Not definitive? There is a hey in front of the noun, isn't there? What am I missing?
When do we pronounce the definite article ה as ha- / ah- / hé-( I think this one passed before, but I'm not sure)
Always "ha". The Hebrew h sound is pretty weak, so can sound like "a" at times.
In "proper" speech it can be "he" before guttural consonants (ע/ח), but no one says it like that unless they're trying to be very formal.