The multiple spectroscopic and photometric periods of DI Cru (=WR 46)

In an effort to determine the orbital period of the star DI Cru, we made photometric and spectroscopic observations of this object between 1996 and 2002. The star is highly variable on short (few hours) as well as on long (few months) time-scales. The optical spectrum is rich in strong emission lines of high ionization species. Temporal Variance Spectrum - TVS - analysis shows that the He II 4686A line has P Cyg-like variable absorption, while NV 4603/19A lines have a strong and broad variable component due to the continuum fluorescence from a source (stellar atmosphere/optically thick wind) of variable temperature. We also show that the object has variable degree of ionization, probably caused by wind density variation. The star presents multiple periods in radial velocity and photometry. We derived, from our data, a main radial velocity period of 0.3319 d with an amplitude of K = 58 km/s. When at intermediate brightness level, this period is also seen in the photometric measurements. When the star is at bright phase, the photometric variations do not present the same period. Photometric periods ranging from 0.154 to 0.378 d are present, consistent with observations reported by other authors. Besides the 0.3319 d period other spectroscopic periods are also seen. On distinct epochs, the periods are different; Marchenko et al. (2000) interpreted the 0.3319 d period as the orbital one. Although we do not discard this possibility, the true binary nature (e.g. long term coherence or detection of a secondary star) has not yet been demonstrated. DI Cru is a Population I WR object. Given the similarities (e.g. multiple periods likely due to non-radial oscillations), it could be interpreted as a luminous counterpart of the qWR star HD 45166.