Central Compact Objects in Supernova Remnants

George Pavlov

Pennsylvania State University


X-ray observations show puzzling compact objects near centers of some SNRs. Having X-ray luminosities in a range of 1032 - 1034 erg/s, they have not been seen in radio, optical, and gamma-ray bands, and they do not show pulsar wind nebulae expected for active radio and/or gamma-ray pulsars. Their X-ray spectra are predominantly thermal, with temperatures of a few million kelvins and emitting areas much smaller than the surface area of a neutron star. About eight such sources are currently known, and it is not clear whether they constitute a uniform class or it is a collection of physically different objects. It seems plausible that at least some of these sources are related to magnetars, but no firm confirmation of this hypothesis has been obtained. I will give an overview of the available observations of the whole class and discuss possible interpretations of their properties. I will also present our recent deep X-ray and optical observations of two best-studied (and most puzzling) CCOs, with most distinct properties: the central source of the Cas A SNR and the famous 1E 1207-5209 in the SNR G296.5+10.0. The Cas A CCO is the youngest member of this class, and its properties most strongly resemble those of magnetars, although its period has not been detected yet. In contrast, 1E 1207-5209 shows pulsation with a period of about 424 ms, which varies with time nonmonotonically, possibly because it is in a wide binary system with a low-mass companion. This is the only CCO from which spectral lines have been detected, which provides an opportunity to measure the gravitational redshift at the neutron star surface. I will discuss the properties and possible interpretations of these puzzling lines.

Go back to the program page