Time takes for backup observer to become master observer

Hello,

I am looking for any official document on the duration for backup observer automatically to become master observer if there is a failure of the master observer.

We know the default fastStartFailoverThreshold is 30sec, but not sure if the master observer has the same threshold, and if it can be adjusted.

This may be related to the internal heartbeat from observer to data guard databases, but we don't know the heartbeat rate either.

Thank you for sharing your knowledge!

Larry