THE PROPERTIES OF THE PROGENITOR SUPERNOVA, PULSAR WIND, AND NEUTRON STAR INSIDE PWN G54.1+0.3

The evolution of a pulsar wind nebula (PWN) inside a supernova remnant (SNR) is sensitive to the properties of the central neutron star, pulsar wind, progenitor supernova, and interstellar medium. These properties are both difficult to measure directly and critical for understanding the formation of neutron stars and their interaction with the surrounding medium. In this paper, we determine these properties for PWN G54.1+0.3 by fitting its observed properties with a model for the dynamical and radiative evolution of a PWN inside an SNR. Our modeling suggests that the progenitor of G54.1+0.3 was an isolated ∼15-20M⊙ star which exploded inside a massive star cluster, creating a neutron star initially spinning with a period of P₀ ∼ 30-80 ms. We also find that ≳99.9% of the pulsar's rotational energy is injected into the PWN as relativistic electrons and positrons whose energy spectrum is well characterized by a broken power law. Finally, we propose future observations which can both test the validity of this model and better determine the properties of this source - in particular, its distance and the initial spin period of the central pulsar.