How is the relationship between a star's initial mass and its core temperature characterized?

It is far more aggressive than linear, tending toward exponential rise

The correlation between a star's starting mass and the resulting core temperature is not a simple, gentle relationship where doubling the mass doubles the temperature. Instead, the text specifies that this relationship is far more aggressive. For more massive objects, the required outward pressure needed to maintain hydrostatic equilibrium against increased gravity rises sharply. Therefore, even a star with only a few times the mass of the Sun can possess a core temperature substantially higher than $15$ million K, reflecting this steep, almost exponential dependency where greater mass demands disproportionately higher internal heat resistance.