a factor \approx 4 at a confidence level \ga 2 \sigma .
A caveat is that the numbers for Seyferts are still small ( 6 type Ib-Ic and 6 type II supernovae discovered as yet ) .
Assumed real , this excess of type Ib and Ic with respect to type II supernovae , may indicate a burst of star formation of young age ( \tau \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } 20 Myr ) , a high incidence of binary systems in the inner regions ( r \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } 0.4 R _ { 25 } ) of Seyfert galaxies , or a top-loaded mass function .