6. Short-term variability
Besides the exponential decline, the soft X-ray flux of RX J0513 shows significant variations of 0.1 HRI counts/s on timescales of hours to days (Fig. 4). A time-series analysis of the detrended HRI count rates, however, reveals no clear periodicity in the range 0.1-10 days. The strongest signal is found at days but corresponds only to a detection. We have arbitrarily phase-folded the residual fluxes on the suggested orbital period of 0.76 days but find no obvious modulation of the light curve neither using the spectroscopic ephemeris (Crampton et al. 1996) nor using the better defined photometric ephemeris (Alcock et al. 1996).
Although our analysis shows that variability on the orbital and possibly shorter timescales may be present, our data coverage is not sufficient to decide whether the flux variations are truly periodic or not.
© European Southern Observatory (ESO) 2000
Online publication: January 31, 2000