Astron. Astrophys. 342, L45-L48 (1999)
8. Conclusions
We have presented optical and X-ray photometry of V592 Her in
quiescence obtained one year before the 1998 outburst. The
R-band brightness of ,
flickering amplitude of mag, the
large outburst amplitude of 10 mag, and the blue
|| color of
are consistent with a nearly bare
white dwarf with a low temperature of
K and a distance of
pc. Combining the empirical
-
relation for dwarf novae with the observed
, and the correlation between
and the outburst recurrence time
with the observed , we have shown
that the distance is likely to be significantly less than 1 kpc.
Given an orbital period of 1.5 hr, the presence of a main sequence
secondary is unlikely, because the implied distance of
pc is very difficult to reconcile
with the observed outburst and quiescent magnitudes. This suggests
that V592 Her contains a degenerate brown dwarf secondary and has
passed through the period minimum of CVs, as has been speculated
lately to be the case for TOADs in general (e.g. Politano et al.
1998). The low mass-transfer rate expected for a brown dwarf secondary
is consistent with the non-detection in X-rays, the low bright-spot
luminosity inferred from the small-amplitude flickering, the long
inter-outburst timescale, and the low white dwarf temperature.
© European Southern Observatory (ESO) 1999
Online publication: February 23, 1999
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