Vol. 552
In section 6. Interstellar and circumstellar matter

Chandra observation of the Galactic supernova remnant CTB 109 (G109.1-1.0)

The authors present a comprehensive study of the ionization, thermal structure, and abundance distribution of this important supernova remnant CTB 109. The remnant has heretofore been known only from the shocked interstellar gas. This was because the ejected matter from the event, which also produced an anomalous XR pulsar, had not been detected previously. The authors present a lovely set of maps of the Si and Mg distributions, derived from narrow band imaging using ACIS/Chandra, analyzed using a two-component nonequilibrium ionization model (shocked interstellar gas plus ejecta). They also derive the filling factor for the ejecta and propose a minimum mass of about 20 M_solar. This argues strongly against a SN Ia for the progenitor. There is significant differentiation of the two elements, with Mg being more broadly distributed. They also propose that there is ongoing interaction with the co-located CO molecular cloud, in agreement with HE gamma-ray observations with Fermi, and that another cloud was evaporated in the process and mixed into a portion of the ejecta.