## 7. Quiescent X-ray luminosity and accretion rateV592 Her is in the pointed ROSAT PSPC observation of
Her (obs. id. 201228p),
obtained on 1-4 September 1992, but was not detected in this 5563 s
observation, with a upper limit to
the count rate in channels 11-240 of
cts s We can crudely estimate the disk luminosity and the mass-transfer
rate by assuming that the optical flickering is due to a classical
"bright spot" radiating at the canonical temperature of
K: if the bright-spot Given the fact that the accretion disk is not in a steady-state, that the inclination and white dwarf mass are not known, that Eq. (2) is based on very crude approximations, and that the inner disk may also contribute to the flickering, this is not in contradiction with Eq. (1). We can also estimate the mean long-term transfer rate from the outburst energy and recurrence time: With , (as appropriate for a blue outburst disk; Paczyski & Schwarzenberg-Czerny 1980), and d, we obtain a mean outburst luminosity of and, for a recurrence time yr, a transfer rate The mean mass transfer rate inferred for short-period CVs is (Patterson 1984), but this is dominated by systems with hydrogen burning secondaries. With a degenerate brown dwarf secondary the mass-transfer rate driven by gravitational radiation at hr and for is With a relatively massive white dwarf , , , and are all consistent at . © European Southern Observatory (ESO) 1999 Online publication: February 23, 1999 |