Observed variety of timescales in variability of P Cygni

1 P Cygni is a LBV (B1 Ia+) which exhibits photometric and spectroscopic variability.what this book is about 2 We present observational data from two periods (1981–82 and 1989–90) pointing to three different variability timescales. 3 Data sources: a) spectroscopy - our observations at Tartu and results published earlier (Markova, Kolka 1989) b) photometry - our compilation (Kolka, de Groot, Percy 1993). 4 The features measured: a) the brightness (m(V)) in V -filter b) the residual intensity (Rc) and the radial velocity (Vr in km/s) of the absorption trough in chosen spectral lines. 5 Important quasi-stabil variability timescales (see Fig.1, Fig.2) in our data: a) cycle-length 230…240 days in the variations of Rc in Balmer-line H9 correlated with the Vr -oscillations in the same line. The m(V) -curve has regularly local maxima near the moment of residual intensity minimum. The deepening of the absorption trough is related to the higher average level of the brightness. b) cycle-length around 50 days in the behaviour of Rc and Vr in the line HeI3820 (most pronounced in the period 1981 – 82 (Fig.1) when minima in Rc occurred as a rule together with maxima in Vr). This timescale-value is often observable in the lightcurve, too (see also Percy et al. 1988). c) cycle-length 15…20 days is common in Vr -variability of weak lines (e.g. OII3727) and in lightcurve data with sufficient time resolution. 6 e believe the time-dependent intensity of matter outflow is responsible for all variability cycles.