What are the requirements according to Vaticanologists or other Church officials to be considered papabile?

What are the requirements according to Vaticanologists to be considered papabile? If in fact such requirements actually exist. [Papabile](https://en.m.wikipedia.org/wiki/Papabile) is an unofficial term, first coined by Vaticanologists for someone is thought to be a possible candidate to be elected pope. I do not limit this question to Vaticanologists alone, but to all other Church officials or theologians who take into account the possibility of naming someone papabile seriously and gives reasons for doing so, especially now that the Holy See is in a moment of ***Sede Vacante***.