A Mestel Cooling-Age Budget for Field White Dwarfs: Ages at Gaia Luminosities and Their Mass Sensitivity

The cooling of a white dwarf is one of the few stellar clocks that runs on simple physics. This paper computes, from stated assumptions and published stellar values, a quantitative budget for the Mestel cooling age using Gaia field white-dwarf masses and luminosities. The headline results are: age 06 1e4 = 8.00; age 06 1e3 = 1.54; age 10 1e4 = 11.52; age 06 1e5 = 41.44. Every number in the abstract and the results section is produced by the deposited computation script from the inputs stated in the Methods, with no fitted parameters beyond those declared. The study is simulated and computed from stated assumptions; it is not a measurement, and its value lies in making the size, sensitivity and failure conditions of the effect explicit enough for observation to confirm or refute.