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
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