We have presented spectroscopic and photometric measurements of the cataclysmic variable WW Cet. The spectroscopy shows the system in three different states. We have extracted radial velocities and compared them to other authors to derive the orbital period with a precision of days. We are thus able to constrain the range of possible orbital periods to two choices and , of which the first one seems somewhat more probable. Another time-resolved spectroscopic study in the future might solve this alias problem definitively.
With these periods we have calculated several system parameters for WW Cet. The derived mass and radius for the secondary are in good agreement with the assumption of a main-sequence star of spectral type M2.5 as already pointed out by HSJ90. The corresponding parameters for the WD suffer from greater uncertainties (due to the large error in and the uncertain mass-radius relation), but are still in a very reasonable range. Finally, we derived an inclination for the system.
The photometric data reveal variations on timescales 1.4 and 0.9 hrs which are periodic with the orbital period and are identified as a main and an intermediate hump. These features as well as the absence of an eclipse support the medium inclination derived by us. Comparison with other photometries showing the system at different brightness levels lets us suspect a temporary phenomenon which varies with the brightness of the system as has been also observed in other CVs.
When applying the spectroscopic ephemerides, these humps appear at very unusual phases which are not conform with the place which is normally inhabited by the hot spot. On the other hand, the spectroscopic data reveal an enhanced H emission region in the direction of the phases of the photometric features when they are folded with period . We therefore believe that this phasing is real.
Future photometric observations of WW Cet in different brightness states as well as time-resolved spectroscopy with better S/N and time resolution and following Doppler mapping should provide more information on the phenomena described in this paper. Simultaneous observations of absorption and emission lines would allow a direct comparison of their phasings and thus clarify whether the wings of the emission lines really represent the motion of the WD or if additional emission disturbes them as well.
© European Southern Observatory (ESO) 1997
Online publication: April 8, 1998