Long term variations in RXJ 0720
 


 
De Vries et al., 2004
Vink, et al, 2004
A gradual, long term change in the shape of the X-ray spectrum AND in the pulse profile

From rev. 78 (13 May 2000) to rev.711 (27-10-2003) the pulse profile become narrower and the pulsed fraction increases from ~20% to ~ 35%
Pulse profile of 0720 in the 0.1-1.2 keV band and hardness ratio. The best sinusoidal fit to rev. 0078 (solid line) is  overplotted on the light curve of  rev. 0711 for comparison.