Persistent Emitting Areas of Magnetars: Blackbody Radii from Quiescent Luminosities and Temperatures

Quiescent magnetar spectra are routinely fitted with thermal components whose temperature and luminosity jointly fix an emitting area. That area is rarely compared across sources in one place. Doing so shows whether the glow comes from the whole surface, from a heated cap, or from a region so small that a localised heating source is unavoidable. 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: smallest emitting radius source 1E 1841-045; smallest emitting radius km 1.93; largest emitting radius km 5.36; sources area below full surface 8. 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.