If I have the following button in an html file
According to official event is of type Object, also in my case when i typecaste event to the Object it does't throw any error, but after reading documentation of angular2 found event is of type EventEmitter so you can type caste your event into EventEmitter
see here is plunkr for the same http://plnkr.co/edit/8HRA3bM0NxXrzBAjWYXc?p=preview
for more info refer here https://angular.io/docs/ts/latest/guide/template-syntax.html#!#event-binding