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Session 113 - Old Worn-Out Stars.
Oral session, Thursday, January 16
Piers 2/3,
In quick succession, four young cooling neutron star candidates have been discovered in supernova remnants. These objects show no direct signs of magnetospheric activity. Here, we present a \sim 20 ks Advanced Satellite for Cosmology and Astrophysics (ASCA) observation of the intriguing X-ray source \ee. The source is situated near the center of \pks, one of the original barrel-shaped supernova remnants (SNR). ASCA and ROSAT PSPC data are very well described by a blackbody model of temperature kT = 0.28 keV with a foreground absorbing column of N_H = 4 \times 10^20 cm^-2 in the range 0.1 - 10.0 keV. At its likely distance of 2 kpc, the luminosity L_X \sim 10^33d_2^2 erg s^-1 implies a radiating surface area A \sim 30d_2^2 km^2, which is significantly less than the total area of a canonical neutron star. Despite the large number of detected photons we see no evidence for rotationally induced X-ray pulsations. Surprisingly, no pulsar-like behavior is found in \ee, except that a faint radio nebulosity surrounding it may well be a pulsar-powered plerion. We deduce that the neutron star may have born spinning very slowly (a birth period P \sim 0.5 s) and is a weak pulsar, strengthening our belief that the observed radiation is indeed due to surface cooling. We suggest that these cooling objects may be born with large \simgt 10^13 G fields and slow rotation. Such objects are candidates for ``injection'', a thorny issue in pulsar astrophysics.