[SN, SNR, and Isolated NS -- Oral ]

A Carbon Atmosphere for the Cassiopeia A Neutron Star

Craig Heinke, University of Alberta
Wynn Ho (University of Southampton)

The nature of the central compact objects in supernova remnants, showing thermal spectra but no radio pulsations, is a major mystery of the Chandra era. The youngest known CCO in Cassiopeia A is perhaps the most mysterious, as spectral fits with single-component models have given emitting areas too small for neutron star radii, while a hot spot should produce pulsations that have not yet been detected. We have produced a variety of light-element atmosphere models for neutron stars, and found that only unmagnetized carbon atmospheres provide both acceptable fits to the Cas A CCO spectrum (T~1.5e6 K, R~12 km) and radius constraints consistent with modern NS models. Our result has ramifications for the evolution of NS surfaces, NS thermal evolution, and constraints on NS interior structure.