The spectacular ``first light'' observation with the Chandra X-Ray Observatory revealed an X-ray point source near the center of the 300 yr old Cassiopeia A supernova remnant. We present an analysis of the public X-ray spectral and timing data from Chandra. The Chandra/ACIS spectrum of the point source can be fit with an ideal blackbody model (kT=0.5 keV), or with blackbody models modified by the presence of a neutron star atmosphere (kT=0.25-0.35 keV), but the temperatures are higher (and the implied stellar radii lower) than expected for a 300 yr old neutron star according to standard cooling models. A steep power law model (photon index 3.8), which might be expected for non-thermal emission from a young pulsar or an accreting compact object, also fits the data. However, the implied column density in this case is inconsistent with that measured independently at radio wavelengths. No coherent pulsations were detected in a 10 ks Chandra/HRC-S observation. The upper limit on the pulsed fraction is <30% for P>100 ms, <45% for P>5 ms, and <70% for P>1 ms. Existing limits on an optical counterpart strongly discriminate against models that invoke accretion onto a neutron star or black hole.
American Astronomical Society Meeting Abstracts #195
- Pub Date:
- May 2000