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Astron. Astrophys. 358, 600-604 (2000)

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5. HRI observations

As mentioned in Sect. 2, two ROSAT HRI pointed observations were performed, centered on the PSPC survey position (see Table 4 for a summary). Both sources varied in intensity by a factor of two between the observations, seven months apart. Also on short time scales of hours both sources are variable with intervals with source count rates consistent with zero. The HRI light curve for RX J191059.6+285639 (the cataclysmic variable) obtained from the April 1997 observation is shown in Fig. 6. A temporal analysis to search for periodic modulation in the range of 1 to 1000 s yields no significant period with an upper limit for sinusoidal variations of 23% (semi-amplitude modulation). This is consistent with our optical results that RX J191059.6+285639 contains a non-magnetic white dwarf. The X-ray light curve folded with the orbital period of 3.43 h shows no significant variations, however the statistics is too low to rule such completely out. The flaring-like activity seen in Fig. 6 is probably unrelated to the binary orbit.

[FIGURE] Fig. 6. Background subtracted soft X-ray light curve of RX J191059.6+285639 between 1997, April 7, 10:05 UT and April 10, 23:06 UT. The last minor part of the observation which followed after a gap of 13 days is not shown. The time resolution is 400 s


Table 4. HRI observations

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© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000