A study of composite supernova remnants

We present a study of composite supernova remnants (SNRs) and the detailed description of two of them, each one a good example of the two classes of composite SNRs. W44 is a thermal-dominated SNR with a shell-like morphology in the radio band and a distinctly peaked centered one in the X-ray. We have analyzed two different models to explain this particular X-ray-emission spatial distribution. In addition, we have for the first time detected the X-ray synchrotron nebula associated with the radio pulsar PSR B1853+01 located within the boundaries of the SNR.; MSH 11-62 is a power-law-dominated remnant but no pulsar associated with the remnant has been detected until now. We have isolated the point-like source of high-energy emission coming from this SNR and deduce from the spectral analysis some characteristics of the pulsar yet to be detected in the radio band.; Both of these SNRs present the characteristic of the center-filled remnants in contradiction with the standard scenarios of supernova evolution although they are very different from each other. It is very likely that W44 gets its centered-peaked profile from the dominating radiative losses as it is probably entering the radiative phase of standard supernova evolution, while MSH 11-62 gets its from the yet undetected radio pulsar most probably present at the center of the synchrotron emission detected. In addition, we have presented data on a middle age pulsar with no remnant counterpart but for which we detect synchrotron emission in much the same way that the emission is detected for MSH 11-62.