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Astron. Astrophys. 355, 1041-1048 (2000)

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4. Update of the X-ray light curve of RX J0537.7-7034

For the purpose of the discussion (see next paragraph) of alternative interpretations it seems useful to have the complete ROSAT X-ray light curve available. Though there has been no further ROSAT observation covering RX J0537.7-7034 since 1994 as presented in Orio et al. (1997), we have recalculated the count rates or upper limits, respectively, using the recently improved point spread function fitting and detection algorithms within the EXSAS package (Zimmermann et al. 1994). In addition, we used only PSPC channels 11-50 (corresponding to roughly 0.1-0.5 keV) for the upper limit calculation since the source in its on-state has such a very soft spectrum. Therefore, the intensity numbers of Table 3 differ slightly from those given by Orio et al. (1997). A visual representation of the table data is given in Fig. 6.

[FIGURE] Fig. 6. X-ray light curve of RX J0537.7-7034 as observed with ROSAT. Arrows denote 2[FORMULA] upper limits, and the HRI upper limit on HJD = 2449611 has been transformed into a PSPC count rate upper limit using the conversion factor 7.8 (Greiner et al. 1996).


Table 3. ROSAT X-ray observations of RX J0537.7-7034.
1) Upper limits are 2[FORMULA] confidence, and for the PSPC observations have been calculated using only the soft channels 11-50.
2) HR1 is the normalized count difference ([FORMULA] - [FORMULA])/([FORMULA] + [FORMULA]), where [FORMULA] denotes the number of counts in the PSPC between channel a and channel b.
3) The investigation of this pointed observation has been split for the present paper into the two distinct and widely separated temporal segments.

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© European Southern Observatory (ESO) 2000

Online publication: March 21, 2000