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 over ~years: BUT 0720!
ÿ No radio
emission ?
ÿ No obvious
association with SNR
ÿ Optically faint