The delta Scuti star DK Virginis (HR 5005) revisited

An analysis of Hp photometry of DK Virginis is carried out. The analysis re veals two frequencies, f(1) = 9.2095 and f(2) = 7.5764 cycles day(-1). Thes e values turn out to be good enough to bridge the gap between the two avail able series of ground-based data, obtained in 1973 and 1980, so that the fr equencies can be refined. The refined values are equal to 9.20945 and 7.576 41 cycles day(-1). The corresponding V amplitudes amount to 8.6 +/- 0.4 and 11.1 +/- 0.4 mmag, and the epochs of maximum light are equal to JD. 2,441, 715.0294 +/- 0.0008 and 2,441,715.1205 +/- 0.0007. The synthetic light curv e, computed with these parameters, correctly reproduces the large light ran ge on JD 2,439,177, the night in 1966 when the star was discovered to be va riable, and the small range on JD 2,440,682, when the light variation was n ot detected. In this way, all photometric observations of DK Vir are accoun ted for, indicating that the two frequencies have not changed appreciably s ince 1965, and that the V amplitudes were constant over the interval from 1 965 to 1980. Using a photometric effective temperature and Hipparcos parallax, we plot t he star in the H-R diagram. Comparison with evolutionary tracks then shows that DK Vir is at the end of the main-sequence stage of its evolution or sl ightly beyond, with a mass of 2.1 M. or somewhat smaller. Finally, an exami nation of linear nonadiabatic pulsation frequencies of modes with l less th an or equal to 2 indicates that the two observed modes cannot both be radia l, and that the f(1) mode must be nonradial if the star is still on the mai n sequence. The properties of the Hipparcos spectral window are examined in the Appendi x.