2002ApJ...569..275M

We present the first results of an XMM-Newton observation of the central X-ray source in the Cas A supernova remnant. The spectrum can be fitted equally well with an absorbed steep power law (α_ph∼3, N_H∼1.5x10²² cm^–2) or with a bremsstrahlung with temperature kT∼2.4 keV and N_H∼10²² cm^–2. A blackbody model (kT_BB∼0.7 keV) gives a slightly worse fit and requires a column density N_H∼5x10²¹ cm^–2 and an emitting area with radius ∼0.3 km (for d=3.4 kpc). A search for pulsations for periods longer than 150 ms gave negative results. The 3 σ upper limits on the pulsed fraction are ∼13% for P>0.3 s and ∼7% for P>3 s. The overall properties of the central X-ray source in Cas A are difficult to explain in terms of a rapidly spinning neutron star with a canonical magnetic field of ∼10¹² G, and are more similar to those of slowly rotating neutron stars such as the anomalous X-ray pulsars.