The striking case of RX J1856.5-3754
n500 ks DDT Chandra exposure
(i) RX J1856.5-3754 has
a featureless X-ray continuum
(ii) better fit with a
simple bb than with more sophisticated
atmospheric models (Burwitz et al 2001, Drake et al
2002, Burwitz et al, 2002)
XMM-Newton and Chandra spectra of RXJ1856 together with the best single
blackbody fit to each instrument (see table).