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Chandra and XMM-Newton imaging and spectroscopic study of the supernova remnant Kes 73 hosting the magnetar 1E 1841-045

We present a Chandra and XMM-Newton study of the supernova remnant (SNR) Kes 73 hosting the anomalous X-ray pulsar 1E 1841-045. The Chandra image reveals clumpy structures across the remnant with enhanced emission along the western rim. The X-ray emission fills the radio shell and spatially correlates with the infrared image. The global X-ray spectrum is described by a two-component thermal model with a column density N_H ~ 2.6e22 cm^{-2} and a total luminosity of L_X ~ 3.3e37 ergs/s (0.5-10 keV, at an assumed distance of 8.5 kpc). The soft component is characterized by a temperature kT_s ~ 0.5 keV, a high ionization timescale, and enhanced Si and S abundances suggesting emission that is dominated by shocked ejecta. The hard component has a temperature kT_h ~ 1.6 keV, a relatively low ionization timescale, and mostly solar abundances suggesting emission that is dominated by interstellar/circumstellar shocked material. A spatially resolved spectroscopy study reveals no significant variations in the spectral properties. We infer an SNR age ranging between 750 yr and 2100 yr, an explosion energy of ~0.3e51 ergs and a shock velocity of 1200 km/s (under the Sedov phase assumption). We also discuss the possible scenario for Kes 73 expanding into the late red supergiant wind phase of its massive progenitor. Comparing the inferred metal abundances to core-collapse nucleosynthesis model yields, we estimate a progenitor mass >20 solar masses, adding a candidate to the growing list of highly magnetized neutron stars proposed to be associated with very massive progenitors.