Spectral variations with pulse phase
ÿ Hardness ratio
is max at the pulse maximum: counter-intuitive!
ÿ Same observed
in RX J0420 and RXJ0806 (Haberl et
al., 2004, in prep.)
Þ Beaming effects ? (Cropper et al. 2001)
Þ Phase-dependent cyclotron absorption? (Haberl et al., 2003)
ÿ dP/dt measured in 1 case: the brightest pulsating source RXJ0720.
ÿ dP/dt
= 1.4 ±
0.6 x10-13
s/s Þ B »
(2.8-4.2) x 1013 G ; Ecp »
0.2-0.3 keV (Cropper et al. 2004 in prep.)
RXJ 0720
RBS 1223