ROSAT Observations of the Symbiotic Stars PU Vulpeculae and FG Serpentis, and the Cataclysmic Variable V Sagittae

ROSAT PSPC pointed observations of PU Vulpeculae on 1992 November 10-12 UT give a count rate of 4.00 +- 0.75 X 10^-3 cts/s in the energy range from 0.1 to 1.8 keV. The count rate outside this energy range is approximately zero. An analysis of the energy spectrum, with the requirement that the result be consistent with the observed reddening of about 0.50 mag, yields T=0.25 (+0.19, -0.13) keV and log(N_H) = 21.40 (+0.28, -0.35) for a bremsstrahlung emission model. FG Serpentis was not detected during an 8467 s ROSAT PSPC pointed exposure on 1992 March 8-23 UT. Serendipitous X-ray sources detected nearby give an upper limit of ~9.3 X 10^-4 ct/s for the X-ray emission from FG Ser. The post-outburst X-ray fluxes of FG Ser and PU Vul are compared to those of three other symbiotic novae, HM Sagittae, V1016 Cygni and RR Telescopii. The eclipsing nova-like variable V Sagittae was serendipitously observed during the ROSAT exposure of PU Vul and found to have a count rate of 0.013 +- 0.003 cts/s, which is about the same as it showed during Einstein IPC observations in 1979-80. A period of 6.0 hr is detected in the X-ray data; this period is roughly half the length of the observed orbital period of V Sge. (SECTION: Stars)