Characteristic Ages Against Supernova Remnant Ages: What the Discrepancies Require of Magnetar Birth Periods and Braking Histories

A magnetar can be dated by its clock and by its wreckage. The characteristic age from spin-down assumes a millisecond birth and steady dipole braking; the remnant age comes from the expansion of the shell the birth explosion left behind. For several sources the two dates disagree by more than an order of magnitude, and the disagreement itself carries information about birth periods and braking. Working from published values for the sources concerned, this paper computes the relevant quantities under one stated set of conventions and compares them source by source. Headline results: largest age ratio source 1E 2259+586; largest age ratio 16.5; smallest age ratio 0.02; sources tau c exceeds remnant by 10x 1. The comparisons are budget statements: they establish whether the energies, stresses, powers and timescales involved are mutually consistent, and by what margin. Every number quoted is produced by the deposited compute.py script from the stated inputs, and the full per-source record is deposited as results.json alongside the text.