
Supernovae put out 10^53 or 10^54 (i forget which, but it's only an
order of magnitude...).  Not in gamma rays, though.  You'd hafta get
all of that into gammas if they were at 9 Mpc, but if a decent fraction
of the SN output was in gammas it could reasonably be extragalactic 
(but closer than 9 Mpc).  I dunno SN theory so well, but I can't think
of how to get many gammas out.  Maybe I should look it up.

Big radio galaxies can put out 10^46 erg/s *continually*.  That's just
in the radio... there are a lot of gammas around them, too, but "bursts"?
Nah.

Neither of these should be taken as explanations... just trying to show
that those energies *are* produced by things we know about.
