Is Torbjorn's turret destroyed upon death?

I don't have a source for this besides personal experience, but Torbjörn's turret will remain upon death. It is only destroyed if you setup a new one, the enemy destroys it, or you switch heroes.

No, but also yes.

Torbjorn's turret will not be destroyed if you kill the Torbjorn while he has a functional turret. However, if you kill Torbrjon as his turret is building (build animation and gaining health from 0-150), then his newly placed turret will also be destroyed.

Source at 1:11