2000A&A...364..199K

New CCD observations of the pre-cataclysmic binary HW Virginis are presented and discussed. The R-filtered CCD photometry was supplemented with medium-band (Cousins VRI) spectrophotometry based on low-resolution objective-prism spectra. The period variation is reanalysed by means of the standard O-C technique. The new data support the conclusions of Kilkenny et al. (2000Obs...120...48K) on the strong and continuous period change. The long-term period variation can be described approximately with two linear branches in the O-C diagram corresponding to a sudden period jump between two constant periods around JD 2448500 (1991). Additional smooth small-scale changes in the period distort the linearity. The present data do not support the hypothetical light-time effect of Cakirli & Devlen (1999A&AS..136...27C). The eclipse depths in V, R, and I do not show colour dependence, which suggests negligible continuum variations due to the cool secondary component in the far-red region (up to 8800Å). The magnitude of the reflection effect was used to estimate the mean effective temperature of the illuminated hemisphere of the secondary. The result is 13300±200K or 11000±200K, depending on the primary temperature (35000K or 26000K). An albedo near unity is implied for the cool component.