XMM-Newton Observations of the Galactic Supernova Remnant CTB 109 (G109.1–1.0)

We present the analysis of the X-ray Multimirror Mission (XMM-Newton) European Photon Imaging Camera (EPIC) data of the Galactic supernova remnant (SNR) CTB 109 (G109.1-1.0). CTB 109 is associated with the anomalous X-ray pulsar (AXP) 1E 2259+586 and has an unusual semicircular morphology in both the X-ray and the radio and an extended X-ray bright interior region known as the "Lobe." The deep EPIC mosaic image of the remnant shows no emission toward the west where a giant molecular cloud complex is located. No morphological connection between the Lobe and the AXP is found. We find remarkably little spectral variation across the remnant given the large intensity variations. All spectra of the shell and the Lobe are well fitted by a single-temperature nonequilibrium ionization model for a collisional plasma with solar abundances [kT ≈ 0.5-0.7 keV, τ = n_e dt ≈ (1-4) × 10¹¹ s cm^-3, N_H ≈ (5-7) × 10²¹ cm^-2]. There is no indication of nonthermal emission in the Lobe or the shell. We conclude that the Lobe originated from an interaction of the SNR shock wave with an interstellar cloud. Applying the Sedov solution for the undisturbed eastern part of the SNR and assuming full equilibration between the electrons and ions behind the shock front, the SNR shock velocity is derived as v_s = 720 ± 60 km s^-1, the remnant age as t = (8.8 ± 0.9) × 10³d₃ yr, the initial energy as E₀ = (7.4 ± 2.9) × 10⁵⁰d ergs, and the preshock density of the nuclei in the ambient medium as n₀ = (0.16 ± 0.02)d cm^-3, at an assumed distance of D = 3.0d₃ kpc. Assuming that CTB 109 and 1E 2259+586 are associated, these values constrain the age and the environment of the progenitor of the SNR and the pulsar.