The Vela Supernova Remnant: Sedov Energy, Swept Mass and the Radiative Horizon

This paper computes the energy, density and acceleration budgets of the Vela remnant from a small set of adopted, published input values, using the relations stated in the Methods and a deposited script that reproduces every number. The Sedov shock speed is 686 km/s, well below the free-expansion value of 1.72e+03 km/s, giving a deceleration parameter of 0.4 exactly as the self-similar solution requires for a remnant deep in this phase. The blast-wave energy is 1.11 in units of 10^51 erg at the adopted mean density, a factor 1.11 of the canonical 10^51 erg, which shows that Vela's large size does not demand an unusually energetic explosion once its low-density environment is admitted. The calculation is a computation from stated assumptions, not a measurement, and each headline result is reported together with the diagnostic that tests whether the assumed evolutionary phase applies to this object.