Supernova Rate in the Milky Way

In order to estimate the supernova rate in our Galaxy, two sources are considered: (1) The supernova rate in other galaxies; (2) The few historical observed supernovae in the Milky Way. To estimate the supernova rate in external galaxies, a fiducial sample of 96 supernovae is used, subdivided and classified as follows: 11 Type Ia supernovae, which are assumed to come from white dwarfs, belonging to a old stellar population and 7 Type Ib and 78 Type II supernovae, which are assumed to come from gravitational stellar collapse of massive stars, belonging to young star population [#!tammann!#].

The supernova rate is affected by several features, which must be taken into account: (1) The high central brightness of the galaxies which can obscure supernova detection, implies an increase of the supernova rate with the distance. (2) The supernova rate observed depends also on the inclination of spiral parent galaxies. (3) The supernova rate is expected to be proportional to the number of progenitor stars in a galaxy. (4) It depends further on the galaxy luminosity and its Hubble type. Our Galaxy is expected to be of type Sbc [#!tammann!#].

From the five historical Galactic supernovae in the last millennium a global rate can be derived, using a detailed model of the Milky Way. A Galactic model consists of a thin stellar disk, which represents the young stellar population, and of a thick stellar disk as well as of a halo, which contains most of the old stars. Therefore it is expected, that supernovae Type II and Ib are located in the thin disk, while the Type Ia supernovae are thought to be located in the thick disk. Results from these considerations give an expectation of 39 Galactic supernovae in 1000 yr to explain the only five observed [#!tammann!#].

Combining the results from all information of these two sources, one gets a rate of $2.5 \pm 0.8$ SNe per 100 yr, which means one galactic supernova per $40 \pm 13$ yr [#!tammann!#]. Note that $\sim 85 \%$ of these supernova come from massive stars, which are progenitors for Type II, Ib SNe. In other words, a Galactic neutrino burst is expected every $47 \pm 15$ yr, which means $2.1 \pm 0.7$ per century.