ÿ Soft X-ray sources in
ROSAT survey
ÿ BB-like X-ray spectra, no non thermal
hard emission
ÿ Low absorption, nearby (NH ~1019-1020 cm-2)
ÿ Constant X-ray flux on time scales of
years
ÿ Some are X-ray pulsars (3.45-11.37
s)
ÿ No radio emission ?
ÿ No obvious association with SNR
ÿ Optically faint